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Author Topic: Water Heater Question  (Read 1057 times)

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Breakin Away

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Re: Water Heater Question
« Reply #30 on: November 14, 2019, 08:28:06 AM »

BA

I’ll submit that you’re using up too many brain cells over something that plumbers have figured out long ago.  :D 
The WH has a temperature & pressure relief valve set at 150 psi. The shark bite cv is 200 psi and if you use 1/2” copper stubs you can warm/expand the pvc water hose to fit over them.
If plumbers were doing it, I'd have all copper plumbing.

When Catalina did it, I ended up with a (apparently) hazardously under-spec'ed check valve. That's what's led to burning some brain cells over wondering whether the PVC ball valves in my manifold might also be under-spec'ed. I now see that the PVC ball valves I saw at Home Depot are spec'ed to 150 psi, so presumably the ones in the boat are similar.
« Last Edit: November 14, 2019, 09:58:50 AM by Breakin Away »
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2001 MkII Breakin' Away, #1535, TR/WK, M35BC, Mantus 35# (at Rock Hall Landing Marina)

Stu Jackson

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Re: Water Heater Question
« Reply #31 on: November 14, 2019, 09:23:26 AM »

I've had one of those "crappy" check valves in my water supply under the galley sink for 32 years on my boat, still works just fine.

I replaced the one under the head sink to the shower sump with an inline Raritan check valve.  The shower sump pump, IIRC, is in a different place on the Mark IIs. 

I posted pictures of the old and new years ago, I'll see if I can find it.
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KWKloeber

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Re: Water Heater Question
« Reply #32 on: November 14, 2019, 09:59:41 AM »


I've had one of those "crappy" check valves in my water supply under the galley sink for 32 years on my boat, still works just fine.


Ya, it’s presumably only an issue if the WH over pressures, and then (if I understand ShurFlo correctly) it could explode before the T&P safety valve releases.  The 100 psi cv will pop before the 150 psi T&P.

They’re not crappy, just not meant for the purpose it was installed, then doesn’t stand up when it’s needed.

Interestingly and related, new residential WH installations/replacements now require an in-line expansion tank to soak up the thermal expansion.
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Stu Jackson

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Re: Water Heater Question
« Reply #33 on: November 14, 2019, 11:00:31 AM »

I'm confused.  About the system pressure.  My domestic water pump is rated for X gpm at about, IIRC, anywhere from 40 to 55 psi.  The T&P safety release valve on the water heater appears to be there in case the heater itself has created over temp or over pressure.  But if the water system PUMP can only produce a max of say 55 psi, then what's the issue with the old check valve?  Sure, if the system clogs up and the pump keeps running, maybe, just maybe, that 55 psi could be exceed AT THE LOCATION of the check valve, but if that's ALL the pump can produce, where is that extra 100 psi coming from?
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KWKloeber

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Re: Water Heater Question
« Reply #34 on: November 14, 2019, 12:47:09 PM »

Stu

We’re talking about the cv on the cold water supply to the WH, which prevents backflow from the WH back into the cold water supply lines. It doesn’t see excessive pressure unless the WH goes heywire and over pressure (which the T&P safety valve would relieve.)  But that model ShurFlo cv is rated lower than the T&P, so it can explode before the T&P ever opens to relieve the pressure.
Per the email ShurFlo said they’ve “seen it happen” which is why they don’t approve that cv for a WH.
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Ron Hill

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Re: Water Heater Question
« Reply #35 on: November 14, 2019, 03:11:13 PM »

Guys : What Ken is talking about in the WH "back flow" prevention valve is "run-a-way" overheating when you are plugged into shore power!   :cry4`

A thought
« Last Edit: November 14, 2019, 03:16:09 PM by Ron Hill »
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KWKloeber

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Re: Water Heater Question
« Reply #36 on: November 14, 2019, 03:23:35 PM »

The check valve is checking whether the WH is on AC or heated by the engine. But of course it would explode ONLY if on AC - the engine wouldn’t get the WH hot enough to develop the pressure.
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Breakin Away

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Re: Water Heater Question
« Reply #37 on: November 14, 2019, 04:54:49 PM »

The density of water at 100°C is 4% lower than at 20°C. The water in a 6 gallon tank will expand by a quart in volume, putting pressure on hoses, barbs, valves, and pump. How much pressure depends on the elasticity and volume of those peripheral components, virtually all of which will be at ambient temperature because the water isn't flowing.

