Downsizing hot water tank

[Arctic Fox]

We have a 40-gallon tank (electric) that is 26 years old and seems to be in perfect working order.

When it does fail, does it make sense to install a smaller one as there are only the two of us?

Most online references say a 30-gallon would be sufficient.

Would it be cheaper to run, or are they all so well-insulated these days...

Thank you

[retiredguy123]

Definitely a bad idea. 40 gallons is a pretty standard size, and a buyer will expect at least a 40 gallon tank. A smaller tank may not even comply with the building code. Any savings on electricity would be minimal. Note that, if you have a large spa type tub, you would probably need a 60 gallon water heater.

[Bill14564]

I assume you mean 30 gallon rather than 3 gallon.

Some thoughts:

- Taking into consideration the expectations of a potential buyer makes sense. You wouldn't want to lose a sale because of this choice.

- Cost may help you decide. A quick search turned up prices in the $500 range for 30 gallon but closer to $400 for 40 gallon.

- Whatever size you buy, you will still need the same amount of energy to heat the water. Using 20gals of hot water means heating 20gals of water again; it doesn't matter if that water goes into a 30 gallon tank or a 40 gallon tank.

- I suspect that the tanks are pretty efficient at holding water at a certain temperature so you wouldn't see much difference, if any, between the 30gal and 40gal tanks. (Note: Unless the 30gal is designed to save space and includes less insulation which would result in costing a little more to hold temperature)

[Topspinmo]

IMO I wouldn’t. You say two people, probably be ok as long as two of don’t take shower right after each other and leave water running the whole time both are showering. If your house like mine I got run shower for 30 to 45 seconds just to get hot water back to master shower. Add time takes two people to shower if they don’t cut water off between washing pretty much use up 20 plus more gallons which means the second person will get Luke warm water. Now if like me I rinse off, shut shower off, wash my face, turn shower on to rinse, shut off while washing my hair, turn on to rinse, shut off while washing my body, then rinse. I haven’t timed and measured but I bet I’m using less than 10 gallons, which 1/4 used just get hot water back there. I don’t think see any benifits using smaller tank?

Probably won’t save anything on water or price of water heater, 40 gallons the popular choice in most cases?

[village dreamer]

and if you have guest with a 30 gal , and try to take 4 showers in a row someone's getting a cold shower. stay with a 40 gal. water heater.

[LeRoySmith]

I rinse off, shut shower off, wash my face, turn shower on to rinse, shut off while washing my hair, turn on to rinse, shut off while washing my body, then rinse.

Dad, is it you?

[retiredguy123]

OP, apparently the code does not require a specific water heater size. But, if you do downsize the water heater tank, I would suggest that you provide full and clear disclosure to a buyer. Otherwise, you could face a lawsuit for deviating from the builder's standard size.

[Stu from NYC]

IMO I wouldn’t. You say two people, probably be ok as long as two of don’t take shower right after each other and leave water running the whole time both are showering. If your house like mine I got run shower for 30 to 45 seconds just to get hot water back to master shower. Add time takes two people to shower if they don’t cut water off between washing pretty much use up 20 plus more gallons which means the second person will get Luke warm water. Now if like me I rinse off, shut shower off, wash my face, turn shower on to rinse, shut off while washing my hair, turn on to rinse, shut off while washing my body, then rinse. I haven’t timed and measured but I bet I’m using less than 10 gallons, which 1/4 used just get hot water back there. I don’t think see any benifits using smaller tank?

Probably won’t save anything on water or price of water heater, 40 gallons the popular choice in most cases?

Shower together to save water!:a20:

[Arctic Fox]

Thank you all, as ever, for your sage advice.

Hopefully this one will keep going for a few more years - surprisingly, the insurance company has never raised the issue of the age of our major appliances.

[Arctic Fox]

I assume you mean 30 gallon rather than 3 gallon.

Good spot. Even I'm not THAT frugal on water usage :-)

[tophcfa]

Thank you all, as ever, for your sage advice.

Hopefully this one will keep going for a few more years - surprisingly, the insurance company has never raised the issue of the age of our major appliances.

Hopefully you won’t need a new homeowners policy with your older tank. I am in the process of pricing a new policy since Farmers is dumping us. Insurers require a 4 point inspection that includes the age of the water heater. Ours is 2007 vintage and we are either being denied or charged about an extra $500 unless we replace the water heater. The heater works perfectly fine, but for about $900 it looks like we will be replacing a perfectly functional 40 gallon electric heater with a new model. I wouldn’t consider a 30 gallon for already stated reasons. Plus, when we have guests visit there is a possibility we could run short of hot water and the savings is minimal.

