Gravity fed recirc loop question.

**neverman** · 02-03-2006, 07:19 PM

So the hot water heater was installed today in new construction. Where I expected to see a "check valve" I instead saw a regular valve. I asked the plumber about this and he made a case that without a recirc pump there wouldn't be any flow due to just gravity (overcoming the spring of a check valve) so a valve is placed in the return line. This valve will be used to "balance" the system.

This was explained to me as I raised my only concern... that being the cold water mixing with my hot water when we opened the shower valve which would quickly lead to yucky shower performance. He said there would be minimal mixing (getting the bottom end of the tank) if it was properly balanced. He also stated that it would require about 2 hours between tweakings of that valve. I'm pretty confident in his opinion and his explanation of why no check valve could/should be used but I figured I'd run it by you guys.

The recirc line travels to the master shower which is at the farthest corner of the house from the water heater, the recirc line then travels up into the actic at the last manifold before the shower, this whole line is insulated and most of it is also covered by actic fill or sandwiched between 2 floors of the house.

I guess what I'm wondering is how happy we'll be with this solution as opposed to a pump fed recirc loop? If he achieves this warm trickle how stable will it remain through the seasons (Pacific NW)? Should I have any other concerns with this type of setup?

Anyway... just looking for thoughts. Thanks in advance.

The Plumber seems to be a very conscientious fellow who has done very nice work and has been a pleasure to work with so I'm not looking to slam him please.

**BacchusII** · 02-04-2006, 06:11 AM

I'm not sure I follow you completely but for what it's worth...
I installed a hot/cold water bypass valve to get low gravity flow between the hot & cold water line in a distant bath. The valve includes both a balancing valve and a check valve. The original one did not have the check ball and I did get some back flow - manufacturer indicated they had some get out incomplete and replaced it at no cost - worked fine after replacement.
See http://www.pumpsetc.com/aqualink.htm for info

Hope this helps

**Bob NH** · 02-04-2006, 06:29 AM

Gravity recirculation depends on having the vertical run of the hot water line hotter than the vertical run of the return line. One place I saw said that the last 15 ft of the return should not be insulated. They also said that if there is a check valve it should be a swing check and should have a hole in it between 1/8" and 1/4" to assure some flow.

You could have a problem with bypass if you have a hot water tempering valve. The flow resistance of that valve is greater than the flow resistance of the return pipe.

**Gary Swart** · 02-04-2006, 07:04 AM

I suppose you have a reason not to install a pump system, but that would solve your problem. You already have the return line, all that's needed is the pump.
This is the type I use, but there are others. http://www.lainginc.com/howhot.htm

**master plumber mark** · 02-04-2006, 08:13 AM

just try itand see what happens....

sometimes it works great and sometimes it dont..

it really depends on what the plumber bid the job to do....

I would prefer a gravity fed deal myself becasue you
eliminate a pump and you eliminate wear and tear on both
the pipes and the water heater...

I doubt is will draw off the botom of the water heater

I have seen these installed quite frequently and if it works its great...
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if it dont please you just install a pump with a timer...

its just a matter of who pays for it and what your plumber
said he would do in the bid....

hj · 02-04-2006, 08:51 AM

It is a question of flow resistance. If the path of hot water from the heater to that furthest point has more resistance than the more direct return line, then cold water will flow through it first, regardless of "balance". It is almost impossible to use a conventional valve, especially a gate valve if that is what he used, to adjust the flow for all the various situations that will develop over the course of a day's usage. A check valve installed a bit off level so the gate is ajar until backflow is attempted is the best way to achieve it. Actually, a pump system if the pump is always running would be the only one that MIGHT NOT need a check valve as long as the pump could maintain a positive pressure into the heater.

**neverman** · 02-04-2006, 05:50 PM

He for sure mentioned "path of least resistance" to ease concerns about mixing in the cold. Master Mark hit on several of the reasons we chose this avenue, plus I didn't wantto add another electrical outlet or deal with a pump in my facilities room. Simple is as simple does.

What kind of check valve stays open on a horizontal? This would be tough for us to do as the Heater is in a daylight basement and the return line comes straight down from the attic.

I believe it is a gate valve that was used... 90 degree on off lever type deal.

The only t in the system is at the closest point to our master shower. Farthest point away from heater by happenstance. We disin't want to wait forever for hot water, we didn't want a 2nd small water heater solution, we didn't want to go to the trouble of pumping the recirc when gravity was discussed as an option during the planning of the system early on. The Plumber stated he had great luck with his own gravity fed system and we decided to give it a shot as it cost nothing to implement. I did the return kinda on my off time.

Thanks again

**Bob NH** · 02-04-2006, 07:05 PM

You might be able to find a "ball check" which has a plastic ball in it, no spring. Install it in the return line where the back flow will close it; flow up if the ball sinks or flow down if the ball floats.

**BacchusII** · 02-04-2006, 07:36 PM

Check these out - they are simple and don't need any extra piping - simply install between hot & cold feed tubes on a sink... small needle balancing valve& ball check made for this application and they work! Eliminates need for pumps etc in most cases
See http://www.pumpsetc.com/aqualink.htm for info

**Bob NH** · 02-04-2006, 07:51 PM

I noticed that the Aqualink site has not a single word about the fact that you will get hot water coming out of your cold water faucets, even into the toilets, until you have used the water in the cold water line. You will probably get some additional hot water to your cold water taps via the parallel circuit that is your hot water line.

Maybe they have taken lessons from the computer software people; it's not a bug if you call it a feature.