Boiler pressure rising when turned off


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Old 09-30-22, 06:47 AM
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Boiler pressure rising when turned off

Hello I have a very old Crane oil furnace. The pressure keeps rising into the red danger zone even when the switch is off and itís at room temperature. When I drain the system the pressure drops but climbs right back up. When I shut the water off going to the boiler and drain it the pressure drops and stays down. I tried bleeding the radiators but it wasnít air bound. I replaced one of the pressure vent valves on one of the radiators because I broke the little plastic valve trying to loosen it and noticed the water was very dark. Any ideas why the pressure rises even when itís not firing? Thanks in advance.
 
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Old 09-30-22, 10:48 AM
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From your description, I would say the water shutoff valve to the boiler is leaking. When you shut the water off going to the boiler and drain it, I would expect the water to continue dripping. Repair/replace water shutoff valve.
 
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Old 09-30-22, 10:55 AM
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Thanks for the input. When I turn off the water to the furnace and drain it, the pressure drops and stays low. If it was leaking Iíd assume the pressure would rise
 
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Old 09-30-22, 11:19 AM
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There are two valves.... a manual service valve which you are turning off and an auto-fill valve.
It sounds like your auto-fill valve is leaking

The auto-fill would be between the manual valve and the boiler.
 
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Old 09-30-22, 11:37 AM
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Oh gotcha this is the valve between the manual shut off and the boiler. There are 2 in series (I donít know why)

there are 2 pipes coming from the second one. The top pipe feeds the boiler and the pipe coming out of the bottom is I assume an overflow pipe with an open end near the floor
 
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Old 09-30-22, 11:43 AM
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Pressure regulator and relief valve combo.

Similar to the Watts 1450F.
 
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Old 09-30-22, 12:22 PM
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Thank you very much for the link! Do you guys think this is the obvious culprit?
 
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Old 09-30-22, 12:58 PM
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That is a combo pressure relief and pressure reducing valve. If you shut the manual valve off to the boiler and the pressure stays stable with the the boiler off then your feed valve is most likely leaking by. To double check, turn on your manual feed and feel the pipe going into your boiler. If it is cold that is your fresh water feeding in when it shouldn't be.

This is of course if your boiler has enough water and is not calling.

The cap that looks like a flag unscrews exposing a threaded stem with a slot for a flat screwdriver. Loosen the checknut and turn the stem to see if water stops. This stem is how you increase/ decrease the cold pressure to the boiler.

Hope this helps a little.


 
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Old 09-30-22, 01:50 PM
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Thank you very much. I removed the flag and this cylindrical piece and I assume this is what you were talking about. I tried to turn it but it didnít want to move and I didnít try to force it. My question is wouldnít that water coming in always be cold? Sorry if these are dumb questions this is new to me

 
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Old 09-30-22, 02:29 PM
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I see 3 valves in post 5. A shut off valve, a feed water/pressure regulating valve and pressure relief valve, left to right respectively. In response to question in post 3, pressure won't rise when drain valve is open.
 
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Old 09-30-22, 03:06 PM
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Sorry I assume the drain valve is the one at the bottom of the furnace where I can manually drain it to bring the pressure down correct? When I have done this itís just a matter of minutes until the pressure rises again so long as there is water coming in
 
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Old 09-30-22, 04:01 PM
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When I say itís a matter of minutes before pressure rises again itís into the danger zone in under an hour without the furnace on
 
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Old 09-30-22, 04:47 PM
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That pic with the flag in your hand is the correct valve. The other piece that you are holding is the rod which is used for fast filling when the flag is manually lifted when all is assembled. When you get the pressure you want you tighten the nut again and replace the rod and cap.

To get the threaded rod to turn with the screwdriver you must loosen the locking nut first and then turn the stem counterclockwise to see if the water stops. Just like removing a screw, but not all the way. If the water stops then see what the pressure is.

It is cold water coming in so the connected pipe should be cold when water is introduced.

It could be defective or you could have some debris stuck in there.



 
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Old 09-30-22, 05:44 PM
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Thanks again I think I am understanding a little better. I should have known to loosen the locking nut before attempting to turn the screw. Iím not sure what you mean by ďsee if the water stops.Ē Should the water going to the furnace be on when I try this and will I be looking for water to come out the top where the nut is? Should the boiler pressure be at a certain level when trying this? I appreciate the help
 
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Old 10-01-22, 09:25 AM
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With the manual cold water valve turned on besides the pipe going to the boiler being constantly cold if you put the metal end of a screwdriver on the pipe and the other end to your ear like a stethoscope you will be able to hear the water going in.