[Topspinmo]

Thank you all, as ever, for your sage advice.

Hopefully this one will keep going for a few more years - surprisingly, the insurance company has never raised the issue of the age of our major appliances.

I’d say you’re on borrowed time!:boom: It could go any day now, 26 years loooooong time for water heater IMO. :shocked:

[Sandy and Ed]

Shower together to save water!:a20:
Nah. Actually uses up more water. Makes us stay in the shower several times longer

[bowlingal]

30 gal and 40 gal electric are the same price according to Mike Scott Plumbing

[Polarlys]

To Arctic Fox, Sorry you are late to the game. The insurance companies have already caught up to this topic. We had to send them a photo of our water heater prior to the approval of our policy application. This was almost 3 years ago.

[Cliff Fr]

We have a 40-gallon tank (electric) that is 26 years old and seems to be in perfect working order.

When it does fail, does it make sense to install a smaller one as there are only the two of us?

Most online references say a 30-gallon would be sufficient.

Would it be cheaper to run, or are they all so well-insulated these days...

Thank you

I woukd stick with 40 gallons. It might be more efficient than your old one that may have a build up of sediment inside. Your homeowners insurance company will like that you replaced the old one also. We recently replaced ours. We looked at the heat pump type water heaters but decided theirs too much to go wrong with them and they are expensive. There's talk about the heat pump heaters being mandated by the epa so it's probably a good time to replace yours.

[GizmoWhiskers]

I used to have an 80 gal on a timer before moving here in 2020. It was the best! I had electricion put a timer on the wall for it. Timed it to come on at 5 AM and 5 PM for 2 hours. That thing was great. Always had hot water. Low cost to run it on a timer. Two people in the house (thought of resale on size).

Would love to add a timer to this 14 yr system. Will wait for the tank to RIP. Had instant in my first house here. I don't like instant... wastes 2-3 gal of water waiting for instant to reach the faucets. Would use a garden can to catch the waste for plants.

[rsmurano]

It’s all based on your lifestyle, not 1 size fits all. I would Never go smaller than 60 gallon and I would put a recirculating system in if possible.
Do you and your spouse take baths/showers at the same time or back to back? Do you have guests that all of you take showers/baths back to back? This determines how much hot water you need.
This is why any new home in the last 4 or 5 years (including ours) has a tankless system in place. We can take 1 bath or 4 baths/showers concurrently or back to back with no issues.
The problem with tankless is that they are inefficient when using electricity, they need natural gas to operate best, and gas is only south of 44 (or maybe around 44).
They also make heat pump water heaters that might save you money in the long run, and if you go this direction, I’d probably go with an 80 gallon to be safe.

[Sgt Ed]

We have a 40-gallon tank (electric) that is 26 years old and seems to be in perfect working order.

When it does fail, does it make sense to install a smaller one as there are only the two of us?

Most online references say a 30-gallon would be sufficient.

Would it be cheaper to run, or are they all so well-insulated these days...

Thank you All my life I've had 50-60 gal electric heater. Had 2 boys that knew water never ended. Here in The Villages my heater is gas. Very fast recovering in fact seamless.I just hope I never have to replace it. The heater itself not pricy but installation will ruin a checking account. for just replaced his, for house sale and My neighbor just replaced his to sell the house. Mandatory certified gas techs, Had to redo the exhaust system and several conversions from old system to new codes. All told close to $4k.

[retiredguy123]

It’s all based on your lifestyle, not 1 size fits all. I would Never go smaller than 60 gallon and I would put a recirculating system in if possible.
Do you and your spouse take baths/showers at the same time or back to back? Do you have guests that all of you take showers/baths back to back? This determines how much hot water you need.
This is why any new home in the last 4 or 5 years (including ours) has a tankless system in place. We can take 1 bath or 4 baths/showers concurrently or back to back with no issues.
The problem with tankless is that they are inefficient when using electricity, they need natural gas to operate best, and gas is only south of 44 (or maybe around 44).
They also make heat pump water heaters that might save you money in the long run, and if you go this direction, I’d probably go with an 80 gallon to be safe.
I agree that it is based on your lifestyle, but when you decide to market a house with 2 full bathrooms, an undersized water heater will likely be an issue.

