Old Boiler, PSI getting too high

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Old 11-14-08, 06:47 AM
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Exclamation Old Boiler, PSI getting too high

Ok, here is my dillema, we replaced a bunch of galvanized water pipes in the house with PVC, this was to improve water pressure to the rest of the house. One of the pipes we replaced goes to the pressure reducing valve for the boiler (it is a B&G model 12, it is red and have an adjusting screw on the top). Ever since we replaced the pipes and the water pressure has increased, the boiler is holding at around 15-16 PSI when it is off, I know it is supposed to be at 12 PSI for a 2 story house.

I have tried adjusting the screw but the pressure still climbs up to 15-16 PSI. I have backed it off quite a bit, it seems like it just takes longer to get up to 15-16 PSI. I am thinking this needs to be replaced, but I am wondering if I can replace it with a different reducing valve, or if it has to be the same type. I want the cheapest and simplest to install.

I have already replaced my pressure relief valve, because the first time the high pressure tripped the valve, it began a drip leak that would not stop, after replacing the valve that has gone away, however it is still tripping everytime the boiler fires as the pressure is getting up to at least 30 PSI. Any help on this would be appreciated.

I have also emptied the expansion tank as I thought that could also be a problem. Could I turn off the water supply line until I get the reducing valve replaced? If I am correct as long as I am not losing an significant amount of water this would retain the 12 PSI that I am looking for. Thanks.
 
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Old 11-14-08, 01:53 PM
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Yes, you can shut the isolation valve ahead of the make-up reducing valve. Some people (not I) advocate running like this as standard procedure. When the boiler pressure drops below where it needs to be, you can briefly open the isolation valve to restore the pressure.
Doug
 
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Old 11-14-08, 01:55 PM
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This would be more for testing purposes to see if the pressure continues to rise above 30 PSI, correct? I checked it when I got home and the pressure was steady at 8 PSI, so maybe my tinkering with the valve last night got the pressure down somewhat. I also have a bucket under the relief valve to check if I am losing any water throughout the day during normal heating. I am going to adjust the valve again tonight and try to get it around 10 PSI and continue monitoring for water from the relief valve. Are there any other issues that could cause the pressure to be too high during normal usage?
 
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Old 11-14-08, 07:08 PM
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Since you say that you 'drained the expansion tank', I assume you have the large steel type in the ceiling joists, correct ?

Are ya sure you got all the water out ? They do have a tendency to develop a 'suction' or 'vacuum' lock when they are drained... water stops flowing and you think they're empty, but they're not ...

Be patient when adjusting a pressure valve... it can take quite a while for them to stabilize at the new pressure.

I would go only a half to a full turn, then wait at least 10 minutes to see where the pressure goes ...
 
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Old 11-17-08, 06:27 AM
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I adjusted it quite a bit over the weekend, and I think I got it where I need it. It sits idle at about 8 PSI when not in use, then rises into the 20's when hot. I haven't seen any water come out since my last adjustment. I tried to turn it up a little bit (1 turn) to see if I could get it to sit around 10 PSI when not in use, but then some spilled out when it got hot, so I am going to leave it at 8 for now. I checked all radiators and they were hot top and bottom, so there is definately enough pressure.

Yes, it is an old steel tank, what I did was loosen the hose while I was draining it, I would hear the air escape and then more water would come out. I am pretty sure I got it all out.
 
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Old 11-17-08, 05:35 PM
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Your pressure should not swing that far ...

8 PSI ... I hope you've got a ranch home ?

If I were you, I would verify that the pressure gauge is even accurate. . . somethin' ain't right yet ...
 
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Old 11-18-08, 06:15 AM
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It is a two story home with a basement. I know the pressure gauge is working properly around 30 PSI, because the relief valve does not blow until the gauge reads 30 or above. It has not gone up that high though since I turned down the reducing valve. Last time I looked at it cool, it read 8 PSI and when it got hot it was between 15-20 PSI. All radiators in the house are getting hot, upstairs we have 3 radiators, all of them are 2 1/2 - 3 feet tall, the ones on the first floor range, some of them are the short 1 foot tall radiators, and I think one of them is a 2 1/2 - 3 foot one, but they are all different lengths, and there are no radiators in the basement. The pipes are all old galvanized (probably extremely rusty inside if the old water pipes we replaced were any indication). They start out extremely large (not sure the exact diameter) and then they get a bit smaller as they get close to the radiators. I can takes some pictures of the whole setup if you think it would help. Thanks.
 
