# Gravity Hot Water Return Pipe Questions



## Don The Plumber (Feb 14, 2010)

I have to replace a water heater, in the next few weeks, (it's not leaking, but is old & customer wants it replaced when they will be off work), that has a gravity return line (no pump) connected up to drain on heater. This is a nat gas 50 gal heater. I personally have never had luck with gravity returns, but many people do, I guess.
This customer claims that the return works great, yet when I was over there yesterday, for something else, I looked at the heater & the return at heater was not hot. It also does not have a check valve.
Questions #1 -Do I install a check valve when I install the new heater? This would be a swing type CV.
#2- If I do install a CV in the return line, will this possibly cause the gravity system "that works so great now" to not work so great?:no: :yes:
#3- What would you do? Pump is out of the question, cuz this customer is cheap, & as I said, claims that gravity system performs well now.:confused1:


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## ILPlumber (Jun 17, 2008)

Yes / no / yes

Pull the heat trap out of the WH outlet..........


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## 1703 (Jul 21, 2009)

I'm gonna disagree with Matt and say a check valve can stop the circ line from working.

The reason I say this is I installed one once in the exact situation that you have and I killed the circ line.

Some guys will use a ball valve instead, throttling it down to almost nothing.

Some guys will take the swing check apart and drill a hole in the swingy part.


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## OldSchool (Jan 30, 2010)

a mono flow tee might be your best way


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## OldSchool (Jan 30, 2010)

Don The Plumber said:


> This customer claims that the return works great, yet when I was over there yesterday, for something else, I looked at the heater & the return at heater was not hot. :confused1:


The return line will more than likely never get hot.... it is by convection... only cold or cool water will be going back to the tank.

The hot will only rise to the highest point and when cooled off it will drop back to the tank.


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## ILPlumber (Jun 17, 2008)

They work flawlessly. Especially in multi-story homes with the WH in the basement.


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## Don The Plumber (Feb 14, 2010)

OldSchool said:


> a mono flow tee might be your best way


Where would you put mono flow tee, at the drain valve? Do they even make mono flow tees anymore? I don't think I ever seen a 3/4" mono flow tee.


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## Don The Plumber (Feb 14, 2010)

Colgar said:


> I'm gonna disagree with Matt and say a check valve can stop the circ line from working.
> 
> The reason I say this is I installed one once in the exact situation that you have and I killed the circ line.
> 
> ...


I like the idea of drilling a hole in CV. That may be the way I go, cuz I just can't see how that gravity could actually push water through that CV. 
I also like Matts suggestion about removing the heat trap, if there is one. I'm not sure if the heaters I use have those or not, but I'm going to find out. Thanks, & keep the advice coming everyone.


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## RealLivePlumber (Jun 22, 2008)

Sure, they still make mono flo tees. 

Any restriction in the piping will cause it to not flow. Do not install a check valve. Remember, it will take the path of least resistance. Think of a flow check on a boiler. If you open the gate with the screw on the top, that thing will flow water like a champ, all day and night. ( I left one open one time, by the time I got the call the next day, and got over there, it was 90 degrees in the house, and the vent connector was about cherry red. )

Why not just put it back like it is, if the ho says it works.


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## Don The Plumber (Feb 14, 2010)

RealLivePlumber said:


> Sure, they still make mono flo tees.
> 
> Any restriction in the piping will cause it to not flow. Do not install a check valve. Remember, it will take the path of least resistance. Think of a flow check on a boiler. If you open the gate with the screw on the top, that thing will flow water like a champ, all day and night. ( I left one open one time, by the time I got the call the next day, and got over there, it was 90 degrees in the house, and the vent connector was about cherry red. )
> 
> Why not just put it back like it is, if the ho says it works.


With my luck, I will get a call back, if I install it the same way, although I'm leaning that way. I just can't imagine that water not flowing back out the return, the wrong way, if there is no CV. Then causing hot & cold sandwiching, I guess is how I describe it.


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## OldSchool (Jan 30, 2010)

Don The Plumber said:


> Where would you put mono flow tee, at the drain valve? Do they even make mono flow tees anymore? I don't think I ever seen a 3/4" mono flow tee.


Where is the return connected presently?


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## Don The Plumber (Feb 14, 2010)

OldSchool said:


> Where is the return connected presently?


At the drain on front of heater.


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## OldSchool (Jan 30, 2010)

Install it the same way it is then nothing else needed


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