Leaking Pressure Relief, or 'blow-off', valve


  #1  
Old 06-07-10, 09:38 PM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
Leaking Pressure Relief, or 'blow-off', valve

Hello everyone, I stumbled upon this website and hopefully I can get some advice. I live in a townhouse with a partially finished basement. In the unfinished side of my basement I have one area where the gas hot water heater is under my stairwell, and in another area I have a washer/dryer/storage area, etc. Next to my washing machine hookups is a pressure relief valve.

When i moved into the house in early April, it was 'blowing off' once every hour or so. Then it became a steady drip until it was almost 2-3 drips per second coming out of the valve. I had a plumber come out and look at it, he replaced the valve. He said it is a 75psi valve which releases water pressure if the pressure in my lines gets that high. At the time, he took a measurement at cold water line to the washing machine and it was around 55psi.

It has been two weeks now, and the valve is doing the same thing, dripping almost constantly for a few hours at a time, or unless I turn something such as a faucet on, which I assume releases the pressure in the lines. I called the same plumber who came out for free to check on his work; he adjusted the valve and said it was fine and was working like it was supposed to...

For some reason I feel antsy about this and just want to make sure it is ok! Like I said, it seems like the pressure in my line is building up and dripping constantly through the pressure relief valve. Eventually it stops on its own, or I can make it stop for a few hours by opening a faucet/flushing a toilet, etc.

Sorry for the long post, any advice? Thanks in advance.
 
  #2  
Old 06-07-10, 10:12 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 37 Likes on 29 Posts
My first thought is that you have a "closed" water system and after using enough hot water to get the heater to fire the pressure is rising because of thermal expansion. Sometimes a relatively low set pressure is used on a safety relief valve to prevent this thermal expansion from becoming a high pressure situation. The more modern thought is to incorporate an "expansion tank" in the cold water piping to the water heater to allow for this expansion.

A closed system is made when there is a check (one-way) valve in the water supply from the municipal utility OR a pressure reducing valve (PRV) is installed to lower a high utility pressure to a more appropriate household pressure. Sometimes the utility's meter will have a check valve built in and when such meters are used to replace an older meter the problem will arise.

Post back if you want information on installing your own expansion tank.
 
  #3  
Old 06-08-10, 07:14 AM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
Thanks a lot for the info. I would have assumed that an expansion tank would have been installed already...the house was built in 2003 so its not old at all.

I'll look into the expansion tanks.
 
  #4  
Old 06-08-10, 12:55 PM
shacko's Avatar
Member
Join Date: Aug 2005
Location: Baltimore County Maryland
Posts: 2,137
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by terpnorth View Post
Thanks a lot for the info. I would have assumed that an expansion tank would have been installed already...the house was built in 2003 so its not old at all.

I'll look into the expansion tanks.
You know what happens when you assume

There are a lot of areas that require an expansion tank on ALL water heaters, some only require them when your incomming pressure is over 80psi and you install a PRV you need one because you created a closed system.

If you have one it should be a small tank on or near your water heater
 
  #5  
Old 06-13-10, 12:21 AM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
So I looked around my water heater...no signs of said expansion tank. I also put a pressure gauge on the valve where my cold water line connects to my washing machine. When water is running, the pressure is around 40 psi. As soon as the faucet is closed, the pressure steadily rises to 75 psi, at which point the water starts dripping out of the PRV.

Just wondering...is the pressure increasing because of the hot water heater? Would an expansion tank prevent this dripping out of the PRV? It usually drips for 30 min or so, and then stops and settles around 60 psi for a few hours, and then starts back up again. Why is it dripping instead of 'blowing off'?

Sorry for all the questions, hopefully someone has some answers!
 
  #6  
Old 06-13-10, 11:54 AM
shacko's Avatar
Member
Join Date: Aug 2005
Location: Baltimore County Maryland
Posts: 2,137
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by terpnorth View Post
So I looked around my water heater...no signs of said expansion tank. I also put a pressure gauge on the valve where my cold water line connects to my washing machine. When water is running, the pressure is around 40 psi. As soon as the faucet is closed, the pressure steadily rises to 75 psi, at which point the water starts dripping out of the PRV.

Just wondering...is the pressure increasing because of the hot water heater? Would an expansion tank prevent this dripping out of the PRV? It usually drips for 30 min or so, and then stops and settles around 60 psi for a few hours, and then starts back up again. Why is it dripping instead of 'blowing off'?

Sorry for all the questions, hopefully someone has some answers!
Are you talking about a PRESSURE (RELIEF) VALVE or a PRESSURE (REDUCING) VALVE, one is for relieving pressure only, the other is for reducing the incomming pressure.

A presure relief valve will start dripping when your incomming pressure goes beyond the rating on the valve; could happen any time of the day or night.

A pressure reducing valve throttles the pressure down to a reasonable number that won't harm your system. Pressure Reducing Valves need to be installed in conjunction with a expansion tank on your water heater to stop the release of water out of the T+P valve (on the water heater) due to thermal expansion when the heater fires.