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Old 11-18-08, 04:06 PM
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Last time I looked at it cool, it read 8 PSI and when it got hot it was between 15-20 PSI
But that's saying something different than this:

It sits idle at about 8 PSI when not in use, then rises into the 20's when hot.
It's gotta do one or the other !

Temperature is important ... the high readings should be noted along with the temperature. If it's climbing "into the 20's", maybe that's when the boiler is at 180 ... and "between 15-20" is at perhaps 140 or so ... ?

Cuz the first case could be just fine ... from 8 to 15 ... would be OK ... from 8 to 20, I'd start thinkin' ... anything more than that, and I'd look for a problem ...

For a 2 story home with the boiler in the basement, well, 8 PSI just ain't gonna cut it ... let's say your highest rad is 20 feet above the boiler. You need at least 8.62 PSI just to get water up the pipes. ( .431 PSI/FT )

On top of that, you really want 4 PSI of headroom, so for a 20 foot height, you would need a pressure between 12 and 13 PSI.

What might be happening is that as the boiler fires, and the pressure climbs to at least 13 PSI, you start to get flow to the upper radiation... and it may be enough to meet the heat load up there... that, and you may also have some gravity flow helping, depending on the piping layout.

I would still verify the gauge ... It could be non-linear ... read OK at higher, off at lower ... you can knock together a 'test guage' pretty easy ... a brass adapter to go from 3/4" FGHT (Female Garden Hose Thread) to 1/4" FNPT (Female National Pipe Thread)... might also find the threads called 3/4 FHT x 1/4 FIPS ... if you can find a 'swivel adapter' use that... pick up a 0-30 PSI gauge and screw it into the adapter... you can also for about $10 pick up a gauge that lawn sprinkler guys use, just for the fitting ... cuz the gauge is too high pressure ... so take out the 'stock' gauge, and put the 30 PSI on there ... put it on any boiler drain... open drain, gauge reads pressure.
 

Last edited by NJT; 11-18-08 at 05:12 PM.
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Old 11-18-08, 04:10 PM
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You might be surprised to find that the heating system pipes are like new inside ... remember that your domestic water is oxygen rich ... lot's of entrained air ... your boiler water is pretty much oxygen depleted ... all the air is driven out by heating and venting. So, there's no O2 in the corrosion equation.
 
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Old 11-18-08, 05:17 PM
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Or, you cold go really DIY and use an old washing machine hose and some stuff from the 'junque boxe' ...

 
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Old 11-19-08, 06:17 AM
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Hopefully I will get this figured out eventually. Let me take a look at the temp and pressure next time so we can figure out what is going on.
 
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Old 12-11-08, 07:28 PM
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Pressure Valve

I have this same problem with my boiler going up to 30 PSI when my boiler runs. Can someone runs me through on how to adjust the pressure valve. Thanks.
 
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Old 12-12-08, 09:54 AM
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Originally Posted by NJ Trooper View Post
Since you say that you 'drained the expansion tank', I assume you have the large steel type in the ceiling joists, correct ?

Are ya sure you got all the water out ? They do have a tendency to develop a 'suction' or 'vacuum' lock when they are drained... water stops flowing and you think they're empty, but they're not ...

Be patient when adjusting a pressure valve... it can take quite a while for them to stabilize at the new pressure.

I would go only a half to a full turn, then wait at least 10 minutes to see where the pressure goes ...
I too thought I got all the water out but I still thought there was more water in the tank. Turns out I was right. On the open/close valve under the tank there is a pinhole that lets air in so the water can come out. It was clogged and as soon as I stuck an unbent paper clip in there and cleaned it out, A LOT more water came out of the tank. Once I did that the pressure in the boiler dropped down from 30 to 12 and has been rock solid ever since.
 
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Old 12-12-08, 06:45 PM
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Unfortunately sometimes ppl get 'stuck' believing one thing or another and usually run around in circles with a problem until they face the fact that their 'assumptions' about what the problem could be get unstuck...

I think it was OldBoiler that said something like:

"Assume nothing. Suspect everything."

And that's good advice... when troubleshooting anything.
 
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