Boiler Press Low When Off - Over 30psi When On

IamCold

Hi all. I’m new to all of this but have been reading a lot lately. Our system runs too often and our radiators don’t get all that hot. Also the relief valve has been leaking water due to the system exceeding normal pressure when running. 

My gf scheduled someone to come check it out but I believe the company she chose rips people off so I’m a little skeptical of their estimate... they’re claiming we need a new expansion tank (we have the old steel bladderless ceiling mounted kind) as well as a new relief valve, and a new expansion tank for the water heater.

I opened the steel boiler expansion tank to drain it and nothing came out (hadn’t run it this year). Ran the heat, shut it down and got some water to come out of the tank but not much.

The meter on the system reads 9psi when off/cold and is exceeding 30psi and causing the relief valve to open when running.

Given what the tech that came told her, the fact that the expansion tank doesn’t seem waterlogged, the system pressure is low when off but then jumps high when on.. Can anyone offer any insight into what might be going on? If we neee to pay for the service then so be it but I’m skeptical of them based on the prices they quoted for simply changing the hot water heater expansion tank for example. 

Any help is appreciated! 

Jamie Hall

You proobably do need a new pressure relief valve -- if they have been operating, it is best to replace them.

Old style compression tanks work just fine -- when they work. Most modern plumbers have no clue as to what to do with them. If you can post a picture of the tank and the piping which connects it to the heating system, we may be able to guide you through making sure that it works -- although the procedure is simple enough: there should be a valve between it and the rest of the heating system. Close that valve. There also should be a drain on the tank. Open the drain and have patience. It may take a while for all the water to drain out. Close the drain and reopen the valve to the rest of the heating system. Using the system fill valve, adjust the system pressure cold to about 15 psi.

Look around your system -- again, photos of the piping around the boiler and the tank will help. There should not be any device on there intended to vent air -- air scoop or whatever. That sometimes gets added, and it will defeat the compression tank.

One more thing -- no prices, please. One of our rules here. Would you edit your post to take the price out?

Ironman

The tank is most likely water-logged or the valve to it is closed. If a compression tank isn’t leaking, then it should be functional and not need replacing.

You may not be draining it correctly.

Some pics would help.

IamCold

Thanks for the response. Let me know if there are any pictures in particular that would help. I believe the pipe up to the expansion tank is open and clear because I did get some new water coming out after I had run the system, water that wasn’t there after being off all summer.

Do you think it’s likely that I could be trying to drain it wrong even if I was able to get water to come out of the expansion tank until it seemed empty after having run it? Anything you’d advise doing to minimize the pressure while it’s running and keep it in the mid-20’s instead of exceeding 30psi?

thanks again. 

IamCold

Jamie Hall said:

You proobably do need a new pressure relief valve -- if they have been operating, it is best to replace them. Old style compression tanks work just fine -- when they work. Most modern plumbers have no clue as to what to do with them. If you can post a picture of the tank and the piping which connects it to the heating system, we may be able to guide you through making sure that it works -- although the procedure is simple enough: there should be a valve between it and the rest of the heating system. Close that valve. There also should be a drain on the tank. Open the drain and have patience. It may take a while for all the water to drain out. Close the drain and reopen the valve to the rest of the heating system. Using the system fill valve, adjust the system pressure cold to about 15 psi. Look around your system -- again, photos of the piping around the boiler and the tank will help. There should not be any device on there intended to vent air -- air scoop or whatever. That sometimes gets added, and it will defeat the compression tank. One more thing -- no prices, please. One of our rules here. Would you edit your post to take the price out?

Thanks. I edited my post and added a couple photos. The process you cited is the one I followed to attempt to drain the expansion tank. All I got from it was a tiny bit of brown water. Once I ran it a bit I got maybe 16 ounces. 

Appreciate the advice. I’ll try to use the system fill valve to increase the cold pressure. As for the pressure while it’s running being too high, do you suppose the expansion tank really is waterlogged and just isn’t draining for some reason? I can’t imagine how I’d be getting 16 ounces but not the majority of the water out. 

