How do you do that?
Water heater discharging through relief valve
- Thread starter Foster Nordic
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How do you do that?
Delfin
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Because Marine water systems all rely on an on board pump for pressure (if not connected to shore water), I believe you'll find that check valves are a mandatory component of every pump to avoid bleeding pressure back into the storage tank, and can't/shouldn't be fiddled with. A hot water rated expansion tank on the output side of the water heater, or a cold temp rated tank on the inlet side makes living with pressure/temp relief valves a bit easier.
Maerin
Guru
No, the check valve in the pump prevents pressurized water flow back into the storage tank/suction line. Without an inlet check, the pump would constantly cycle. The check on the water heater cold inlet is solely to prevent backflow of heated water into the cold piping. Creating a bleed path WILL NOT defeat its intended purpose, nor will it have any detrimental effect otherwise. I would not suggest doing it if that were the case.
Delfin
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I believe that is exactly what I wrote. Quoth I..."I believe you'll find that check valves are a mandatory component of every pump to avoid bleeding pressure back into the storage tank, and can't/shouldn't be fiddled with."
Your recommendation that you drill holes in a check valve associated with the water heater kind of begs the question of how that accomplishes anything if the check valve in the pump is preventing a backflow of water through the cold water line? Further, I probably missed it, but water heaters don't come with check valves in the first place, although they can certainly be installed. Once installed, any cold water expansion tank might be isolated, which is why a rated hot water expansion tank on the hot water side is the preferred solution. https://www.plumbingsupplynow.com/plumbing/expansion-tanks/extrol/ex-30-extrol-inline-boiler-system-expansion-tank-4-4-gal-ex-30?utm_source=bing&utm_medium=cpc&utm_campaign=**LP%20Bing%20Shopping%20All%20Products&utm_term=4574861726366155&utm_content=Catch%20All
To make it a bit more muddy, some folks confusingly refer to the TP relief valve as a check valve. Go figure. https://www.reference.com/home-garden/check-valve-water-heater-ed922c7880e2a195
And for what it's worth, plumbers on hot water check valves....https://www.plbg.com/forum/read.php?1,231398
Maerin
Guru
Says the manufacturer who's in the business of selling T&P valves.
It also has the collateral benefit of reducing their liability exposure. As a service provider, inspection was our SOP, any evidence of prior leakage would be cause to recommend replacement of the T&P. Active leakage was a "must replace" and any plugged device would be a replace, period. If I saw a plugged relief in the course of a site visit, I would correct it or tag out/lock out, even if I was not paid for the service; then document it & have the homeowner sign off if they declined a repair. As a professional, I could be held liable for not correcting a life safety issue like that or in the instance of a heating appliance that's producing CO. "Testing" a T&P was never on our task list- inspect or replace!
Maerin
Guru
Evidently, I didn't make my point clearly. I did refer to the check on the water heater, its sole purpose is to prevent hot water from backing into the cold supply. It's independent of the pump and has no function in preventing the pressurized water from backing into the suction line of the pump or the storage tank. That is the function of the check on the pump, and without it the pump will cycle. Two different check valves, two entirely different functions. What did I miss?
The link you provided is for an Extrol EX-30. It's a thermal expansion tank designed for use in hydronic systems, not potable water. Entirely different tank than the thermal expansion tanks for use on pressure water systems (ST series). The Extrol 30 will tolerate 190F water in use on a hydronic system, but pressures there are <15psi. And it's a closed system, so the water in that system is inert for all intents and purposes. The EX-30 wouldn't last on a water heater application; that's simply not what it's designed for.
The preferred solution for a water heater application is a thermal expansion (ST) tank on the cold side of the supply piping. Providing a bleed path through the water heater inlet check allows a de minimus flow of thermal expansion back through the water heater inlet check and thus to the piping that the thermal expansion tank is connected to. Not enough to heat the line, but enough to allow installation of the ST tank anywhere on the cold side where it is preferred and will last the longest. It won't have any bearing on the pump check valve.
Regarding the link to whatever idiot wrote the drivel on check valves on water heaters being a safety device, it IS the internet. That makes it true, not??
Similarly, the link about check valves written by the apprentice is a common question. A residential heater may have heat trap valves from the manufacturer, but the dip tube configuration is typically enough to keep the contents from backing into the cold supply line. Because marine heaters are more often than not piped with side inlet/outlet, there's little to prevent flow of hot water or thermal convection into the cold supply piping, so a check valve is frequently installed for that purpose. I doesn't have to seal perfectly to achieve that purpose.
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Delfin
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I gather you must be suggesting that a check valve be installed to prevent thermal transfer of heat from the hot water side to the cold water side, since an actual flow of water from hot to cold is prevented by the check valves in the water supply pump. One would think a heat trap might be more efficient, but ok. Once you drill holes in the check valve it seems like you are pretty much defeating the purpose, but again, ok.
Quite right. I had that model on the brain since I just installed one in my hydronic system. That said, most all potable water expansion tanks I've seen are all rated for 150 psi and 200 degrees anyway and are protected by the TP relief valve, so if you do feel compelled to install a check valve, rather than drilling holes in it, installing the tank on the hot water side would seem to make sense.
True. Until you install a likely unneeded check valve (on a closed marine system) that would prevent it from working.
True enough. There is sufficient bad advice on the Internet to go around.Regarding the link to whatever idiot wrote the drivel on check valves on water heaters being a safety device, it IS the internet. That makes it true, not??