Those water feeders or pressure reducing valves are factory set to approx. 12 psi. If you have over 12lbs press. in the boiler, unless to manually adjusted the feeder then NO WATER should be feeding in. If you can hear water then your feeder is the problem, either with debris stuck in there or just gone.

If it is feeding unwind the screw and see if it stops, if not put back together and try lifting the fast fill lever {flag} to see if you can clear the debris.

Finally if any of these things work you must reset the valve to the cold pressure you want in your system. I run 18-20 psi in mine for the best results.

If that is the problem you can shut off your manual cold water valve with no danger until it can be replaced.
 
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Old 10-01-22, 11:14 AM
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I don't know if my experience can help. Probably not but here goes.
It might be that the pressure regulator has a way to allow pressure back into the incoming water main.

I know it doesn't sound right but a few years ago the pressure relief valve on my water heater (70 gal nat gas) began leaking slowly. I figured the valve was not sealing well so I replaced it. The new one leaked in the same way.

To make a long story short, I replaced the pressure regulator where the water main comes into my house. That solved the problem.

For the long story, my pressure relief valve had a "bypass" mechanism that allowed pressure back into the "city" main. Here is one but NOT the one I bought.
Valve with bypass

I know that doesn't sound right but it is.
I put a pressure gauge right after the valve and it went to 100 psi, which caused the valve on the water heater to leak and hold there. I guess the pressure in the system was 50 psi where the relief was set but then when the heat came on to the tank the pressure increased. The new valve with bypass solved the problem
 
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Old 10-01-22, 11:31 AM
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Thanks Spott I will give that a shot. Perhaps it is clogged because I got some black water when I replaced one of the radiator relief valves.

PeteCal thanks for sharing your experience. I sure hope thatís not the problem at $2000 😳
 
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Old 10-01-22, 01:06 PM
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A check valve between pressure regulator valve and pressure relief valve will also prevent backflow. What is your water supply pressure? What was the boiler pressure gauge indicating when you drained the boiler?
 
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Old 10-01-22, 06:58 PM
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HighP,
I DID NOT need the $2K one. Mine was about $100, that was 10 years ago or more. I replaced it with the same model number that was installed. It was just one " dome" not two like you show..
 
  #20  
Old 10-01-22, 07:33 PM
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PC,
You had a different situation with your hot water heater. That PRV that you showed is for your cold water main to the house and is used for a different purpose with different pressure settings. It goes from 25 - 75 psi.

The one he needs is made for boiler pressures and is set at 12 psi because your boiler relief valve will go off at 30 psi. Your relief valve on your hot water tank is a T & P valve or a temp. & press. relief valve. It will go off at 150 psi or 210 degrees.
 
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Old 10-28-22, 10:51 AM
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Hello everyone so I ended up replacing the pressure relief/reducing valve. I fed water back into the system (breaker still off) and the pressure slowly climbed over a few hours. I bled the radiators and the pressure returned to normal. I went to bed and this morning I found that the relief valve pipe had been dripping like crazy all night and filled the 5 gallon bucket (this is with the boiler off). So I guess that means the valve is doing itís job but Iím wondering why thereís so much water. Any ideas? Thanks guys
 
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Old 10-28-22, 01:49 PM
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HP,
"So I guess that means the valve is doing itís job but Iím wondering why thereís so much water. Any ideas"

What does that statement mean.

Do you have a tankless coil in your boiler? How is your extrol tank looking. Is it full of water or normal?

With your switch still off and your boiler water still cold what is your boiler pressure?

If you close the blue ball valve off before the PRV/PRV combo and loosen the union there should be no water coming out. Leave it that way and see what happens. If no water comes out your blue valve is holding and whatever is happening is coming from within your system side. I would empty your buckett and see if it continues to leak. If it does and you do have a tankless coil then shut the cold water feed off to the coil overnight and see what happens.

If the relief valve leaks but your boiler pressure gets low then you are loosing boiler water through the coil. Your relief valve doesn't necessarily have to leak at this time. Once boiler pressure gets below 30 psi it should stop. With all cold water feed valves closed and boiler is isolated from outside sources of water, pressure should remain stable and hopefully reveal your problem.
 
  #23  
Old 10-31-22, 09:39 PM
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The most common cause of boiler water pressure rising when off, is leaking regulator valve seat. A far less frequent cause is leak in tankless coil.