[DrHitch]

if you do downsize the water heater tank, I would suggest that you provide full and clear disclosure to a buyer....deviating from the builder's standard size.

Any home sale, regardless of age of the house, is subject to a buyer's inspection... You should never rely upon what the original developer or builder specifies.

[G.R.I.T.S.]

We have a 40-gallon tank (electric) that is 26 years old and seems to be in perfect working order.

When it does fail, does it make sense to install a smaller one as there are only the two of us?

Most online references say a 30-gallon would be sufficient.

Would it be cheaper to run, or are they all so well-insulated these days...

Thank you

We went tankless.

[lawgolfer]

We have a 40-gallon tank (electric) that is 26 years old and seems to be in perfect working order.

When it does fail, does it make sense to install a smaller one as there are only the two of us?

Most online references say a 30-gallon would be sufficient.

Would it be cheaper to run, or are they all so well-insulated these days...

Thank you

New hot water heaters are highly efficient, both as to their burners as well as insulation. You can go to a 50 gallon heater and have the ability to run the washing machine and dishwasher at the same time you take a shower. What ever you do, don't drop down to a 30 gallon tank.

[DrHitch]

You have options:

1) tanked or tankless. There have been a number of conversations on this forum specific to The Villages about tankless water heaters in the newer sections and their inability to provide hot water quickly.

2) size of tanked water heater... One option that is mentioned by many plumbers is to use a slightly smaller tank and then turn the heat up. Very very hot but use a mixing valve on top of the tank.

[retiredguy123]

Any home sale, regardless of age of the house, is subject to a buyer's inspection... You should never rely upon what the original developer or builder specifies.
I think a lot of home inspectors would not notice that the water heater is 30 gallons and not 40 gallons. They look very similar.

[CybrSage]

Go tankless. I love mine.
In the summer, when it is 100°F outside, the water starts at 100°F, saving electricity. You also save a lot of electricity by not keeping a tank of unused water hot.
It does take longer for the hot water to get to the tub. Rather than the 10 seconds for a tank, it is closer to 40 seconds. Yes, some people do whine and moan about that. For the money savings, it is worth it.

Edit: just checked, my electric bill in June was $55.

[lawgolfer]

We have a 40-gallon tank (electric) that is 26 years old and seems to be in perfect working order.

When it does fail, does it make sense to install a smaller one as there are only the two of us?

Most online references say a 30-gallon would be sufficient.

Would it be cheaper to run, or are they all so well-insulated these days...

Thank you

I neglected to mention that with whatever size tank you settle on, you should add a Watts recirculating pump. If it matters to you, a recirculating pump will pay for itself in reduced water usage over the life of the pump. The beauty of the pump is that you will have near-instant hot water at your shower and faucets. It is a great pleasure to not have to stand off to the side of the shower or outside the shower, waiting for the hot water to arrive.

The Watts pump is an ingenious device that sits on top of the outlet of your water heater. The pump runs at a very low pressure and the electric motor is a synchronous type like those used i electric clocks and cost pennies a day to operate. If you are really frugal, the pump has a built-in timer and you can choose the hours for it to operate.

The ingenious part of the Watts system is that the hot water is circulated or returned to the hot water tank through the cold water lines. This is done by a small manifold installed at the faucet that is furtherest from the hot water tank. When all of the faucets, showers, washers etc. in the house are turned off, the manifold directs the hot water into the cold water line which carries it back to the tank. When any faucet etc in the house is open, the valve in the manifold closes and only cold water runs in the cold water line.

Depending on the model of your house, the incoming hot water line may "split and run hot water in two directions. In that case, you will need a manifold at the last faucet on each line. The Watts pump with one manifold costs around $200. The extra manifold is under $50. They are easy to install for a DIYer, although you do have to lie on your back under the sink to install the manifold. When installed by a plumber at the same time as the new water heater, the additional cost to install the Watts system will be minimal.

[jrref]

Definitely a bad idea. 40 gallons is a pretty standard size, and a buyer will expect at least a 40 gallon tank. A smaller tank may not even comply with the building code. Any savings on electricity would be minimal. Note that, if you have a large spa type tub, you would probably need a 60 gallon water heater.

And a smaller tank may be more money because it's not a standard size that most buy. And it will definetly be a negative when you eventually sell the house.

