Indirect hot water heater relief valve opened.

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PaulYM

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Hello. I have a Top Performer Plus by Vaughn, model: S50TPPB. It has a 150psi 210 degree relief valve.

I have an Alpine Condensate boiler running a zone to it. A few years back every once in a while the relief valve on the water heater would slightly lift and then close only during heating up. I was told to put an expansion tank on the cold water feed right before it enters the tank. Problem solved. A few years later, its doing the same thing for the past couple of months, but seems like the valve lifts more often, but still only when being heated. Tonight i took a shower and sat down to eat dinner and i thought a pipe burst in the basement. I go down and the relief valve is all the way open and water everywhere. I closed the main water supply valve, then closed the relief valve. Again, this is while heating.

Now im terrified to even leave the water on tomorrow while im not home. Thank god i was home. The relief valve was wide open and it didnt seem like it would close on its own because the lift handle was all the way open. What is going on with this thing? What should I do? Im almost tempted to pipe the relief into the sewer in case this happens again because I dont trust it.

I know the relief valve is doing what it is supposed to, but why now, why a little bit, a little bit for months, and then BAM!!!!? Ok im done crying lol.

Thanks
 

WorthFlorida

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You need to check the expansion tank. Probably the bladder inside the tank has burst and it was full of water, therefore no room for expansion. There are plenty of YouTube videos on how to setup and check an expansion tank. You alway need to check the pressure on an expansion tank about once or twice a year just this this reason.

Depending where you are in NY, the cold water inlet is very cold and it needs a lot of room for expansion when heated. My home in Saratoga the pressure valve would open occasionally, fortunately the pipe from the valve went through the outside wall to the ground. My 3rd home in the Syracuse area the inlet temperature had to be around 40 degrees. It is always a good idea to bring the drain pipe to a sump pump. If you want to connect it to a sewer drain, you must set up with an air gap, like a washing machine standpipe. It is important that no one can be splashed by scalding hot water. In you situation it is most likely a pressure build up. This time is sounded like a burst because the valve may have stuck closed from some rust or minerals. Occasionally the T&P valve should be opened and flushed for a few seconds. You'll may see some rust and sometimes they are a bear to open.

Get a pressure gauge to get an idea on the pressure you are dealing with. You can place it on the washing machine connection or an outside spigot. It has a red needle that is a tattle tail. It will be moved up the scale by the black needle and stay at the highest position.

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jadnashua

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I’m due east of Syracuse (about 300-miles!), and I’ve personally measured my incoming cold water at 33-degrees after a long cold spell...

If you tap on the expansion tank, it will probably sound with a dull thud. If you take a tire pressure gauge and check, you’ll probably get some water out...both a sure signs the tank is shot. If you don’t get water out when checking the pressure, you might be able to just add some air, but the procedure for that requires you shut the water off, open a valve to relieve pressure and then you can pressurize the tank again to see if that solves your problem, otherwise, it’s replace the tank.
 

PaulYM

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Thanks for the advice guys. I was thinking maybe just put one of those guages on the tank itself and leave it stationary. If I do it this way, should I put it on the cold water feed-in or the hot water feed-out? Or maybe both sides? And should i put above expansion or below? Thanks
 

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Bannerman

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should I put it on the cold water feed-in or the hot water feed-out?
The pressure on both should be virtually identical. Installing a guage on the incoming cold line should be sufficient.

Cold water will expand when heated. The large amount of hot water used while showering will have resulted in an equivalent quantity of cold water entering the WH. Water cannot be compressed so if there is nowhere for the expansion to be absorbed, then the WH's Thermal Pressure Relief valve will open to relieve the excess pressure.

As stated, if the rubber diagphram within the existing thermal expansion tank has ruptured, then the tank will be waterlogged so there will be nowhere remaining for expansion to be absorbed.

Shut off the cold water supply valve to the WH and open a hot faucet to relieve the pressure. Once there is 0 pressure to the hot faucet, then the thermal expansion tank should contain 0 water. If the tank continues to contain water, then the diagphram is likely torn and so the tank will need to be replaced.

