Swing check valve vs spring check valve for Gravity Fed Hot Water Recirc system

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Hogan

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Hi I got a new tank heater with a Caleffi tank mixer valve also installed on top. This to give us the optionality of turning up tank temp to increase effective capacity.

Plumber tied the return lines (gravity fed, no Recirc pump) right back into the cold water inlet of the tank mixer valve as per the instructions (there is a second inlet on that cold water cross for that purpose). We now figured out that there is no check valve in the mixer itself and so when a faucet is opened in the house, the cold water backflows up those recirc lines which is bad!

So we need a check valve right before the recirc line enters the cold water cross. My question is, if we use a spring loaded check valve will the gravity fed system have enough force to open it so the passive loop can flow? Or do we need a looser swing valve but then my worry is that it gets stuck in open position when the cold water rushes in backwards when water is called at the faucet.

Wondering if anyone has experience or thoughts. Thanks
 

Reach4

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I have read that you want to adjust the angle of the swing check to put the swinger at the critical point.
 

hj

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A spring check valve will NOT open with the very minimal pressure of a gravity system. In fact, it may not even open a swing check which is why there is usually a small hole drilled in the gate to allow flow.
 

John Gayewski

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I only use swing checks on these they work just fine. Any check valve can become stuck open the reason to use a spring check isn't becuse it's less likley to become stuck.

You should also be aware that gravity systems aren't legal and there's a possibility you'll have to add a pump on the future.
 

John Gayewski

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People don't install them correctly and the recirc line becomes a long warm dead leg and promotes bacteria. They are required to have a mechanical pump to force circulation. I'd have to look to cite the code section in the upc. As far as ipc no idea if it's remained legal.
 

Tuttles Revenge

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People don't install them correctly and the recirc line becomes a long warm dead leg and promotes bacteria. They are required to have a mechanical pump to force circulation. I'd have to look to cite the code section in the upc. As far as ipc no idea if it's remained legal.
We can't use gravity / convection style recirculation any more here.. I think it has more to do with energy code than anything. Recircs must be user activated. No timers and not on all the time like a gravity system would be.
 

Hogan

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Hmmm interesting re no longer code

Mine was set up 20 yrs ago. I don't think it ever worked well because one pipe was never warm and the other was slightly warm

I was considering adding a Recirc pump but didn't want to spend the money and never really had an issue waiting 30 secs for the water to get warm upstairs

I also was worried about combining the recirc pump with the Caleffi tank mixing valve because the guy installed the return line into the cold water inlet. I've seen that doing this with a pumped hot water recirc can just let the valve drift upwards to the max temp of the tank which is dangerous of course and also negates the reason for having the mixing valve in the first place. I guess he could repipe the recirc into the bottom of the tank and just have the cold water feed go into the mixing valve.

I guess for now I can just ask him to install the swing check on a horizontal section of that recirc line and see whether that can let us open the ball valves on those lines yet stop the backwards cold water flow. I am on his dime right now since he forgot to do this. Or would y'all advise me spending more money to have him add a recirc pump and repipe the recirc line into the tank drain at the bottom? If I never minded the short wait for the past 20 yrs are there other reasons I should spend this money? (Bacteria argument for example)
 

Hogan

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What is difference between a user having to press a Recirc button vs a user opening the upstairs faucet for 30 secs to let hot water run up? Just the gallon of wasted water?
We can't use gravity / convection style recirculation any more here.. I think it has more to do with energy code than anything. Recircs must be user activated. No timers and not on all the time like a gravity system would be.
 

Tuttles Revenge

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What is difference between a user having to press a Recirc button vs a user opening the upstairs faucet for 30 secs to let hot water run up? Just the gallon of wasted water?
In all recirc systems, whatever energy is stored in the water being recirculated is not being lost down the drain. So less energy to get the recirculated water back up to temp. Obviously the gallon or so water that isn't just dumped. And vs a timer or on all the time, theres a lot of standby heat loss that is prevented. At least thats the idea.

We've installed a few now but too early to have gotten feedback on how the customer feels about them for me to have any anecdotal evidence.
 

Hogan

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In all recirc systems, whatever energy is stored in the water being recirculated is not being lost down the drain. So less energy to get the recirculated water back up to temp. Obviously the gallon or so water that isn't just dumped. And vs a timer or on all the time, theres a lot of standby heat loss that is prevented. At least thats the idea.

We've installed a few now but too early to have gotten feedback on how the customer feels about them for me to have any anecdotal evidence.

Interesting

Im sure smarter people have done studies but there would be a lot of heat loss from the copper pipes by running a recirc system even if on a timer for a couple hours a day. You are constantly keeping hot hot water in the lines which will lose heat from the copper, and it may be running that heat for hours per day just to be ready and hope to avoid someone sitting at the tap upstairs for 30-45 seconds. In our family we aren't so perfectly scheduled that everyone takes a shower between a 1 hour period in the morning (and if we did then the pipes would generally stay warm anyway after the first user). Sometimes evening shower or bath for kids. So I guess either there is a "button" that could be pressed somewhere to run the recirc pump or otherwise needs to be set to run intermittently in various windows during the day. And if I left the piping into the mixer valve then I also would need to have him add an aqua stat so the pump doesn't run too much and creep the valve up.

I had these gravity recircs for 20 yrs piped to the bottom of tank. No idea how much flow there was, and also it is certainly possible that was also back-feeding up the recirc lines when a faucet was opened and I didn't know it. I don't think there were check valves on the old setup
 

John Gayewski

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The control method would be an aquastat. Which stays hot all of the time and doesn't save energy. An aqua stat only makes sense on a high temp system in my opinion. Hot buttons are silly in my opinion. Wiring it to the bathroom light makes sense some of the time. Otherwise an aquastat is gonna be the primary control.

Your only losing energy from about late Sept to early May (in my portion of the country) anyway. The rest of the year is heating season and the energy is used to reduce the heating load. If someone were worried about heat loss for 4 months out of the year, an insulated line reduces the heat loss a lot. Most insulation is done poorly and doesn't do the job it should, but a properly insulated line doesn't give off much heat.
 

Hogan

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The control method would be an aquastat. Which stays hot all of the time and doesn't save energy. An aqua stat only makes sense on a high temp system in my opinion. Hot buttons are silly in my opinion. Wiring it to the bathroom light makes sense some of the time. Otherwise an aquastat is gonna be the primary control.

Your only losing energy from about late Sept to early May (in my portion of the country) anyway. The rest of the year is heating season and the energy is used to reduce the heating load. If someone were worried about heat loss for 4 months out of the year, an insulated line reduces the heat loss a lot. Most insulation is done poorly and doesn't do the job it should, but a properly insulated line doesn't give off much heat.

Im not exactly following your point about Sept to May but in any case I guess what I'm saying is I'm not sure I really care about having some pumped system on the recirc. If it hadn't been for someone mentioning that it's not code and has bacteria issues potentially I wouldn't have even thought along those lines.
 

Hogan

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I just Googled. 50 feet of 1/2 inch pipe holds a whopping half gallon of water. So yes we are allowing a half gallon to cool off and lose it's energy at a time. I would think it would be actually MORE inefficient to keep running really hot water thru that pipe for hours of the day as the hotter the water, the more temp it loses to temp differential. It's like running hundreds of gallons of hot water thru a cooling radiator aka your Recirc piping just so you don't need to wait 30 seconds for hot water to come
 
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