[Priebehouse]

We just switched to a tankless through the TECO program. After looking into insurance alternatives, some would not quote with our 23 year old water heater. As a snowbird, I was always concerned about leaving with the old one popping and banging, waiting for it to let go. The tankless works great. $26/month for 5 years ain't bad at all. Still takes a minute for the hot stuff to get to the other side of the house, but welcome to Florida water pressure. AND we got the added bonus of a bit of extra storage space in the garage since the tankless is outside. IMO, worth looking into.:thumbup:

[jrref]

Quote "We have a 40-gallon tank (electric) that is 26 years old and seems to be in perfect working order."

So you are one of "Those Guys" who is going to wait till your tank fails to get another and brag that it lasted 30 years LOL

Here is what you need to think about:
1) Unless you are changing the anode rod in the tank every 5 or so years, its long gone and becasue the inside of you tank is now rusting, you are washing and possibly drinking with all that "contaminated" water.
2) Because the tank is literally eating itself from the inside out, when it does fail it has a good chance of being spectacular meaning it's probably going to be a large leak or flood due to all the corrosion.

If properly maintained, meaning yearly flushes and changing the anode rod every 5 or so years I guess it's possible it could last that long but not many ever do both of these maintenance tasks.

Time for a new water heater, if not, please let us know when and how it fails and how much it cost for you to fix all the damage.

[sowtime444]

I don't know if this got mentioned yet or not, but the heat pump hot water heaters have a dehumidifying effect which makes the garage more comfortable in the warmer months (which is almost always).

Also the downside of the recirculating pumps is that if you go to get some nice refreshing cold water, it won't be as cold as you had hoped, and now you have to wait for the cold water instead of waiting for the hot...

[LeRoySmith]

Shower together to save water!:a20:

When we do that someone usually ends up with a sprain and the house smells like Bengay for 2 weeks.

[virtue51]

Most water heaters last an average of 10 years -- it is time to replace your water heater.

[MrFlorida]

Don't forget, you also use hot water for the dishwasher, and washing machine as well as for showers. 40 gallons should be just about right for two people.

[Bill14564]

Most water heaters last an average of 10 years -- it is time to replace your water heater.

I wonder if 10 years is the point when water heaters start to fail or if 10 years is just a "standard" time for replacing a hot water heater. Will they not last 15 years or do they not get a chance to last 15 years because they are typically replaced at 10?

Not that I want to wait to see mine fail, just curious.

[Bill14564]

I don't know if this got mentioned yet or not, but the heat pump hot water heaters have a dehumidifying effect which makes the garage more comfortable in the warmer months (which is almost always).

Also the downside of the recirculating pumps is that if you go to get some nice refreshing cold water, it won't be as cold as you had hoped, and now you have to wait for the cold water instead of waiting for the hot...

Cold water in Florida? We joke about how nice the cold water feels when we go back north.

Another downside of the pumps is additional electrical costs. First, there is a pump that runs frequently to send hot water to the far end of the house. Then, there is the cost of heating the cold(er) water that is pushed back into the tank when the pump runs. The instant hot water might be worth it but there is going to be a cost.

[Harold.wiser]

If it were me I would not downsize.

[Stu from NYC]

When we do that someone usually ends up with a sprain and the house smells like Bengay for 2 weeks.

Hold on for dear life will solve that problem.

[Stu from NYC]

I wonder if 10 years is the point when water heaters start to fail or if 10 years is just a "standard" time for replacing a hot water heater. Will they not last 15 years or do they not get a chance to last 15 years because they are typically replaced at 10?

Not that I want to wait to see mine fail, just curious.

Our experience is 15 years or more.

[retiredguy123]

///

[retiredguy123]

I wonder if 10 years is the point when water heaters start to fail or if 10 years is just a "standard" time for replacing a hot water heater. Will they not last 15 years or do they not get a chance to last 15 years because they are typically replaced at 10?

Not that I want to wait to see mine fail, just curious.
If mine was leaking between 10 and 15 years, I would replace it. Otherwise, I will wait until it is 15 years old to replace. Being in the garage reduces the chance to have major damage when it leaks. Also, I have a battery-operated water alarm in the drain pan, which actually warned me of a pinhole leak in my expansion tank a few months ago. No damage.

[eremite06]

That's Navy water hours.

[shut the front door]

Thank you all, as ever, for your sage advice.

Hopefully this one will keep going for a few more years - surprisingly, the insurance company has never raised the issue of the age of our major appliances.

Why in the world would an insurance company give a flying flip about the age of your appliances? I have never in my life had an insurance company ask me how old my washing machine or water heater is.