In link below with ones with hex plug at bottom have wire screen filter t that can be cleaned by removing plugs. Sometimes valve as to be disassembled to clean the seat.

https://www.supplyhouse.com/sh/contr...ducing%20valve

An easy, low cost way to reduce and eliminate issues is with whole house water $33 filter on line to boiler and water heater. Filter also reduces a common cause of hot water heater failure, water main rust and sediment particles. Big advantage of filters with clear body is seeing element. Did not put filter on main house line because other water uses are not as sensitive or important, i.e. toilets, baths, lawn sprinklers, etc. Also higher volume would require more frequent element changes.

There are many types filters. Here is one: $33 https://www.freshwatersystems.com/pr...-no-pr-3-4-fpt
 

Last edited by doughess; 10-31-22 at 10:30 PM.
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Old 11-03-22, 06:57 PM
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I'm sorry but I do not know if I have a tankless coil. This is not my specialty. I was just trying to figure out why the pressure was so high,m and now I am trying to figure out why I am getting so much water. When I replaced the pressure reducing / relief balve, I obviously had to close the ball valve upstream, and that worked fine. Pressure is between 20-25, but I am getting about half a gallon of water every hour. That seems like alot to me. Expansion tank is 5 years old. Again sorry I'm not good at this but I appreciate the help
 
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Old 11-03-22, 08:01 PM
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HP,
Can you please post some pics of your boiler piping. Feed to boiler, feed to heating units, return from heating units, expansion tank, where you get your faucet water from, how it heats, supply/return to whatever heats your faucet water, all shutoff valves. Please stand back far enough so we can see what pipes go where and what valves shut off what pipes.

Your relief valve should not be leaking at all with anything under 30 psi in the boiler. Your boiler feed pipe should not feel cole but should feel room temp. If cold it means it is leaking by which is unlikely since you said it was new.

You have the RED FLOCHECK with 3 pipes connected and you ordinarily would only have 2. Why the 3 and where do they go. One pipe should be from the boiler, then it should go out to the system on the supply line. It is either fed from the bottom or side with the extra hole plugged. You have 3 lines which is baffling.
 

Last edited by spott; 11-03-22 at 09:10 PM.
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Old 11-06-22, 08:33 AM
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Here are some pics with the pipes labeled. Thanks again for all of the help!!
 
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Old 11-06-22, 12:34 PM
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107019 - Bell & Gossett 107019 - 1-1/4" Straight-Angle Flow Control (supplyhouse.com)

Read the install instructions in the upper right side.


Above is your FloControl Valve which are directional valves only allowing the water to flow in the direction of the ARROW on the valve.That valve allows you to feed it from the bottom or from the side from the boiler to the rads. You are feeding from the bottom which is fine but the side that you have going to your extrol should be plugged and the extrol relocated. The extrol side right now, I don't believe is doing any good because no boiler water can feed from that port so you have no room for expansion when the water is heated.

With the boiler running feel the pipe coming from the FCV to the tank for temp. The pipe should be hot if boiler water is reaching the tank. If luckwarm or room temp then the water is not getting to the tank and the expansion pressure is staying in the boiler and releasing from the PRV.

When you say DEAD END do you mean plugged.

Just a thought.
 
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Old 11-08-22, 08:59 AM
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Thank you very much. Yes the dead end pipe is capped at the end. My buddy thinks it may have been a steam system at one time. So the expansion tank should be on the same side of the red valve as the hot water leaving the boiler?
 
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Old 11-08-22, 12:37 PM
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As far as those capped pipes are concerned I believe they were connected to an external tankless coil that was removed when it stopped working and an electric tank installed. This is just my opinion from the pics and the size and age of your boiler. To switch that boiler from steam to hot water it would have been a great deal of work since nothing from piping to controls is similar to both.

As for the expansion tank location. It must be between the boiler Flo Control Valve (RED VALVE) with no interruptions of water so as the boiler heats up, the heated water has some place to expand uninterrupted to as the tank. How many zones (t-stats) do you have in your system. If you only have one zone you do not need the FCV so you can manually open the valve by unscrewing the red handle or flag on top but not all the way to allow for manual operation and then you can install the tank after the red valve on the copper pipe.

If you only have 1 zone and that FCV has always been there it was installed because you had that tankless and when the boiler ran for just hot water it would not circulate into your heating pipes.

The best and most convenient location in this case would be to add it to that top capped pipe off the boiler and plug the opening where it is now or just close the ball valve and make less work for yourself. First thing to do when tank is removed is check the pressure for 12-15 psi or whatever your cold pressure is.
 
