Quote:
Originally Posted by rsmurano
You need much more than just putting a pump o the hot water line, you need all the plumbing that goes with it. If you stick a pump on the hot water line by itself, you will blow the line apart overtime time.
Also you don’t use the cold water line as the return line. If this was the case you would never have cold water.
A hot water recirculating system is 1 big loop of the hot water line with drops for each kitchen and bath. The water from the heater flows in a circle keeping the water at a temperature you program at the pump, not at the heater. If you set the water heater at 120 and the recirculating pump is set at 122, your water will run constantly because it’s trying to heat the water to something higher than your heater. Don’t do this. I always set my pumps to a temp of 3-5 degrees colder so the pump would shut off for periods and when we needed water, it was only a couple degrees off the max setting ofthe heater and we had instant hot water at every location
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You are not describing a Watts system which has been retrofitted to an existing house. The Watts system uses a low pressure pump to move water from the water heater through the hot water line to a manifold (valves) placed at the faucet or fixture furthest from the water heater. When the cold side of that faucet or fixture is turned off, the valves in the manifold direct the hot water into the cold water line which carries it back to the water heater. If the cold side of the furthest faucet or any cold side of any faucet in the system is open, the valve in the manifold closes and the hot water flow is stopped. The Watts pump is very low pressure, 2-3 lbs, and the pressure in the cold line is 30-50 lbs, which means that flowing cold water will always control the valve in the manifold.
In contrast to a Watts pump that has been fitted to an existing system, in new construction a separate return line (the 3rd line-hot, return, cold) is installed and the water being pushed by the Watts pump is returned to the water heater by the separate return line and not the cold water line.
When the Watts system is installed in an existing house and the cold water line is used as the return line, the water at the faucet on the cold side will be warm when first opened and will remain warm for the 30 or so seconds it takes for cold water to purge the hot water which has been running in the line. This is the exact opposite of waiting for hot water to reach the faucet when there is no recirculating system. I much prefer having hot water in a 2-3 seconds after opening the faucet and waiting 30 seconds for cold water than waiting 30 seconds for hot water.
Existing houses can have a separate return line installed, although it is expensive. Usually, this would be done in a house with a basement where the pipes are readily accessible. When the house is on a slab and the water lines are installed in or under the slab, it is not practical to install a 3rd line, hence, the ingenious manifold made by Watts which directs the hot water being circulated by the Watts pump into the cold water line and then to the water heater in a closed loop.