[Topspinmo]

Why in the world would an insurance company give a flying flip about the age of your appliances? I have never in my life had an insurance company ask me how old my washing machine or water heater is.

Welcome to Florida and villages. Water leaks can cause thousands dollars in damage and mole problems which could lead to drywall replacement or condemned house. When I had to get new insurance they took pictures of roof, water heater, and air handler. All are possible liability issues for insurance.

[Topspinmo]

Shower together to save water!:a20:

Not really too much in road :22yikes:

[Rocksnap]

Dad, is it you?
It’s a modified Navy shower. Was your dad in the Navy?

[lawgolfer]

Cold water in Florida? We joke about how nice the cold water feels when we go back north.

Another downside of the pumps is additional electrical costs. First, there is a pump that runs frequently to send hot water to the far end of the house. Then, there is the cost of heating the cold(er) water that is pushed back into the tank when the pump runs. The instant hot water might be worth it but there is going to be a cost.

The amount of electricity to run a Watts recirculating pump is so small that it will never be. noticed. Anyone who says differently does not know what they are talking about. The motor in a Watts pump is of the synchronous type that is used in electric clocks. In fact, the Watts pump is a clock as you can set the hours you want the pump to operate, if you are concerned about the small amount of electricity it uses. The pump is VERY LOW pressure-just enough to keep water moving through the line.

If you are so frugal that the cost of electricity to run a Watts pump is a concern the fact that the pump provides near-instant hot water at your faucets and showers will offset the cost of the water you waste while waiting for hot water to arrive at the faucets and showers. As one of the RP's to the OP said, you wait "a minute" for hot water to reach the faucet on the far side of the house.

Whether the Watts pump costs money to operate or it makes for a net savings by way of less water usage, the convenience of having near-instant hot water throughout the house is a wonderful thing to behold. No longer will you stand outside the shower in your birthday suit waiting for the hot water to arrive or inside the shower trying to position yourself in the corner and out of the stream of cold water.

[nancyre]

Better to switch to an on demand water heater - similar to the ones being installed in the southern end of the Villages now. No tank at all.

[jrref]

If mine was leaking between 10 and 15 years, I would replace it. Otherwise, I will wait until it is 15 years old to replace. Being in the garage reduces the chance to have major damage when it leaks. Also, I have a battery-operated water alarm in the drain pan, which actually warned me of a pinhole leak in my expansion tank a few months ago. No damage.

And don't forget the benefit of washing with all that rusty hot water from your tank rusting from the inside out. That stuff gets in your pipes so you are drinking it too. The rust and corrosion can't be seen, but it's there. You should search for hot water tanks on YouTube and watch one where they cut open the tank so you can see what it looks like after the anode rod is long gone.

Also, people might think they are saving money waiting until their tank fails but its just the opposite. Unless you are flushing it every year, there will be a ton of sediment in the tank by year 10 so it's efficiency goes way down, especially if its gas. So the few extra years you might get, you are wasting money using an inefficient heater.

If a new heater costs about $900-$1,200 installed, do the math, you save maybe $200 waiting till year 15 vs 10.

Just something to think about.

[jrref]

Better to switch to an on demand water heater - similar to the ones being installed in the southern end of the Villages now. No tank at all.

If you have an existing hot water tank, its never cost effective to go tankless especially if you are only 2 people living here in the Villages. The initial cost to run a gas line and exhaust to the new tankless can cost 3-4 times the amount of just getting a tank replacement. And there is no benefit going tankless. Currently electric tankless units are not very good and if you do want to make that change, you will need new electric at a higher amperage to run tankless electric.

[jimkerr]

I would stick with the 40 gallon. You’ll end up having too many problems running out of hot water. Personally, I’ll stay with a tankless water heater. It’s excellent especially when company stays here and we are using the shower for 5 or 6 people.

[Rocksnap]

How does your electric water heater defy the laws of physics? ANY hot water line that sits stagnant will start losing its heat immediately when the water usage stops flowing. Electric or on demand, makes no difference. When you first your hot water, it will take time to expell the now cool water in your how water line. Or am I missing something?
I put a thermostat on a on/off switch in the furthest fixture from our on demand water heater. Uses the cold water line as a return loop. I truly have instant hot water with no water loss down the drain. The best of both worlds.

