[retiredguy123]

Originally Posted by Sweet Caroline

We have had an after market installation for years and love it, set on a timer. Had the plumber install an electric box in closet in garage. Yes, the cold water line is warm but I don't drink out of that faucet so that is ok. After it runs for a while it becomes cold. Funny thing is that I have a spot in my living room tile floor that stays warm!!

It sounds like you may have a leak. One way to check is to turn off all water in the house and see if the outside meter is running.

[SoCalGal]

Query: The plumbers roughed-in the plumbing for our new home. We opted for recirculating hot water for our tankless heater. How are these things plumbed for new construction?

Answer: In new construction, plumbing for a recirculating hot water system with a tankless water heater involves a few key steps to ensure efficiency and functionality:

Rough-In Plumbing:
Initial Setup: The rough-in phase begins after framing but before wall covering. Plumbers install the main water supply lines, drain lines, and vent stacks. For a recirculating system, this includes planning for the hot water loop.

Supply Lines: For a tankless heater, both cold and hot water supply lines are run to where the heater will be installed. This includes ensuring there's a main shut-off valve and possibly isolation valves for easier maintenance.

Recirculation System Installation:
Dedicated Return Line: A common method involves installing a dedicated return line for the hot water. This line runs from the furthest fixture back to the tankless water heater. This setup allows for the hot water to circulate continuously or on-demand back to the heater, keeping the water in the pipes hot. This system typically requires more planning and piping during the rough-in phase, as it involves adding an extra pipe.

Pump Placement: The recirculation pump is generally placed near the water heater on the return line to push the cooled water back into the heater for reheating. If a timer or on-demand system is used, this can be controlled to run only during peak usage times, saving energy.

Tankless Water Heater Considerations:
Positioning: The tankless heater should be placed in a location that minimizes the distance the hot water needs to travel to fixtures, which can be challenging in larger homes. However, with a recirculating system, this issue is mitigated since the water stays hot in the loop.

System Integration: Ensure that the tankless water heater can handle the constant demand of a recirculation system. Some tankless units have built-in recirculation features or are designed to work with external pumps. Check compatibility with your specific model.

Piping and Insulation:
Pipe Material: Use materials like PEX or copper for durability and efficiency, with PEX being popular due to its flexibility and ease of installation.
Insulation: Insulating the hot water pipes is crucial to reduce heat loss, especially in the recirculation loop, ensuring the water remains hot as it travels through the house.

Regulations and Testing:
Compliance: Ensure the installation complies with local building codes, particularly regarding energy efficiency and water conservation.
Testing: After installation, the system should be pressure tested to check for leaks, especially before covering the pipes with drywall or other finishes.

This setup ensures that hot water is available almost immediately at every fixture, reducing water waste and enhancing user convenience. However, remember that while a recirculating system with a tankless heater can be highly efficient, the initial setup and additional piping can increase costs and complexity.

Source: GrokAI, now free to everyone without a subscription

[Marathon Man]

Originally Posted by Kenswing

Only the tank is now at every point of use inside the house instead of in the garage. And your tankless will never run out of hot water.

An uninsulated tank.

[SoCalGal]

Originally Posted by larrycrilley@gmail.com

I copied and pasted your post directly into Chat GPT. It provides a direct answer instead of providing many links (and ads) to help you search for the answer.

ACCORDING TO ChatGPT -

I think you'd like GrokAI better. xAI

[ltcdfancher]

Had the floorplan been different such that the master shower was closer to the heater, then I would not have opted for the recirculating pump either. Alas, the shower is quite far.

[rjm1cc]

No experience. I would think the tankless system would be on 24 hours a day. Seems like a very big problem. I have a regular hot water tank and a pump to circulate the hot water. It works on a timer so I only set it to run a couple of times during the day - when we get up, bed time etc. - and when it is freezing I will run it once or twice in the early mornings on freezing days. (cold water return line helps here) Instead of a timer you could use a smart plug and your phone. I circulate back through the cold water pipe. Not a problem sine I do not run it all the time. But if I did it would be a problem as the water would be too warm. For your system you need a way to turn it off and on when you need it. Might take a minute or two to get hot water so you would have to turn it on before you needed it.
How are the pipes protected from freezing assuming the unit is mounted outside?

[Justputt]

Two considerations with tank or tankless, without a continuous recirculation pump, there's no "instant hot water." First, a tankless heater's heat exchanger needs to get up to temperature (120F, for most), even if gas. If you put a pan of water on the gas stove and turn it on, the water isn't instantly hot. Second, regardless of the source (tank or tankless), the HW lines are full of cold water that must be displaced. In a recirculation system, it sends the water back to the tank or tankless heater, as applicable. Recirculation is with a separate return pipe OR a thermal bypass valve (several good YouTube DIY videos) located at the sink/shower/tub which send the "unheated" water to the cold-water line and won't shunt water to the HW faucet until it is "hot." I just ran a quick test using my guest bathtub, which I think is furthest from the tankless heater. It took 1 minute to get warm enough at the tube faucet (showerhead flow rate would be lower and usually takes 2 minutes), and it dispensed 10 qt (measured with a 10 qt bucket) in that time. Where I used to work (hospital), they ran the recirculation pump continuously (not cost effective for homes!), so they did have instant hot water. I looked at all the DYI stuff this past summer and decided the cost wasn't worth it since all I was saving was 10 qt of water, as it still takes the same amount of time to heat the water at the source and cycle the cold water from the lines. Additionally, timers are fine, but you're either going to set the timer to start every day at say 7 a.m. or set it to run for a couple minutes every time you flick a switch somewhere in your house. To me, that's just a hassle. IMO, flip the HW on, hit the head or brush your teeth and that should be good enough to at least have comfortable warm water to start.

