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-   -   leaking pressure relief valve on heating water boiler (http://www.diychatroom.com/f17/leaking-pressure-relief-valve-heating-water-boiler-32959/)

benjamintr 12-01-2008 02:05 PM

leaking pressure relief valve on heating water boiler
 
One of my hot water radiators had been leaking around the valve. When the repair company came out to fix it they drained the system, replaced the bad valve on the radiator, and then went to fill the system back up with water. No water was entering the system and they finally discovered that the feed valve near the boiler was bad (corroded). The feed valve was replaced, this let water back into the system, and they went on their merry way.

About a week went by, and then I discovered that the pressure relief valve on the back of the boiler was leaking water. They came back and said it was because my expansion tank was full. They emptied the expansion tank. (It's the old style -- just one big steel tank, kind of like an oil drum.) In addition, they said they would replace the pressure relief just for good measure. 


About 3-4 weeks went by. Now, the new pressure relief valve on the back of the boiler is leaking (again). 



What can I look at to fix this?



thanks for any help



-B

Mainah 12-01-2008 03:38 PM

sounds like the feeder could be over feeding- drain the excess pressure off and back the feeder off a couple turns-

beenthere 12-01-2008 05:11 PM

Could have a small leak in the expansion tank.
If its at the top of the tank, the relief valve will open before you get water out of the tank.

benjamintr 12-01-2008 05:28 PM

Quote:

Originally Posted by beenthere (Post 192427)
Could have a small leak in the expansion tank.
If its at the top of the tank, the relief valve will open before you get water out of the tank.

Is there any way to test for this?

I'm not quite sure I understand correctly. If the relief valve is supposed to turn on when the pressure hits a certain point, wouldn't the water come out the hole in the tank before the relief valve opens up?

thanks!

beenthere 12-01-2008 05:48 PM

No real easy way.
I usually drain the tank. Refill the system, then shut off the manula valve to the autofeed. If it happens again, its the tank.
Unless you have a tankless coil in the boiler for domestic hot water.


They can have a hole/crack smaller then a pin hole, that will leave air out, but not water.

Mainah 12-01-2008 06:05 PM

Quote:

Originally Posted by beenthere (Post 192440)
No real easy way.
I usually drain the tank. Refill the system, then shut off the manula valve to the autofeed. If it happens again, its the tank.
Unless you have a tankless coil in the boiler for domestic hot water.


They can have a hole/crack smaller then a pin hole, that will leave air out, but not water.

What been said.. with a few steps you can isolate the cause....

benjamintr 12-01-2008 06:36 PM

Quote:

Originally Posted by beenthere (Post 192440)

They can have a hole/crack smaller then a pin hole, that will leave air out, but not water.

OK, thanks for all the info everyone! I'll go ahead and drain the tank again and then shut off the manual valve to the autofeed. If it happens again I'll have the tank replaced.

If it DOESN'T happen after this, I'm assuming I'll go ahead and turn the valve back on. What do I do if it leaks again at this point?

On the small hole... I think what you're saying is that all the air will go out, it will fill up with water, and the "expansion" part of the tank will no longer function. This is what causes the pressure to increase. Is this correct?

beenthere 12-01-2008 11:00 PM

That is corect.
If it doesn't happen with the autofeed manually isolated. Then it is a problem with the auto feed, either leaking through, being set to high, or the manual feed levcer is set to open on the auto feed.

benjamintr 12-05-2008 11:24 AM

Quote:

Originally Posted by beenthere (Post 192440)
No real easy way.
I usually drain the tank. Refill the system, then shut off the manula valve to the autofeed. If it happens again, its the tank.
Unless you have a tankless coil in the boiler for domestic hot water.


They can have a hole/crack smaller then a pin hole, that will leave air out, but not water.

OK, I went ahead and drained the entire expansion tank. It probably took two hours for all the water to dribble out. Then I re-filled the entire system with just enough pressure so that water can make it up to the single radiator on the third floor. Then I shut the manual valve that leads to the auto-feed. Now the pressure relief valve on the back of the boiler has a barely noticeable drip.

This seems to indicate that the expansion tank has a very small leak. Is this correct?

As I said earlier, the expansion tank is an old steel tank. It's in pretty good shape but has a few small spots with signs of rust. However, there isn't any place with a big hole, or a hole large enough for water to come through. Any chance I could just take it down, paint it on the outside with some sort of coating that might alleviate the pinhole? I wonder if there is any way to test it like a tire, put some soapy bubbles on it or something like that...?

thanks

beenthere 12-05-2008 12:05 PM

No coating you can put on that will work.
Replacement is best.

benjamintr 12-05-2008 03:00 PM

Let's say I wanted to replace the old style expansion tank with a newer style one. Are the ones with the bladders better? How would I go about figuring out the size to use?

beenthere 12-06-2008 03:23 AM

Bladder tanks installed properly are better.

You wouldn't like the full formula for figuring out the size you need.

What size is your current tank.
Length X heigth.
There is no harm in oversizing a bladder expansion tank, only undersizing them.

myhouse 01-28-2011 10:10 PM

I have the similar boiler like Benjamin's. I wish I saw this posting earlier. My problem is that: I hired a plumber to do some piping in the bathroom when he was done and he turned on all the knobs(water valves), so it causes the water is dripping out from the Boiler relief valve. Apparently, that plumber is not that smart one and I am so dumb enough to continue to hire him to replace more piping in hope to rectify the issue - I paid him more $, but the issue remains. The next day, I had a technician from Gas company to replace the gas meter, he mentioned to me that the drum tank in the back needs to be drained to relief the pressure. The water pressure is too high. So, the bottom line is that I hired the wrong person for the job. Very mad at myself. Long story short, I had that plumber to replace the relief valve, and he suggested to add the backflow preventer + another valve - these still did not resolve the problem. Now, the problem is that thermostat can't seem to communicate with boiler - it means even if I turn the thermostat to 50F, the boiler still keeps on boiling water and heat still is pumping out from the radiators. On the boiler, there is a small dialer with pointing arrow(Right side says "Open", Left side says "gas valve.."). If I turn the dial to the right side "Open", the heat will kick in even without the request from the Thermostat. If I turn the dial to the Lef Side(Pilot), the heat will not kick in. I feel helpless and so I just called Rooter-Rooter plumbing to get an Free estimates tomorrow. I hope it is affordable. I am still so mad for hiring the wrong people to screw up my boiler. Any feedback on this may help. Thank you so much!

beenthere 01-29-2011 05:32 AM

Might want to get an HVAC tech if you don't want to DIY.


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