I don't like instant... wastes 2-3 gal of water waiting for instant to reach the faucets. Would use a garden can to catch the waste for plants.[/QUOTE]

[Cliff Fr]

Go tankless. I love mine.
In the summer, when it is 100°F outside, the water starts at 100°F, saving electricity. You also save a lot of electricity by not keeping a tank of unused water hot.
It does take longer for the hot water to get to the tub. Rather than the 10 seconds for a tank, it is closer to 40 seconds. Yes, some people do whine and moan about that. For the money savings, it is worth it.

Edit: just checked, my electric bill in June was $55.

Did you have to run high gauge wire for the electric tankless and a dedicated breaker?

[Maker]

There have been a number of conversations on this forum specific to The Villages about tankless water heaters in the newer sections and their inability to provide hot water quickly.

That statement is inaccurate. A tankless delivers hot water in under 2 seconds. The delay people mention comes exclusively from the longer pipe distance. My tankless is on the outside wall about 4 ft from where the tank would have been placed. That might add 4 seconds to the time either one would have had hot water flowing (into the exact same pipe) to the shower. The total time to get that hot water all the way to the bathroom - on the opposite side of the house - is EXACTLY THE SAME no matter the source.

If you put a tankless electric in, where the tank is now, there is no difference in delivery time. And you get a bunch of storage space too.

Love tankless. No concerns what else might be using hot water. Always hot for as long as needed.

[biker1]

Depending on the capacity, probably 60-100 amps. This is not inexpensive since the wires to support that amount of amperage is costly and depending on the location there could be significant labor costs.

Did you have to run high gauge wire for the electric tankless and a dedicated breaker?

[LeRoySmith]

It’s a modified Navy shower. Was your dad in the Navy?

In the Navy for 18mths and the army for 35 years.

[Topspinmo]

And don't forget the benefit of washing with all that rusty hot water from your tank rusting from the inside out. That stuff gets in your pipes so you are drinking it too. The rust and corrosion can't be seen, but it's there. You should search for hot water tanks on YouTube and watch one where they cut open the tank so you can see what it looks like after the anode rod is long gone.

Also, people might think they are saving money waiting until their tank fails but its just the opposite. Unless you are flushing it every year, there will be a ton of sediment in the tank by year 10 so it's efficiency goes way down, especially if its gas. So the few extra years you might get, you are wasting money using an inefficient heater.

If a new heater costs about $900-$1,200 installed, do the math, you save maybe $200 waiting till year 15 vs 10.

Just something to think about.

I don’t drink hot water let alone water from tap. :sigh:

[Topspinmo]

That statement is inaccurate. A tankless delivers hot water in under 2 seconds. The delay people mention comes exclusively from the longer pipe distance. My tankless is on the outside wall about 4 ft from where the tank would have been placed. That might add 4 seconds to the time either one would have had hot water flowing (into the exact same pipe) to the shower. The total time to get that hot water all the way to the bathroom - on the opposite side of the house - is EXACTLY THE SAME no matter the source.

If you put a tankless electric in, where the tank is now, there is no difference in delivery time. And you get a bunch of storage space too.

Love tankless. No concerns what else might be using hot water. Always hot for as long as needed.

Can they be installed inside house like the garage? Some of older designs only option. My water heater in garage close by front door, so outside unit probably be no go?

[jrref]

I don’t drink hot water let alone water from tap. :sigh:

But you cook with the cold water? You wash with the hot water? The rust and corrosion residue is in all your pipes.

[retiredguy123]

But you cook with the cold water? You wash with the hot water? The rust and corrosion residue is in all your pipes.
I cook with cold water, but I do wash with hot water. But Topspinmo does make a good point. If there is any rust in the water, almost all of it would be in the hot water pipes. The only time hot and cold water is mixed is when it comes out of the faucet, or if you have a recirculating system, which I don't have. I guess you could have your hot water tested to see how much rust is in it.

[Maker]

Can they be installed inside house like the garage? Some of older designs only option. My water heater in garage close by front door, so outside unit probably be no go?

Electric tanks and tankless do not have a vent, so they can go inside. Replacing an electric tank with a tankless can be put roughly in the same location. Although one might want it shifted to the side.

For those with gas, most people use an outdoor tankless in warm climated. However, there are models that can go inside. Current indoor tankless require a fresh air source, and an exhaust. Both are ok with using PVC pipes. 3 or 4 inch dia.
Also, current gas fired tank units would need the same air in&out pipes.
Combustion gasses need to vent outside.