Need a low cracking pressure check valve

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groston

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In our house, we have a passive hot water recirculating system. It was worked for years, but recently the check valve in the line failed. Two comments: 1) This was a swing type check valve installed on a vertical piece of pipe connected to the output of the water heater and 2) We would, on occasion, see black particles coming from a hot water faucet. As an engineer, I simply don't understand why the valve was installed vertically as I suspect/fear that it never closed and the black particles were flowing up the reticulation line from the water heater.

I got a new swing-type check valve and installed it on a horizontal portion of the piping. While the reciculation function worked properly and the black particles mostly disappeared, regularly the valve would chatter (loudly and annoyingly) because water was trying to flow up the recirculation system when a faucet was opened. I asked about resolving this issue and was told to install a regular check valve.

I did some looking around and settled on a Swagelok B-8C4-1/3 because this valve has the lowest cracking pressure (rated at 1 psi) of any valve I could find. I installed it and 1) the noise went away but 2) the recirculation system may no longer be working (I suspect because there may not enough water pressure to open the valve).

I have two ideas for resolving this issue: 1) find a check valve with an even lower cracking pressure or 2) install the existing valve vertically. My ask of this group is simply this: Which approach should I follow? If replacing the valve, please recommend one.

Thanks.
 

JG plumbing

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I don't think this should be a problem. Could you draw the system with pipe sizes?
 

JG plumbing

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The path of least resistance should not be backwards. Your chattering valve shouldn't happen.
 

breplum

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There is no flow-pressure to open a check valve on a passive thermosiphon loop.
We never use check valves on passive loops that tie in to a tee at the the drain tap of the WH.
Not insulating the return portion of piping near the WH purportedly helps the system.
 

Mitchell-DIY-Guy

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I had a passive thermosiphon hot water recirculating system in my Michigan house for 27 years. Fully functional, always worked, zero maintenance. Supply lines ¾” to 2nd floor, ½” return line. Swing style check valve mounted horizontally (the only way to do it). Full-flow ½” shutoff mounted vertically. Return went to bottom of tank, with a PROPER full flow drain, not the crap plastic ones that simply don’t work today. Hot water heater in basement so there was a good “head” needed to make it work. Two story home. In operation it was absolutely completely silent. The return flow is very low flow and no pressure.

You need a good head and that swing check to make it work. The black particles? Nothing to do with recirculating; something else going on.

The plumber for my builder put it in in 1992, and I silently thanked him every day for the 27 years we owned the home. Neighbors with different builders complained of long waits for hot water.

Here in NC I couldn’t convince the plumber that it would work and they scoured the local codes to find reasons NOT to do it. But this is a place where they put water heaters in the attic (or use electric when natural gas is available) because they haven’t figured out how to vent a gas heater cheaply. Basements are exceedingly rare. They like putting crawl spaces in to annoy the trades, grow mold, and attract bugs and snakes. 😉
 

groston

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Mitchell: Thanks. Our passive thermosiphon system has worked until the vertically mounted swing style check valve failed. The black particles, which have been present since day one, are coming from the water heater via the recirculation line (as the recirc line attaches to the bottom of the tank). Our return line is a 1/2” and I am not sure if the supply line is 3/4” or 1/2”.

The issue is that when I replaced the swing check valve and mounted it horizontally, most of the time when a hot water faucet was opened, it chattered very loudly. Thus my query.

breplum: As noted, we need a valve to block the flow of water to the faucets from the recirc line. Also, the recirc line is not insulated.
 

Mitchell-DIY-Guy

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A failure on a swing check valve? Did the flapper break off or something? That's exceedingly rare. I had the same valve for 27 years, no noise ever, no failures.
Any kind of spring check valve has parts that wear out; springs and seals. They will certainly fail over time. @breplum points out there's no pressure in which to crack a spring check.
Is it possible that there were (thanks to @Twowaxhack for pointing it out) small hole(s) drilled into the original flapper on the now broken valve?
You are in Michigan so this is in a basement, and the return line starts on 2nd floor...so you should have plenty of head.
Have you tried re-plumbing it in the way it was? If that worked for you, you should go back to it.
There's a TON of information on passive thermosiphon systems out there...but if you had a system that worked go back to what you had, just with a new working valve in the same location.

You also indicated that we need a valve to block the flow of water to the faucets from the recirc line. In my system, the return line was the return line; nothing attached to it. It made a direct beeline from the second floor down to the water heater. The fixtures and faucets were fed off the supply lines.

Nearly all the homes/apartments in the Middle East feature these these systems, though for hot water generation not recirculation but the thermodynamics are identical. There, these are roof mounted, two solar collectors, and a highly insulated storage tank. No pumps.
 

JG plumbing

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A failure on a swing check valve? Did the flapper break off or something? That's exceedingly rare. I had the same valve for 27 years, no noise ever, no failures.
Any kind of spring check valve has parts that wear out; springs and seals. They will certainly fail over time. @breplum points out there's no pressure in which to crack a spring check.
Is it possible that there were (thanks to @Twowaxhack for pointing it out) small hole(s) drilled into the original flapper on the now broken valve?
You are in Michigan so this is in a basement, and the return line starts on 2nd floor...so you should have plenty of head.
Have you tried re-plumbing it in the way it was? If that worked for you, you should go back to it.
There's a TON of information on passive thermosiphon systems out there...but if you had a system that worked go back to what you had, just with a new working valve in the same location.

You also indicated that we need a valve to block the flow of water to the faucets from the recirc line. In my system, the return line was the return line; nothing attached to it. It made a direct beeline from the second floor down to the water heater. The fixtures and faucets were fed off the supply lines.