Thank you for your response, I somehow missed it initially and only saw the second persons reply. 

neilc

the tank may be air locked, like an upside down soda bottle holds water, or your finger on the top of a straw,
if you're using a hose on that valve, probably even more locked,
let the valve into a bucket, and see if you can tickle a straw up into the valve hole to break vacuum,
or,
is there any other plug or valve we can't see? maybe where the pipe enters the tank?

IamCold

neilc said:

the tank may be air locked, like an upside down soda bottle holds water, or your finger on the top of a straw, if you're using a hose on that valve, probably even more locked, let the valve into a bucket, and see if you can tickle a straw up into the valve hole to break vacuum, or, is there any other plug or valve we can't see? maybe where the pipe enters the tank?

I did not use a hose, just opened it slowly with a bucket handy. The only other thing on the expansion tank is shown in the picture below. I hadn’t considered it being air locked like that. Definitely will give that straw trick a try. I was 100% convinced the expansion tank needed drained so when minimal to no water came out it really threw me for a loop and sent me back to square one so I’m hopeful that might do the trick. 

Jamie Hall

Try this test. With the valve between the system and the tank open (I think I see one), open the tank drain. If no water comes out, there is something somewhere blocking the tank off from the system. You would need to find that something.

If it passes that test, try @neilc 's suggestion. Open the tank drain with the valve to the system closed, and try to get a length of small diameter hose in through the drain valve and try to force air through it. May be a good deal harder to do than to say, and if you can't do it -- unscrew that valve from the tank (I know, sounds drastic). This will let the water out if the tank is waterlogged.

Gordo

"Don't try this at home"
https://www.youtube.com/watch?v=tWzZ6H57rQI

neilc

you might be able to get that plug to turn, counterclockwise,
then a hose on the bib, and open,
and loosen, but do not fully remove the plug, air should suck in as the plug is almost free of the thread,

IamCold

Jamie Hall said:

Try this test. With the valve between the system and the tank open (I think I see one), open the tank drain. If no water comes out, there is something somewhere blocking the tank off from the system. You would need to find that something. If it passes that test, try @neilc 's suggestion. Open the tank drain with the valve to the system closed, and try to get a length of small diameter hose in through the drain valve and try to force air through it. May be a good deal harder to do than to say, and if you can't do it -- unscrew that valve from the tank (I know, sounds drastic). This will let the water out if the tank is waterlogged.

With the valve between system and tank open I get a strong flow of water from the drain valve. Will try closing that valve and getting something up into the drain valve. If water is coming out with the valve open, wouldn’t it come out just as well with the valve closed? Maybe not... I’ll definitely give it a try as soon as I locate something to use for this purpose. 

When you say unscrew the valve if necessary, you mean the valve pictured in my most recent photo? The fairly rusty thing on the opposite side from the drain valve? 

Jamie Hall

IamCold said:

Jamie Hall said:

With the valve between system and tank open I get a strong flow of water from the drain valve. Will try closing that valve and getting something up into the drain valve. If water is coming out with the valve open, wouldn’t it come out just as well with the valve closed? Maybe not... I’ll definitely give it a try as soon as I locate something to use for this purpose. 

When you say unscrew the valve if necessary, you mean the valve pictured in my most recent photo? The fairly rusty thing on the opposite side from the drain valve? 

Not necessarily. If the tank is turly waterlogged -- which it's beginning to sound like -- it will hold water when the drain valve is open, as @neilc said, unless some way to let air into it is found, but when you force water into it (from the system) it has to go somewhere... out the drain.

The valve I mean you to unscrew -- but only if all else fails -- is the drain valve/hose bibb on one end of the tank. Or you could undo that square plug, if you can get it free, as he suggested.

IamCold

neilc said:

you might be able to get that plug to turn, counterclockwise, then a hose on the bib, and open, and loosen, but do not fully remove the plug, air should suck in as the plug is almost free of the thread,

Damn, this makes me nervous. No concerns with the age or apparent rust there? I’m just concerned I’ll end up being unable to seal it back up properly and have to replace the whole expansion tank if that happened. If that’s the only way then so be it but I think I’m going to give this straw/hose through the drain valve a solid attempt prior to resorting to this. 

neilc

Gordo's video is interesting,
Yuk

IamCold

Jamie Hall said:

Jamie Hall said:

With the valve between system and tank open I get a strong flow of water from the drain valve. Will try closing that valve and getting something up into the drain valve. If water is coming out with the valve open, wouldn’t it come out just as well with the valve closed? Maybe not... I’ll definitely give it a try as soon as I locate something to use for this purpose. 