If you have a pressure (RELIEF) valve only, that needs to be removed and an expansion tank installed at the water heater.
 
  #7  
Old 06-13-10, 05:59 PM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
Thanks...it is a Pressure Relief Valve...so it looks like an expansion tank needs to be installed next.
 
  #8  
Old 06-13-10, 09:38 PM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
So one final question....

If an expansion tank is required due to some codes, are there any reasons why one wouldn't have been installed when my water heater was put in 5 years ago?

I assume an expansion tank would keep the water in the lines, whereas the pressure relief valve just dumps the water down the drain, so to speak.
 
  #9  
Old 06-14-10, 02:04 PM
shacko's Avatar
Member
Join Date: Aug 2005
Location: Baltimore County Maryland
Posts: 2,137
Likes: 0
Received 0 Likes on 0 Posts
I think I answered this question on a previous post.

>>>If an expansion tank is required due to some codes, are there any reasons why one wouldn't have been installed when my water heater was put in 5 years ago?>>I assume an expansion tank would keep the water in the lines, whereas the pressure relief valve just dumps the water down the drain, so to speak.
 
  #10  
Old 06-14-10, 06:37 PM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
Thank you! Just wanted to make sure I fully understood all of the components involved.
 
  #11  
Old 06-20-10, 01:51 PM
P
Member
Join Date: Jun 2010
Location: usa
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
[QUOTE=shacko;1737586]I think I answered this question on a previous post.

>>>If an expansion tank is required due to some codes, are there any reasons why one wouldn't have been installed when my water heater was put in 5 years ago?>>I assume an expansion tank would keep the water in the lines, whereas the pressure relief valve just dumps the water down the drain, so to speak.
 
  #12  
Old 06-20-10, 03:49 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 37 Likes on 29 Posts
Plumbetter, several years ago it was customary to install a pressure-only relief valve in the cold water supply to a water heater IN ADDITION to the required T&P relief valve mounted on the heater itself. This additional relief valve would have a set pressure slightly more than the nominal municipal water pressure and was for the sole purpose of relieving excess pressure created by heating the water. The instructions given to replace this additional relief valve with an expansion tank is absolutely correct.

If you didn't know this little fact then perhaps your plumbing education is somewhat lacking in how certain things were done years ago.
 
  #13  
Old 06-20-10, 04:52 PM
P
Member
Join Date: Jun 2010
Location: usa
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
My bad. I got excited when I thought somebody was about to plug off a leaking T&P. Sorry.
 
  #14  
Old 06-20-10, 05:00 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 37 Likes on 29 Posts
Completely understandable and I apologize if I came across too strongly.

I think that people that plug T&P valves should be shot. We had an incident of that happening a few years back in a strip mall south of Seattle. It was "only temporary" but the water heater blasted a dry cleaner and some other shop while landing a few hundred feet from its original position. Luckily no one was hurt but...
 
  #15  
Old 06-21-10, 01:18 PM
shacko's Avatar
Member
Join Date: Aug 2005
Location: Baltimore County Maryland
Posts: 2,137
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by furd View Post
Completely understandable and I apologize if I came across too strongly.

I think that people that plug T&P valves should be shot. We had an incident of that happening a few years back in a strip mall south of Seattle. It was "only temporary" but the water heater blasted a dry cleaner and some other shop while landing a few hundred feet from its original position. Luckily no one was hurt but...
Thanks for the defense Furd.

I don't know if you seen where someone a while back plugged the T+P valve on a water heater, heater blew and went the roof of the house with enough force to blow the house off its foundation and land through the roof of a house 600 ft. away.
 
  #16  
Old 07-11-10, 02:26 AM
steve_gro's Avatar
Member
Join Date: Jan 2004
Location: San Francisco
Posts: 1,092
Likes: 0
Received 1 Like on 1 Post
Furd nailed it right off the bat - install an expansion tank near the cold inlet of the water heater. Not expensive & not difficult.

Here's what can happen when you plug a TPR:

Water Heater Blast!
 
  #17  
Old 10-08-10, 09:21 AM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
Hey everyone...it's been a while since I started this thread...I've been out of town for work a lot and just got around to installing an expansion tank.

I selected a Watts tank based on water heater size, etc., and installed this week...cold water line, close to the water heater, no issues.

When I first posted, water was 'blowing off' through the Pressure Relief Valve (NOT the T&P valve on the tank), however over the last few months it became a steady stream of drips and would only stop when I had a faucet/shower on to relieve the pressure in the line...when I would turn a water source off, the pressure would spike back up within 10-15 minutes and would begin coming through the relief valve.

I left the PRV installed after I installed the Expansion Tank, just to have the satisfaction of hearing no more drips...........this was not the case.

About two hours after turning the water and heater back on, the expansion tank apparently filled the water pressure in the lines (checked with a gauge on the cold line) came up to ~75psi (the valve is set to yield at 75psi) and began dripping through the valve again.