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Old 11-08-22, 12:47 PM
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As far as those capped pipes are concerned I believe they were connected to an external tankless coil that was removed when it stopped working and an electric tank installed. This is just my opinion from the pics and the size and age of your boiler. To switch that boiler from steam to hot water it would have been a great deal of work since nothing from piping to controls is similar to both.

As for the expansion tank location. It must be between the boiler Flo Control Valve (RED VALVE) with no interruptions of water so as the boiler heats up, the heated water has some place to expand uninterrupted to as the tank. How many zones (t-stats) do you have in your system. If you only have one zone you do not need the FCV so you can manually open the valve by unscrewing the red handle or flag on top but not all the way to allow for manual operation and then you can install the tank after the red valve on the copper pipe.

If you only have 1 zone and that FCV has always been there it was installed because you had that tankless and when the boiler ran for just hot water it would not circulate into your heating pipes.

The best and most convenient location in this case would be to add it to that top capped pipe off the boiler and plug the opening where it is now or just close the ball valve and make less work for yourself. First thing to do when tank is removed is check the pressure for 12-15 psi or whatever your cold pressure is.
 
  #31  
Old 11-08-22, 09:18 PM
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Commonly is recommended to locate expansion tank on pump and/or boiler output, with Schrader air valve on top of tank. Tank mounted horizontal or 1/2 nipple on top reduces tank life.

There are insignificant, subtle reasons why some locations are better than other locations. But will not tilt with windmills to explain it. Pascale’s law says any pressure change in equalized in system

DH system with expansion tanks on floor works beautifully (have two 30# tanks). A Ĺ NPT ball valve on bottom tanks nipple makes depressurization easy.

If a bladder goes on one and fills it with water, shut off valve it until replaced. No heavy lifting (25# 15 gal, 50# 30 gal), stress on piping, etc..

There are many comments from HVAC professionals with various “proper” locations. DH uses “best” for home.

 
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Old 11-10-22, 05:37 PM
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Yes I only have one zone so the expansion tank should go here?
 
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Old 11-10-22, 09:46 PM
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​​​​​​ I only have one zone so the expansion tank should go?
Remove drain valve at bottom side of boiler, Install 1/2 Tee. On top tee opening put expansion tank with 1//2 ball shut off on bottom.


Might put second tee with capped nipple filling space to floor .for drain valve. It bladder fails fills tank with water will support it.
 
  #34  
Old 11-11-22, 10:34 AM
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That pipe where you have the arrow is fine. I would remove cap or remove and install reducing fittings and before installing tank off the 1/2" fitting I would install a ball valve and boiler drain if you have the room for ease of testing and replacing or charging if necessary.

Do you have cast iron rads or finned tube baseboard. If you have CI you may need a 60 instead of a 30 if the pressure still rises too much when water temp rises. No. #60 is usually the smallest extrol used with CI due to high water content. Just a thought.
 
  #35  
Old 11-11-22, 10:01 PM
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If bladder fails Watts #30 expansion will weigh 50 pounds subjecting piping to a lot of stress and is heavy to remove.

To avoid those issues DH Posts #31 and #33 below show how to mount tank with Ĺ” pipe on bottom with water drain valve to reduce weight if fills with water.
 
  #36  
Old 11-12-22, 12:32 PM
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A full #30 extrol actually weighs 34.4 lbs. but that is still a lot of weight if you don't expect it. It has a 4 gal. capacity at 8.6 lbs. per gal. = 34.4 lbs.
 
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Old 11-12-22, 12:37 PM
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A full #30 extrol actually weighs 34.4 lbs. but that is still a lot of weight if you don't expect it. It has a 4 gal. capacity at 8.6 lbs. per gal. = 34.4 lbs.
 
  #38  
Old 11-12-22, 10:05 PM
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In alerting DIYers to weight issue DH Post #38 rounded off total weight of water filled #30 tanks to 50 pounds.

Watts #30 Tank weight empty 10 pounds, plus 4.5 gallons water x 8.33 #/gal = 37.48 pounds for full total 47.48 pounds.

OP HighP’s tank is about 72”above floor which may be challenging to some DIYers to hold. To the unknowing , unscrewing that tank could cause injuries. DH pointed out a potential danger, rather than post incomplete data about discrepancies.

https://www.watts.com/products/plumb...nks/etx/etx-30

https://www.watts.com/dfsmedia/0533d...s-etx-etsx-pdf
 
 

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