The density of water at 77°C (engine temperature) is 2.5% lower than at 20°C. The water in a 6 gallon tank will expand by 0.6 quart in volume. That's still significant expansion, and could test the limits of the check valve. Bursting is definitely less likely than using the electric heater, but not sure I'd say it's impossible.

What is the pressure rating of the heat-welded version of the check valve?
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Stu Jackson

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Re: Water Heater Question
« Reply #38 on: November 14, 2019, 05:02:46 PM »

Golly, I know exactly what check valve we're talking about.

One option is that if, as ba says, things start goin' south and pressure really builds, when the check valve goes, it could go along with the "...hoses, barbs, valves, and pump..."  IIRC, most pumps have check valves on the outlet, too. 

By then, one could/would have bigger issues than an old check valve.  Which on my boat has been working for 32 years. 

Of course there are better valves, and incremental improvements and enhancements are always welcomed.  I'm  just suggesting we put this in proportion.

Your boat, your choice.  :D
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Noah

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Re: Water Heater Question
« Reply #39 on: November 14, 2019, 05:10:48 PM »

Nothing like a heated discussion about hot water to get the pot boiling! 8)
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Breakin Away

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Re: Water Heater Question
« Reply #40 on: November 14, 2019, 05:12:39 PM »

I don't think that age of the check valve is a negative here. Ken said that the older ones bolted together and were pressure rated. At some point Shurflo changed the design to a heat-welded one. Not sure when that change was made, but your 32 year old one might be better than the newer ones. Does yours bolt together, and allow disassembly to clean the flapper?
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KWKloeber

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Re: Water Heater Question
« Reply #41 on: November 14, 2019, 06:01:55 PM »

BA

My '84 had the square, bolted version, and in 2005 I bought the new version for a different purpose.  When ShurFlo made the change - I dunno? 

I believe the current style cv is rated @ 100 psi.

Presumably, the fittings are rated at least as high as the T&P safety valve?   I dunno. 
The nylon barbed fittings I've used are rated 150 to 200 psi.

The cv rating is an issue only when it becomes an issue -- do we ignore a weak point?  I guess I just have a preventive attitude.  To me, my not addressing it and buying the metal cv -- would be like replacing a leaky T&P with a plug.  Hell, the T&P hasn't blown in all these years so why should I spend the extra money to replace it?  I only need a safety factor when I NEED it, and I can't predict when.  My luck is less than stellar but I wouldn't run out tomorrow and change the cv -- but why not add it to the to-do list just to have the additional insurance?
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Stu Jackson

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Re: Water Heater Question
« Reply #42 on: November 15, 2019, 04:37:23 PM »

I don't think that age of the check valve is a negative here. Ken said that the older ones bolted together and were pressure rated. At some point Shurflo changed the design to a heat-welded one. Not sure when that change was made, but your 32 year old one might be better than the newer ones. Does yours bolt together, and allow disassembly to clean the flapper?

Here's the pictures, should answer your question, too.

https://c34.org/bbs/index.php/topic,4114.msg33528.html#msg33528
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Re: Water Heater Question
« Reply #43 on: November 15, 2019, 05:26:05 PM »

That old bolt together ShurFlo was rated for WH use and was OEM on my ‘84.

Raritan specifically states re its RCV valve:
“Not for use on pressurized lines.”
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Noah

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Re: Water Heater Question
« Reply #44 on: November 15, 2019, 05:33:50 PM »

All of the check valves on my 1990 are the original bolt together ones and no issues (so far).
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