When you say unscrew the valve if necessary, you mean the valve pictured in my most recent photo? The fairly rusty thing on the opposite side from the drain valve? 

Not necessarily. If the tank is turly waterlogged -- which it's beginning to sound like -- it will hold water when the drain valve is open, as @neilc said, unless some way to let air into it is found, but when you force water into it (from the system) it has to go somewhere... out the drain. The valve I mean you to unscrew -- but only if all else fails -- is the drain valve/hose bibb on one end of the tank. Or you could undo that square plug, if you can get it free, as he suggested.

Gotcha. That makes sense. I’ll be giving this a try first thing in the morning. I’m actually very relieved that everyone seems to think it’s waterlogged. That I think I can end up working out, if it’s something else entirely that needs diagnosed I’m in trouble. I’ll follow up on how this turns out as soon as I can try getting something up into the drain valve and follow up. Thanks again! 

JUGHNE

Are you sure the valve between the boiler piping and the tank is open?

That tank is hanging by strap?
You have a little wiggle in the hanging or even you can push up on one end of the tank. If full it will feel like a full keg of beer if you can relate to that.
If empty easy lift.
Also tap with a tool....might sound hollow/tinny or a thud of full.

Try the Gordo method or a double female ended hose connected to some water supply. Very carefully shoot house pressure into the tank.
Over 30 PSI will open your boiler relief valve.

IamCold

Gordo said:

"Don't try this at home" https://www.youtube.com/watch?v=tWzZ6H57rQI

I used this method and it worked like a charm. Had to blow through it probably 30 times to empty the whole thing. The work became less and the flow of water increases as time went on. 

The cold pressure in the system seems to be even less now, looks like maybe around 6-7psi. I’m not familiar with using the supply valve to increase the pressure up to around 14psi or so as was suggested but I should be able to find a good video. After that I’ll give the system another test. 

IamCold

I’m struggling with determining what is the supply valve to open and increase the systems pressure. I saw a video that showed how to do it but did not help at all in determining which one is the supply valve. Can anyone help me figure that out? I think I should be in good shape after that. 

JUGHNE

So it may have felt like a full keg of beer.
Now with it empty you can shake it around and tap it to know empty.

When it is good to go it will be 2/3 water with 1/3 air on the top.

I isolate the tank from system, then get the pressure up to where you want it at 15 or so.
If the pressure fill valve is working correctly, you could bleed air from rads.
When that is done then open the tank valve and then fill valve will add more water to partially fill the tank.

Any air in the system should eventually end up in the tank.
You want no auto air vents on this system or the tank will loose the air and become waterlogged again.

If, after the tank is in the system and you have to bleed a lot of air out of rads, you may have to do the drain procedure again. But isolate the tank for draining.

Ideally you want no air in the rad and piping.
If you have the system bled of all air possible, you want to isolate it from the tank if you have to drain the tank again.

Any air that comes out of the the water should end up back in the tank

IamCold

JUGHNE said:

I isolate the tank from system, then get the pressure up to where you want it at 15 or so. 

I’m ready for this step but having trouble knowing which valve is going to increase the system pressure. I really only see two valve essentially. The one that I close to isolate the expansion tank and then one other (it is seen on the far left of the bottom picture of the two I most recently posted). Is that likely the correct one to open to increase system pressure? 

EBEBRATT-Ed

@IamCold

The valve to add water to the system is the blue handle valve on the left facing the front of the boiler, maybe 18" above the top of the boiler with the BX cable running down it. That is the city water fill you can trace it back to your cold city water. After the valve it drops down and turns and goes into the blue pressure reducing valve that feeds water into the boiler.

That valve is usually left wide open (unless there is a problem with the prv leaking by). The prv should maintain the boiler water pressure at 12-15 psi when the boiler is cold

PC7060

Open the twist valve on the supply side of the blue pressure regulator. That will allow water in which will bring up the system pressure to the psi level of the regulator. 