Since you said there was a large volume of water flowing from the TPR valve, it seems as though if was releiving more than just excess pressure. What temp is the WH thermostat set for? Perhaps the thermostat was stuck so the water temp exceeded 210F? Alternately, maybe the TP valve once opened, became stuck open and continued to dump water even after the pressure was reduced?
 
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jadnashua

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The T&P valves are safety devices that aren’t really designed for regular use...if they are required to open frequently, after you figure out why and fix it, you may find you need to replace the T&P valve, too. They can get sticky from mineral deposits if they’re called on to open frequently, and that can prevent the stem from allowing it to reseat properly. And, while open, it’s possible to get some crud stuck on the mating surface that can allow it to weep. Sometimes, opening it fully momentarily will allow it it flush out that crud, but not always. If that doesn’t work, it’s replacement time.

Your ET is probably shot. Fix that, and then see if there’s anything else required.

When using a pressure gauge, look for one that has a tattle tale hand that will show peak pressure...if the ET is sized and setup properly, the pressure should be almost constant, only very slightly rising after a water heating cycle and then immediately dropping once you open a hot water valve so the bladder can rexcpand from its compression due to the expansion.
 
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for reference 25 gallons of water entering the WH at 40°F takes up 25 gallons of space. Once it's heated to 140°F it takes up 25.43 gallons.

Sounds like the the expansion tank is shot. When replacing the expansion tank it's probably a good idea to replace the relief valve too.
 

PaulYM

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I’m due east of Syracuse (about 300-miles!), and I’ve personally measured my incoming cold water at 33-degrees after a long cold spell...

If you tap on the expansion tank, it will probably sound with a dull thud. If you take a tire pressure gauge and check, you’ll probably get some water out...both a sure signs the tank is shot. If you don’t get water out when checking the pressure, you might be able to just add some air, but the procedure for that requires you shut the water off, open a valve to relieve pressure and then you can pressurize the tank again to see if that solves your problem, otherwise, it’s replace the tank.

Ok, the tank sounds full with water when I tap it, but when i pushed the air valve, no water comes out. How many LBS should I pump it up?
 

WorthFlorida

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Needs to be about your average daily pressure. This video explains it. Most homes fall above 50 PSI. 60 PSI is more ideal but it could be higher. Some tanks are set up reverse. water connection is on top. It makes no difference.

 

jadnashua

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Just like a tire, the valve on the ET can slowly leak. If no water comes out of the fill valve, the bladder has probably not failed. You need to know your static water pressure, then shut off the water, open a valve, and pressurize the tank to that value.
 

PaulYM

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Ok, so I finally got the pressure guage in the mail. My water pressure is 80Lbs. I pumped the expansion tank up to 80Lbs and now it actually has a ping noise on the air side when I flick with my nail. Cool. I'm thinking this is solved as long as i dont see any water come out of the relief during heating. Thanks guys.

Just for future, is there a particular size tank that should be on the water heater? The one on my boiler looks twice the size as the one on my water heater.
 

Bannerman

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My water pressure is 80Lbs.
80 psi is the upper limit for residential plumbing. As it seems your water supply is municipal, add a pressure regulator valve where the water supply enters your home so as to lower the incoming pressure. Many municipal systems deliver 60 psi which is sufficient for most applications.
 

jadnashua

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While it doesn’t hurt to use an oversized ET, yes, there is a problem if it is undersized for the intended application. If you go to any one of the websites of companies that make ETs, they generally have a calculator on there to help you decide what size you need. You will need to know three things:
- how big the WH is
- the setting on the WH
- how cold your incoming water is (use the wintertime value)

Depending on the type of heating system you have, your boiler still needs the same information to decide how big of a tank it needs. Because the temperature extremes can be larger with a boiler, it’s not unusual for the tank size to be larger, but it all depends on the system as some run on a fairly small volume of water while others could use more than a typical WH.
 
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