Pressure

What causes too much water pressure in a boiler system?

Domestic hot water coil leaking is one possibility. The other would be the auto fill valve.

Charlie, Dallas gave you a couple common possibilities, if you valve both off and then open a boiler drain in the system to bleed off the pressure you can verify if it is either. Bring each back on line individually and observe the pressure change.

One other possibility is not enough expansion tank capacity or if it is the old style (mounted in the floor joists above the boiler with no bladder) it might be water logged in which case you can drain some water off. There should be a valve located at the bottom of the old style expansion tank.

If none of these are the culprit then maybe your gauge is off, not common but possible.

Okay, no DHW involved. I've had the Prill apart numerous times over the last five day, which is a whole different story. Finally got it fired back up and working again. During this time, I've kept the pump going to try to keep everything from freezing. It was off for almost a full day when the boiler guy came out to tell me that they couldn't fix it When I turned it back on late that night, it did kinda sound like slush was moving through it, but I thought it was okay. The following day, a pipe seperated... the one on the right on the way to the boiler.

So, I turned the water off, turned the pump off and went back to working on the stoker assembly. Finally got that going, turned everything back on and had a couple of leaks.

Tightened them up to a mere drip or two, got everything going, went to town and came home to this blown out and spraying everywhere.

With your boiler in what appears to be an out building the temp in the room could also be a factor. If the room is below freezing the expansion tank might freeze. Maybe more details will help, like what is the boiler feeding, how many zones and type, did it just start higher than normal pressure recently, how high is the pressure, and so on?

I kept the outbuilding heated to try to prevent any freezing. The only gauge I have is the one with temp and ALT (top needle -just what I need, an altimeter???) Then there is this other thing on top. I called around and a plumber will be very difficult to get today or tomorrow. I have two zones, and the thing on the bottom of the expansion tank was also dripping. Be gentle with me - I know NOTHING about plumbing except how to sweat a joint and I'm not showing any pics of my handiwork there.

The whole system appears to be in a "hostile environment" and in need of attention. I believe, you are going to have to do major renovations or, do one thing at a time and expect something else to fail, until all of the weak links are corrected.

I could be wrong.

Don't worry none of us on here are going to criticize your efforts to be self sufficient.

It sounds like your supply pressure may have increased for some reason, is that provided by city pressure? However your water is supplied to the boiler, you need to shut it off after the system is filled and drain some pressure off to see if that is the problem. All the leaks you are having seem to indicate an overpressure and not just a faulty gauge. You can get an indication of the pressure by converting to altitude; 30 PSIG is a little less than 75' of head pressure. Your picture shows the pressure relief valve that is set for 30 PSIG, it may or may not be functioning properly.

On the other hand if your expansion tank has a slug of ice in the bladder it won't allow the increased pressure from heating the water to be absorbed and can be part of the problem.

After reading, and listening, I'd guess Matthaus is close to the reason. I'm guessing, the system has gone off line and frozen. Hot water will freeze in a heart beat ... quicker than cold water. Freezing would account for the multiple problems and high pressures ..... as there is probably ice in the lines, yet.

I wouldn't think pipes are breaking & leaking from too much pressure. I'd guess freezing is the problem. Get a $10 digital thermometer that records high & low & you might get an idea of what the temperature in the building is doing when you're not there. At least it would show the low.

My water is supplied by a well. This past summer, I added an additional pressure tank which has worked well for all of my other water applications. I have turned the supply water off to the boiler. I checked the expansion tank's pressure with a tire gauge on the schrader (?) valve on the bottom of the tank. It didn't have any water coming out of it and read 15 psi. How do I get it down to 8 or 12? I also turned the pump back on. It appears to be running fine as I believe I can hear/feel it inside the house. The only leak was where the gasket on the flange blew out. If you need me, I'll be the one in the outbuilding fixing that.

The most hostile thing about the environment was me when I walked into the spraying water last night. I agree, though. Lots of work to do. I had hoped to have the plumbing be my project for next summer as I have re-built all of the stoker portions as my project this summer.

And have turned off the pump to fix the flange noting that the pump is pretty warm. How do I know for sure that the pump is working?

charlie wrote:My water is supplied by a well. This past summer, I added an additional pressure tank which has worked well for all of my other water applications. I have turned the supply water off to the boiler. I checked the expansion tank's pressure with a tire gauge on the schrader (?) valve on the bottom of the tank. It didn't have any water coming out of it and read 15 psi. How do I get it down to 8 or 12? I also turned the pump back on. It appears to be running fine as I believe I can hear/feel it inside the house. The only leak was where the gasket on the flange blew out. If you need me, I'll be the one in the outbuilding fixing that.

The most hostile thing about the environment was me when I walked into the spraying water last night. I agree, though. Lots of work to do. I had hoped to have the plumbing be my project for next summer as I have re-built all of the stoker portions as my project this summer.

If your system can't withstand 30 PSIG you need to fix the issues that prevent that. In the mean time you can change the pre-charge on the expansion tank to a lesser pressure by bleeding the air out the shrader valve, but there is no guarantee you will get the system down to 8-12 PSIG.
As far as telling if the pump is pushing water, feeling the pipe is the best non-intrusive method I can think of. Maybe others have a better way.

Just make sure you don't leave the feed water off for an extended period of time.