holding boiler pressure

lhedrick

I have a hot water system. Having so plumbing issue and had to shut the ball valve on the inflow. The system operates as 12 PSI. With the inlet close I can't hold pressure. I open the valve pressure builds to 12 PSI, close the valve and the pressure will slowly drop to zero. Pressure relief valve is bleeding water. If the valve is working properly, should the system be abel to hold 12 PSI for a while with the inlet closed? With a working system and the PRV is working properly is it normal for the system to slowly drop below 12, venting to some degree? Like a few days or a week? Or should it be able to hold pressure even with the inlet close.

kcopp

sounds like you have a few things going on... leak in the system and a bad PRV.

lhedrick

I had a main sewer line break and had to shut things down while still keep the house heated with boiler. I see no evidence of any leaks in the heating zone loops. I'm sure it's the PRV, the drain line get hot. I wonder if it's got rust etc in it preventing it from sealing. It's only 1 year old. the back flow valve is not venting. If I can get my drain lines hooked up today. I will try to open the PRV and flush it for a test.

Gordy

Your heating system is self contained once filled the only way water, and pressure can leave is a leak. Sounds like the pressure relief valve needs replaced on the boiler if it leaks water at only 12psi. It should be a 30 psi pressure relief valve. Unless your pressure gauge is not reading correctly.

Gordy

I'm not sure why the boiler needs to be shut down during a sewer line repair?

mak62

You may have a bad expansion tank

Steamhead

I would suspect the expansion tank too. It gives the water a place to go as it expands when heated. If the tank fills with water, the pressure will rise and the safety valve will open.

A pro should handle this. Try the Find a Contractor page of this site.

Gordy

Yes the x tank is suspect. Not enough information. If it were the x tank then the pressure would climb above the 12 psi until the relief pops. I don't know if the op has monitored the whole heating cycle to come to a conclusion.

lhedrick

I too was wondering about the expansion tank. The sewer line issue means I have no drain, so since the PRV in venting it sends hot water down a line which is now under repair. I don't want water running in the hole which has been dug in my floor with a cut sewer line. So I have shut the water inlet valve which feeds the boiler. What I am hearing is that if the PRV, back flow valves and all radiator loops as okay, the boiler should hold pressure even if the input water line is closed. As soon as my drain gets fixed I will try to open the PRV with the lever to see if flushing it will help. It's only 1 year old. Watts Model A, 374A, 30PSI 550,000 BTU.

This boiler system has been giving me trouble for years. The boiler is a Brunham and it's been okay, the trouble has been all the pumps, control valves connected to it. Mostly from hard water. Last year I installed a salt softener and at that time installed a new PRV, back flow vent, 12 psi inlet regulator etc. It all seems to be okay except the PRV. The vent line coming of the back flow valve is cold, no problem there. It's just the PRV. If a flush does not get it to seat, I will just replace it yet again.

Every time I had someone come out, I got a 1 thousand dollar bill and often had to fix it again soon after. So now I save the money and manage it myself since always seems to come to that anyway. Just have not found anyone I can count on so it's do it myself of hire someone who doesn't solve the problem then it's back to me having to do it anyway. It's just hot water and I can handle it. Still need some information from time to time. I know the right person is out there, I just have not been able go find that person and can't keep wasting thousands in the process.

Steamhead

Where are you located?

STEVEusaPA

As other said you may have multiple problems. I just did an expansion tank failure where the tank was full (full of mud) and the nipple nearly clogged. The pressure would go from zero to 30 when running in about 1 minute as the water heated up.

You probably have a gauge problem. Did you confirm pressure with another gauge?
I also had a customer who had a relief valve popping at any pressure between 5 psi and 15psi. Turns out it was really a little over 30 psi. But they kept popping the valve, pressure drops to zero, adding water trying to get to 12, popping relief valve.....over and over again. In the mean time the steel expansion tank got water logged. This is a simple fix, just need someone to take their time and figure it out first before constantly replacing parts.

Alan (California Radiant) Forbes

Fill valve, expansion tank, pressure gauge, relief valve and even a Spriovent can give you pressure problems. It could be one thing or even more tedious, more than one thing.

Yes, in what part of the country do you live?

lhedrick

Steamhead said:

I would suspect the expansion tank too. It gives the water a place to go as it expands when heated. If the tank fills with water, the pressure will rise and the safety valve will open.

It's not the expansion tank. I check it and it okay. It' only a PRV which will not close.

lhedrick

I live near Park City Utah by the way. I have taken over the maintenance of the system myself because over the years I had spent thousand on contractors who have just not worked out. A few years back I had a guy which was good but, he is no longer available. Some one mentioned "have a pro look at it" well that what I had been doing and they knew less then I did. The guys they sent to my place were not the top notch techs which handle the industrial stuff.

I am an electrical engineer and have some background with electro mechanical also and at 62 there aren't many things I have not worked on over the years. I have built my own heat exchangers in the past. As I said due to years of hard water problems I replaced a lot of corroded parts. It was the plumbers who set up my house along the previous owner who didn't even rough in a water softener drain and bypass. No excuse for that and another item I had to do myself. The system was working better then it had every worked after replacing the corroded parts and installing soft water. The sticking PRV thin just started about 4 weeks ago before my drain issues which are not related.

I appreciate everyones input I only wish only my local guy were willing to offer the same help. The gauges were a good suggestion and I will check them out.

Thanks to all and I really appreciate that all of you have taken the time to make suggestions. No matter what I keep learning and hope that always continues.

lhedrick

Swapped out the PRV and now the system is holding 12 PSI and working as it should.
Thanks everyone. Does that mean I'm a pro?

ced48

Gordy said:

Your heating system is self contained once filled the only way water, and pressure can leave is a leak. Sounds like the pressure relief valve needs replaced on the boiler if it leaks water at only 12psi. It should be a 30 psi pressure relief valve. Unless your pressure gauge is not reading correctly.

I know it's not a lot of volume, but what about the air removed by the air separator, doesn't that volume have to be replaced with new water?

Gordy

ced48 said:

Gordy said:

Your heating system is self contained once filled the only way water, and pressure can leave is a leak. Sounds like the pressure relief valve needs replaced on the boiler if it leaks water at only 12psi. It should be a 30 psi pressure relief valve. Unless your pressure gauge is not reading correctly.

I know it's not a lot of volume, but what about the air removed by the air separator, doesn't that volume have to be replaced with new water?

Yes you can lose some pressure through air removal. But this sounds excessive for that theory .