Water pressure dropping at hot water boiler.

WhirlingD

Hi everyone…

I had my oil company techs in here a couple of weeks ago to repair pipes in my boiler system that had frozen back in September and burst… Those pipes had been isolated since then, but were never repaired until now.

When they were here, they noticed that my expansion tank needed replacing, so they did that as well.

What I am noticing now is that the water pressure gauge is showing a regular decrease in water pressure from prior to them being here and doing the repairs.

It was typically set, and maintained, somewhere around 18 psi prior to them coming. Lately, when I go down there, I see that it’s way down around 10… So I open the valve to allow more water to go into the system to get the pressure back up to around 18 psi.

I’ve gone down there about a day later, only to see it back down around 10 psi. So I put more water back in. I’ve done this three times just within the last week.

Should I be at all concerned that this is happening? Makes me wonder if there is water escaping somewhere?

Is this expected behavior from this kind of system? I have no idea.

Thank you!

GGross

A couple of possibilities. Air can mess with pressure gauges, could be air working through the system, hopefully a good purge was at least attempted when repairing the pipe section. Could be a leak of course, they can be tricky to track down but losing 8PSI quickly implies there is a decent leak somewhere, if there is a leak you will also get air

What pressure did they charge the new expansion tank to? it needs to be set for the cold fill pressure of the system, and you should not assume the new tank is charged correctly at the factory, this is possibly a separate issue

No this is not expected behavior, the system should be a closed system, you should not need to add water except when you have opened the piping for service. when you are adding water every few days, that means the water is going somewhere.

Some pictures of the installation may help as well. Someone here may see something obvious that you may not notice.

hot_rod

If you set it at 18 psi when it is cooled off, what does it rise up to when hot? The pressure will fluctuate some.
Does it ever go below 10psi? if it drops to 0, you have a leak.

WhirlingD

hot_rod said:

If you set it at 18 psi when it is cooled off, what does it rise up to when hot? The pressure will fluctuate some.
Does it ever go below 10psi? if it drops to 0, you have a leak.

I haven’t noticed it getting below 10 psi… But I put more water in there each time I saw it that low, so I may wait and see what happens over a week.

Thank you for your thoughts!

MikeL_2

  Those pressure gauges are notoriously inaccurate. We keep an accurate gauge on a double end hose for confirming system pressures.......
  

EBEBRATT-Ed

@WhirlingD you can buy a 0-30 psi gauge with a female garden hose fitting and screw it on the boiler drain valve to check it against the boiler gauge. If they don't have one with the fitting on it you can just buy a gauge and the fitting adapter separately.

MikeL_2

WhirlingD said:

If you set it at 18 psi when it is cooled off, what does it rise up to when hot? The pressure will fluctuate some. Does it ever go below 10psi? if it drops to 0, you have a leak.

I haven’t noticed it getting below 10 psi… But I put more water in there each time I saw it that low, so I may wait and see what happens over a week. Thank you for your thoughts!

     10 could be 0, and 18 could be 8 psi. Is there a low water cutoff on your boiler or piping?

neilc

maybe the wife is coming down and setting it back to 10, where it should be(12 really),
why are you running 18psi?
3 and 4 story building ?

HVACNUT

How much of the piping is in a concrete slab?