IamCold

EBEBRATT-Ed said:

@IamCold The valve to add water to the system is the blue handle valve on the left facing the front of the boiler, maybe 18" above the top of the boiler with the BX cable running down it. That is the city water fill you can trace it back to your cold city water. After the valve it drops down and turns and goes into the blue pressure reducing valve that feeds water into the boiler. That valve is usually left wide open (unless there is a problem with the prv leaking by). The prv should maintain the boiler water pressure at 12-15 psi when the boiler is cold

Thank you. As one update, my system pressure is now showing 0 psi. But yeah, so the blue supply valve you mention is indeed open right now. I was expecting it to be closed and to open it to increase pressure. The person that came did mention that we needed a new pressure relief valve. Given that the supply line is open and my system shows 0psi is it likely caused by the prv? It worked to relieve pressure when my system hit 30psi but maybe it is not working to maintain the minimum pressure? Would that make sense? 

PC7060

PRV is the relief valve that releases water when the boiler internal pressure exceeds the rating of the valve. It’s located on the side of the boiler just behind the circulator. 

The blue pressure regulator is used to reduce the system pressure from domestic system (45-60 psi typically) to the 12-15 range needed for the boiler. 

If the pressure is not coming up with the supply valve open to the regulator I’d say either the supply valve or the blue regulator is bad. 

Make sure the valve to the air tank is open too. 

IamCold

PC7060 said:

Open the twist valve on the supply side of the blue pressure regulator. That will allow water in which will bring up the system pressure to the psi level of the regulator. 

The trouble here is that valve is already open. And my system pressure sits at 0psi and I hear no water being let into the system even with that blue valve open. 

JUGHNE

I see only 2 valve/stops on your system. Each have a blue wheel handle.
You have the isolation one for the tank.

The other to the left is the water supply, it is typically left on feeding the (blue) pressure reducing valve (PRV) it is connected to. (the blue device is a water pressure regulator which should maintain the 15 psi or so that it is adjusted to).

If the water supply is off, turn it on and watch the pressure gauge.

If it is on then the PRV needs adjusting.

There is usually a locknut on the top stem and you turn the stem CW to increase the pressure while you watch the gauge. It will be slow to respond and often a little finicky in adjusting.

If you get it working to build pressure, you could then check rads for air.
It would be good to have a helper in the basement to watch that the pressure does not go to high as water is added. The PRV could be jumpy in regulating pressure.

Did you have the tank isolated when draining?

If not then you would be draining the entire system, a lot of buckets, not what you want to do.

Usually for a new install one would add valves to isolate the rad system from the boiler to avoid draining the entire system down for minor repairs, such as changing the relief valve, pump etc.

EBEBRATT-Ed

@IamCold

Some confusion.

Pressure relief valve (PRV) is on your boiler opens to dump water out of the boiler if the pressure exceeds 30 psi

Pressure reducing valve (PRV) or feeder is the blue valve that feeds water into the boiler to maintain 12-15 psi.

If your boiler has 0psi. the blue PRV may be stuck or clogged.


If the blue feeder won't feed. get a garden hose and hook one end up to your city water cold water at a hose bib or at your washing machine connection. Connect the other end to your boiler drain valve and feed the water into the boiler through the hose. Use a washing machine hose on the end of the garden hose to make the connection.

Feed the water until you get 12 psi and bleed as @JUGHNE mentioned

JUGHNE

The industry, after more than 100 years, has not settled on the correct abbreviations for devices. One is pressure relief "pop" valve and the other is fill regulating valve.

If you loosen the lock nut on the stem and then rotate the stem CW you may get some flow.

IamCold

JUGHNE said:

I see only 2 valve/stops on your system. Each have a blue wheel handle. You have the isolation one for the tank. The other to the left is the water supply, it is typically left on feeding the (blue) pressure reducing valve (PRV) it is connected to. (the blue device is a water pressure regulator which should maintain the 15 psi or so that it is adjusted to). If the water supply is off, turn it on and watch the pressure gauge. If it is on then the PRV needs adjusting. There is usually a locknut on the top stem and you turn the stem CW to increase the pressure while you watch the gauge. It will be slow to respond and often a little finicky in adjusting. If you get it working to build pressure, you could then check rads for air. It would be good to have a helper in the basement to watch that the pressure does not go to high as water is added. The PRV could be jumpy in regulating pressure. Did you have the tank isolated when draining? If not then you would be draining the entire system, a lot of buckets, not what you want to do. Usually for a new install one would add valves to isolate the rad system from the boiler to avoid draining the entire system down for minor repairs, such as changing the relief valve, pump etc.