Not sure why this is happening, and I'm a little hesitant to delete the PRV from my system if the pressure is still doing this. Not sure if it matters, but I felt the cold line which comes into the water heater, and it is warm to the touch.

Any advice would be appreciated.
 
  #18  
Old 10-08-10, 10:26 AM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 21,110
Received 5 Likes on 5 Posts
You need to probably install a Pressure Reducing/Regulating Valve....75PSI is pretty high for a home. If it runs that way consistantly, you could get spikes over 100 when work is done on the system, assuming you are on municipal water.

If you already have a PRV (not relief valve)...it's either set too high or malfunctioning. I saw it was mentioned a couple of times...but it was never clear if you have one or not.
 
  #19  
Old 10-08-10, 10:32 AM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
I currently have a gauge hooked up to the cold line. When a faucet or some water using device is run, the pressure lowers to a constant 40psi, but as soon as it is turned off the pressure steadily increases. It stops once it gets to the Expansion Tank's pressure (50 psi is what I set it to), and after the tank fills (I think this is what happens), the pressure increases to 75psi, which is what the Pressure Relief Valve (again, not the T&P valve, the valve hooked to my cold line which is supposed to 'blow-off') is set too. At this point dripping ensues...

Sorry if that wasn't clear.
 
  #20  
Old 10-08-10, 12:16 PM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 21,110
Received 5 Likes on 5 Posts
Expansion tanks never really empty or fill after install (well..not completely I don't think)...the level will fluctuate to some extent as pressures equalize.

Your info really would have me looking for a PRV (regulator) somewhere that isn't working correctly.

Whats the time frame for all your readings? Does it do these things even when the water heater isn't firing?
 
  #21  
Old 10-08-10, 12:55 PM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
Thanks for your response.

This happens 24/7. At first when I moved in (april 2010) the Pressure relief valve would blow off, like it was supposed to. The valve started dripping and I replaced it. The new one dripped, and eventually it got to the point where it was dripping constantly (24/7) unless I had a the water on (shower, toilet, etc). This is the point that I started this thread, and installed an expansion tank as was recommended.

Like I said, the pressure when using the water (sink, etc) is a steady 40 psi, and I can bump that up or down a few psi by adjusting the bolt on the valve near my water inlet in the basement. I just don't understand why the water pressure increases so quickly...even when the heater is not firing. I understand that water expands, yada yada, and that when the water heater heats the water, some of it may back up into the cold line, resulting in increased pressures...but shouldn't the expansion tank catch all of that?

And yes, it happens even when the water heater is not firing.
 
  #22  
Old 10-08-10, 01:02 PM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 21,110
Received 5 Likes on 5 Posts
AHA!!!!! We found the issue! That valve in the basement is your regulating valve! Replace it and your problem is solved!

Sometimes it takes a different view (even by a non pro) to see the forest.
 
  #23  
Old 10-08-10, 01:07 PM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 21,110
Received 5 Likes on 5 Posts
I forgot to add....regulating valves have ranges that they cover. It's possible that the city system is exceeding that range.

I may have missed it...where are you located?
 
  #24  
Old 10-08-10, 01:29 PM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
I am in Harford County, MD.

So the regulating valve you are talking about...is this my pressure relief valve (the blow-off valve), or is this the valve that I can adjust the bolt on to alter the water pressure?

I still don't understand how the water pressure increases so quickly? Sorry if i'm missing the obvious point here...I'm no plumber.
 
  #25  
Old 10-08-10, 01:39 PM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 21,110
Received 5 Likes on 5 Posts
The regulating valve is the one in the basement with the bolt. It was mentioned way back in the earlier posts. I think it just got glossed over when the discussion went to why your relief valve was there w/o an expansion tank.

Try this just as a check...hook up your gauge to an outside spigot (hose thread gauge I hope?) and see how pressure changes. Many installs have outside spigots BEFORE the PRV (regulating).

It's very common for regulating valves to function fine as long as there is flow..but once the system is closed they leak by and allow full pressure. You might be able to rebuild it..but they aren't that expensive and are pretty simple to replace.

I'm still of the opinion that if there hadn't been the complication of the relief valve installed, you'd have had an answer in the first few posts.
 
  #26  
Old 10-08-10, 02:26 PM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
Thanks for all the input.

Unfortunately I can't check that...my hose (both of them) are plumbed in AFTER the Pressure Regulating Valve.

This makes the most sense, especially now that the expansion tank is there. I will do some research on replacing these valves. Looks pretty simple.

I didn't even think it could be something like that, since the water pressure when a faucet is on is good (40 or so), and then jacks up so high so fast when the faucet is closed.
 
  #27  
Old 10-15-10, 08:42 PM
T
Member
Thread Starter
Join Date: Jun 2010
Location: USA
Posts: 25
Likes: 0
Received 0 Likes on 0 Posts
Just wanted to give an update...I replaced the pressure regulating valve, and all issues are fixed! Thanks to everyone who provided some input, it was a learning experience for me.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: