Re-circulating hot water

[Nathan Pratt]

I built a new house about 2 years ago and was surprised to see an average of 100 gallons of propane per month over three months in the summer ( no heat, only the water heater, dryer and cooktop). Based on my last house I was expecting 20 gallons. I valved off the recirculating pump and the gas consumption went to 15 gallons per month over several months.

I am trying to figure out what is wrong with the systems so I can get hot water to all my faucets. The system was setup in two loops with one running to the master bath ~100 feet and a second running to the kitchen/baths and laundry ~30 feet. The two return loops join just before the pump and water heater. There is no check valve to isolate the two loops. I though that maybe a hot and cold lines got crossed, so I turn off the hot water supply and ran the hot on all the facets to see If I got any water, but I didn’t not get any. The other strange thing that happened is in the master bath there are two shower heads. One runs hot within a minute and the second will never get past luke warm on it’s own. If I also run the faucet with the second shower head then they will both run hot after several minutes. If I turn off the faucet once the shower it hot it will return to warm. The other odd thing is kid bathroom takes longer to get hot than the master when the kids bath is about 20 feet past the T from the secondary loop. In fact if my daughter turns on the hot water when she goes in, it will still be cold when she is trying to wash her hands. I suspect that some of this maybe from two loops not being isolated, but I do not have any ideas on how to track down the problem and fix.

Does anyone have any idea on how much extra propane should be used if the system were operation properly?   I think the pipes are insulated and they used ~3/4 on the supply and ~ 1” on the return.

Thank you

[Retired plbg1Participant]

first hing is return should be 1/2″. Ther should be a balaning valve o each return and branched together and a balaning valve on that line. You do not have the system balanced.

Art Retired Plbg.

[ndroberParticipant]

Thank you. It should like they were only relying on the pump to set the flow direction. It turns out that the is a swing check valve next to the pump but it does not restrict flow between the two lines.

To clarify the luke warm. With the system valved open and pump running everything works fine (except for the $240 extra dollars a month in propane). When the pump is off and the valves left open, every faucet gets cold water. ( the return is attached to the bottom of the hot water heater. There is what looks like a PRV or maybe a burst disk in the upstream side of the pump. It is between the two isolation valves around the pump. No other signs of any flow or pressure control anywhere in the system.

The way I have been using is with the pump off and both the valves closed. ( at least until my wife complained the kids were washing with cold water) This isolates the two return lines from the hot water heater but not each other.

For reference at my kitchen sink closest to the hot water heater ~15′ the temperature is 135 deg. In the mater bath another ~75′ away one shower is 120 deg and the other is 94 deg. The two sinks run at 115 and 110. The bath (separate from the shower) runs at 120 for the main spout and 115 for the hand shower.

I have tried running the hot water and checking the faucets, the hot line stays hot and the cold line cold, so I do not think anything is flowing the other way.

I tried to look at the photos during construction but I could not make sence of what was going on. It looked like there was two hot line running to each fixture, however I would have expected a hot supply manifold and hot return manifold, instead I only found one manifold with about half of the pipe being a large size and half the smaller size.

My brute force solution, is the one one I have right now is to install check valves in the two return lines and use occupancy sensors to activate the pump. I would expect with check valves the system would not pull water from the bottom of the tank and this would minimize the energy waste. My wife and kids are home all day so a time would not due much good.

Thanks

Nathan

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