Gravity Hot Water Recirculating Loop Questions

[Ballvalve]

If the circulated water is potable water, the pump must be a bronze or ss body. All of the companies make both iron and bronze pump$. Don't remember is this is strictly a (closed) heating loop, or if it is potable water you're moving around.

If its ductile iron, its as good as bronze. The Grundfos circulators I have used many of have such small wetted area of iron, that it seems totally irrelevant to anyones safety. Maybe you get a few micro grams of iron each decade, less than your multi-vitamin.

 

[Jon229]

I want to run a return line in my 55 yr old Ranch style house in order to use the convection circulation to reduce the waiting time for the hot to travel 50 ft to the far bathroom. My water heater (gas) is lower than the water line.

If I remove the backflow loop on top of my water heater from the hot water outlet in order to allow the convection to work, will the water heater run more often? It seems to me that the water in the tank will cool faster using the convection system. I am wondering if this type of system may have significant energy costs.

Also, I'm planning on using copper for the return, teeing off the existing copper run. Is PEX a reasonable alternative instead of copper for the return? It seems that it would be easier to work with.

Thanks, jon

 

[Sponsor]

 

[Jadnashua]

One study I read about pumped recirculation systems found that, with a timer, so it only ran during normal use hours, the extra run-time of the heater used less energy than what it took to heat the extra gallons of water wasted trying to get hot to the end point of use. Even though the water you run down the drain is not hot, whatever you run down the drain is hot coming out of the tank, and thus, it's the same as if all the water was hot, not just that that gets to the faucet. With recirculation, you don't throw any extra down the drain, but you have the radiation losses. In the test, the radiation losses were less than the waste from throwing that water down the drain. Now, depending on the pattern of use, this could change.

Long answer, but yes, the WH will run more often. If you insulate the lines, it is better. Without a pump, it will work better if the return line has a nice constant slope. Pex is hard to get to run straight. It is a bit better than copper on radiation losses. How well a convection loop will work depends a lot on details of the installation. A pumped system overcomes a lot of errors that might prevent a convection system from working.

 

[Jon229]

it will work better if the return line has a nice constant slope. Pex is hard to get to run straight. It is a bit better than copper on radiation losses. How well a convection loop will work depends a lot on details of the installation.

Thanks. My install will not run a staight, constant slope. At the final 25% or so of the return I will have at least 2 elbows to drop below an electrical panel and then a 45 to get it to the WH where I plan to connect via the drain valve. Now I understand the recommendation to insulate the return line most of the way.

Jon