[ltcdfancher]

Thank you for the analysis using your guest bath as the experiment. Only 10 quarts? That’s surprises me. I’ve not calculated the volume of water in, say, 75’ of 3/4” PVC pipe. When we stayed in a lifestyle villa in Kirsten Villas recently, it certainly seemed longer than two minutes to start a warm shower in the master shower.
At the end of the day, I may not engage the pump. It was an expensive upgrade; that’s certain. But isn’t it better to have it and not need it than to eventually want it and not have it?

[Bill14564]

Originally Posted by ltcdfancher

Thank you for the analysis using your guest bath as the experiment. Only 10 quarts? That’s surprises me. I’ve not calculated the volume of water in, say, 75’ of 3/4” PVC pipe. When we stayed in a lifestyle villa in Kirsten Villas recently, it certainly seemed longer than two minutes to start a warm shower in the master shower.
At the end of the day, I may not engage the pump. It was an expensive upgrade; that’s certain. But isn’t it better to have it and not need it than to eventually want it and not have it?

Approx. 1gal/50ft of 3/4” pipe

My home, horizontal distance from heater to guest bath = 42’. Add vertical distance and it’s close to 50’.

4.5qts to draw warm water to guest bath. I didn’t time it but times will vary with different fixtures.

[Altavia]

Originally Posted by Justputt

...

I just ran a quick test using my guest bathtub, which I think is furthest from the tankless heater.

It took 1 minute to get warm enough at the tube faucet (showerhead flow rate would be lower and usually takes 2 minutes), and it dispensed 10 qt (measured with a 10 qt bucket) in that time.

...

I looked at all the DYI stuff this past summer and decided the cost wasn't worth it since all I was saving was 10 qt of water, as it still takes the same amount of time to heat the water at the source and cycle the cold water from the lines.

Additionally, timers are fine, but you're either going to set the timer to start every day at say 7 a.m. or set it to run for a couple minutes every time you flick a switch somewhere in your house. To me, that's just a hassle.

IMO, flip the HW on, hit the head or brush your teeth and that should be good enough to at least have comfortable warm water to start.

Agree, I did a similar test with similar results.

Also:

Measured close to a 10 degree temperature drop from the water heater to the furthest bath (~70 ft).

The cold water temperature here stays close to 75 degrees. It takes less than 10 min for the hot water lines to return to that temperature.

[Altavia]

Originally Posted by ltcdfancher

Thank you for the analysis using your guest bath as the experiment. Only 10 quarts? That’s surprises me. I’ve not calculated the volume of water in, say, 75’ of 3/4” PVC pipe. When we stayed in a lifestyle villa in Kirsten Villas recently, it certainly seemed longer than two minutes to start a warm shower in the master shower.
At the end of the day, I may not engage the pump. It was an expensive upgrade; that’s certain. But isn’t it better to have it and not need it than to eventually want it and not have it?

A small local tankless heater may be more cost effective solution.

Easy for the kitchen. But for the bath would need power and to be placed before the bath shower and sink faucets.

[PPLEPEU]

There is one more option for improved timing of hot water delivery.

I didn’t want our recirculating pump running 24/7 and we don’t keep a schedule like we did when we were working - but we hated waiting 6-7 minutes for hot water.

So, I rigged up a smart outlet on the recirculating pump. That let me control the pump with Alexa. I set up a routine that turned on the outlet for an hour when we say to Alexa, “Turn on the hot water.”

Works great.

[retiredguy123]

Originally Posted by Justputt

Two considerations with tank or tankless, without a continuous recirculation pump, there's no "instant hot water." First, a tankless heater's heat exchanger needs to get up to temperature (120F, for most), even if gas. If you put a pan of water on the gas stove and turn it on, the water isn't instantly hot. Second, regardless of the source (tank or tankless), the HW lines are full of cold water that must be displaced. In a recirculation system, it sends the water back to the tank or tankless heater, as applicable. Recirculation is with a separate return pipe OR a thermal bypass valve (several good YouTube DIY videos) located at the sink/shower/tub which send the "unheated" water to the cold-water line and won't shunt water to the HW faucet until it is "hot." I just ran a quick test using my guest bathtub, which I think is furthest from the tankless heater. It took 1 minute to get warm enough at the tube faucet (showerhead flow rate would be lower and usually takes 2 minutes), and it dispensed 10 qt (measured with a 10 qt bucket) in that time. Where I used to work (hospital), they ran the recirculation pump continuously (not cost effective for homes!), so they did have instant hot water. I looked at all the DYI stuff this past summer and decided the cost wasn't worth it since all I was saving was 10 qt of water, as it still takes the same amount of time to heat the water at the source and cycle the cold water from the lines. Additionally, timers are fine, but you're either going to set the timer to start every day at say 7 a.m. or set it to run for a couple minutes every time you flick a switch somewhere in your house. To me, that's just a hassle. IMO, flip the HW on, hit the head or brush your teeth and that should be good enough to at least have comfortable warm water to start.

Mine takes less than a minute to get hot water to the shower. But, I have found that, if you can't wait to take a shower, turning on the sink faucet and the shower at the same time will reduce the wait time to less than 30 seconds.

[Rocksnap]

Originally Posted by Wondering

Your new circulating pump is going to be costly to run, even if you have a timer, for certain times of the day, when you need to shower. I had one and disconnected it.

I installed a recirculating pump in my last house. It was 1/5 hp, and was on a timer. How exactly is a 1/5 hp pump going to be costly to operate?

[ltcdfancher]

My suspicion is not the cost of electricity to operate the pump, but the cost of the energy to keep the water hot while the pump is operating.

Thank you to everyone for their thoughts and ideas on my original post. Not yet a full-time Villager, I’m excited to meet my new neighbors that show themselves to be 1) clever, 2) helpful, and 3) articulate.