I did have the expansion tank valve closed when draining. I got about the right amount that I expected out from the tank. The locknut on the supply stem now wants to leak on me after spinning it open slowly. And even with the supply valve open, I’m not hearing any water enter the system. I’m wondering if maybe this valve and the PRV are both shot or something? 

JUGHNE

Did you rotate the shaft?

PC7060

For clarity I recommend you use the descriptive name in the posts. For example the "over-pressure relief value" and "input supply pressure regulator".

The over-pressure relief value would not cause this problem.

The problem is mostly like the input supply pressure regulator as @EBEBRATT-Ed & @JUGHNE mentioned.
Could be the supply valve but you can check this by loosening the nut (carefully) on the input supply pressure regulator to see if water comes out.

JUGHNE

If you need the heat, you can back fill the boiler as ED said.

If the fill valve does not work, sometimes it has a screen on the inlet that plugs.

But most likely replacement is the best way.

If you replace it, I would also replace the relief "pop" valve.

As you will have to drain the entire system down, replace the parts and then refill.
And bleed air from radiation.

IamCold

JUGHNE said:

Did you rotate the shaft?

Honestly, not sure what you mean. Sorry. I'm confident I did not do that though. The only things I've rotated have been valves and the small finger fitting on the side of the supply line valve, which is now wanting to leak.

PC7060 said:

Could be the supply valve but you can check this by loosening the nut (carefully) on the input supply pressure regulator to see if water comes out.

When I loosen the finger tight fitting on the side of the input supply valve, it is leaking. Not sure if that helps at all, likely not. I have not loosened the nut on the input supply pressure regulator just yet.

JUGHNE said:

If you need the heat, you can back fill the boiler as ED said.

If the fill valve does not work, sometimes it has a screen on the inlet that plugs.

But most likely replacement is the best way.

If you replace it, I would also replace the relief "pop" valve.

As you will have to drain the entire system down, replace the parts and then refill.
And bleed air from radiation.

So at this rate it sounds like I would need to replace the input supply valve, the input pressure regulator and the pressure relief valve?

PC7060

That’s what I’d do.

JUGHNE

Did you loosen the pack nut on the blue wheel handle valve?
No, that is not the one, tighten it back up to where it just stops leaking.

I mean on the blue fill valve there is a lock nut on the top to allow you to turn the vertical stem. Loosen the nut and rotate the shaft CW to allow pressure to go in.
It may or may not work.
You may be able to download instructions for that fill valve.

If you have to change anything, it would be the fill valve. The water supply valve is most likely ok after you tighten the packing nut.

And because you have to drain the entire system, it would be wise to change the pressure relief valve (pop) on the left rear of boiler. If you don't and it will not seat to stop dripping, then you will have to drain the system again.

IamCold

JUGHNE said:

Did you loosen the pack nut on the blue wheel handle valve?
No, that is not the one, tighten it back up to where it just stops leaking.

I mean on the blue fill valve there is a lock nut on the top to allow you to turn the vertical stem. Loosen the nut and rotate the shaft CW to allow pressure to go in.
It may or may not work.
You may be able to download instructions for that fill valve.

If you have to change anything, it would be the fill valve. The water supply valve is most likely ok after you tighten the packing nut.

And because you have to drain the entire system, it would be wise to change the pressure relief valve (pop) on the left rear of boiler. If you don't and it will not seat to stop dripping, then you will have to drain the system again.

I gotcha now. I have done nothing whatsoever with the blue fill valve. I was referring to the blue wheel handle valve (which was open to begin with) and that I spun the thing on the side that now wants to leak on me when the blue wheel handle is open. The "thing in the side" is circle in red in the image below. I will try what you're describing with the blue fill valve.