Nearly all the homes/apartments in the Middle East feature these these systems, though for hot water generation not recirculation but the thermodynamics are identical. There, these are roof mounted, two solar collectors, and a highly insulated storage tank. No pumps.
Is sling check was vertical that's incorrect
 

Mitchell-DIY-Guy

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It didn't. It washed black particles into his fixtures.
Yes, the recirculation system worked, as he said...until the check valve broke. He should simply replace the check valve with exactly what was there, in the same location. Do it the same way it was done when it worked, with the same check If the gate had holes drilled in it, then he needs to do that too. Simple.

I agree with you, @JG plumbing that any swing needs to be horizontal. Mine was. Along with others I've used. But I'm also not dismissing the OP that he had a working recirculation system.

The black particles have nothing to do with the recirculation system. Find the source, clean it up. Drain/flush the HWH? Bad gaskets/seats/seals on faucets? Maybe just debris coming in? Who knows. I cannot speak for him, but it sounded like he had a working system until his CV broke. He replaced it, and moved it, and now the system doesn't work. His original thought was to use a low cracking pressure spring check, but that won't work since there's no pressure on the return. If debris is a problem, use a WYE strainer, one you can isolate with valves so you can clean it. My system didn't "wash back" anything since the flow was ONLY one direction, from the 2nd floor to the bottom of the tank. Water for the fixtures came from the supply lines, not the recirculation line. I'm sure the bottom of my various hot water heaters (three in 27 years) held all kinds of debris. No system is perfect.
 

JG plumbing

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Dude your wrong. It was installed incorrectly and reverse flowed through his system.
 

JG plumbing

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Your whole "put it back wrong and malfunctioning" way of thinking about this, is why this method is no longer legal.
 

groston

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I agree that a swing-type check valve should not be installed vertically. The black particles are coming from the water heater (which has been flushed). Since the valve was installed vertically, I doubt that the valve ever closed, thus water flowed from the heater to the faucets via the recirculation line (which exits the water heater from the bottom).

When I installed a swing-type check valve horizontally, it chattered loudly, which is why I replaced it with a spring-type check valve, but there is insufficient head to open the valve, thus the recirculation system is not working.

In answer to JG Plumbing: Yes, the flapper simply broke off. As was suggested, the chattering might be eliminated by drilling a hole in the flapper. (And yes, I do have a new swing-type check valve to do this to.) Does this seem like a good solution (as it is easy to do)?

Thanks all for your thoughts!
 

JG plumbing

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I've not tried this solution in this application with these type of perameters. I'm not sure how this would stop reverse flow, but if you'd like to try it's a free country.
 

Mitchell-DIY-Guy

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Listen—there’s a LOT of diagrams and information on this extremely simple setup, in a variety of different places. Just follow them. In brief summary: dedicated return line (NOTHING attached to it); horizontal swing check. Shutoff valve to disable flow. Full flow drain at tank. Want to get fancy? Use unions so you can easily change the check. Concerned about floaters? Use a WYE screen. The check must be mounted with the flap hinged at top…follow directions.

Unlike most who TALK about it here, I had it installed and working for 27 years and lived with it. Flawless. Silent. No maintenance.

I moved from Michigan. Fast forward to trying to build a new home in NC. I had an extremely difficult time (not sure I did) convincing one of the largest plumbing operations in the Carolinas that this would work. They never heard of such a thing, wanted me to buy a Watts pump instead! They insisted that the return line be fully insulated which interferes with the temperature differential needed to make passive thermosiphon work. On this new build, for which they did all tough and finish work, their answer was to charge an additional $1,500 to run the 75’ of ½” PEX needed for the return line, with no guarantees. I gave up. No fixing that mindset.

Best of luck! If you follow the instructions, it will work. If not your home violates the laws of thermodynamics.
 

JG plumbing

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Listen—there’s a LOT of diagrams and information on this extremely simple setup, in a variety of different places. Just follow them. In brief summary: dedicated return line (NOTHING attached to it); horizontal swing check. Shutoff valve to disable flow. Full flow drain at tank. Want to get fancy? Use unions so you can easily change the check. Concerned about floaters? Use a WYE screen. The check must be mounted with the flap hinged at top…follow directions.

Unlike most who TALK about it here, I had it installed and working for 27 years and lived with it. Flawless. Silent. No maintenance.

I moved from Michigan. Fast forward to trying to build a new home in NC. I had an extremely difficult time (not sure I did) convincing one of the largest plumbing operations in the Carolinas that this would work. They never heard of such a thing, wanted me to buy a Watts pump instead! They insisted that the return line be fully insulated which interferes with the temperature differential needed to make passive thermosiphon work. On this new build, for which they did all tough and finish work, their answer was to charge an additional $1,500 to run the 75’ of ½” PEX needed for the return line, with no guarantees. I gave up. No fixing that mindset.

Best of luck! If you follow the instructions, it will work. If not your home violates the laws of thermodynamics.
You realize I have two of these systems going right now and a true thermosyphon (which is a seperate thing). Three systems. No talk. A hole in the check valve doesn't do what we want which is both circulation and leaving particles in the tank where they can be ran out during cleanings.

When you open a faucet in a true gravity system the water that isn't being drained from the system should circulate. This means that a chattering check valve is installed on an incorrectly designed system. Which were trying to work through here. Your amateur opinion is welcome, but don't pretend you have some insight on this just becuse you had a system. There are things that happen that you may not have thought of. Which also includes me. I haven't thought of everything which is why the forum exists.
 

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