Boiler pressure acting strangely

meghanp10

Apologies for the long post.
This morning, boiler pressure had randomly dropped to 2 PSI after sitting around 14 PSI for days. I added water until it was at 12 PSI. Now this evening, around 9 pm, heat was on and the pressure was way up at 35 PSI and the relief valve had not blown! I drained a bunch of water until the pressure was back down to 14 PSI and within 20 minutes it had gone back up to 18 PSI. Could a full expansion tank be causing this? I don't think water is being added to the system since I keep finding it with a very low pressure and have to manually add water.
I'm afraid to leave the heat on tonight but it's -25°C so I don't really want to turn the heat off either..
Obviously, next step is to call a professional, but I'm curious if anyone has any idea as to what's going on.
Thanks in advance!

mattmia2

does it have a bladder type or conventional expansion tank?

HVACNUT

The gauge might not be correct.
If you have a diaphragm expansion tank, does the air eliminator work?
Set the pressure to 12 psi cold.
Shut off the manual valve to the PRV (auto feeder), and keep an eye on it and let us know.
A few pounds plus or minus with cycling isn't a concern.

meghanp10

> @mattmia2 said:
> does it have a bladder type or conventional expansion tank?

Conventional.
Also, an update. I powered the heat off completely last night due to fear and it was at 14 PSI when I went to bed. Now it's at 30 PSI...again.

Zman

If it is gaining pressure with the boiler off, have an issue with either the fill valve or a tankless coil/indirect water heater.

Do you trust the gauge? One of these is an easy way to verify a well as document the peak. https://www.supplyhouse.com/Watts-0069770-IWTG-2-1-2-Hose-Connection-Gauge-0-200-psi?gclid=CjwKCAiAuqHwBRAQEiwAD-zr3b7t6RHA7UM5oFgUzW8EhfkzeR_uAd3paXhkxQhR-HtcvHzWIP8gThoCFt8QAvD_BwE

Are you able to isolate the domestic water?

meghanp10

> @Zman said:
> If it is gaining pressure with the boiler off, have an issue with either the fill valve or a tankless coil/indirect water heater.
>
> Do you trust the gauge? One of these is an easy way to verify a well as document the peak. https://www.supplyhouse.com/Watts-0069770-IWTG-2-1-2-Hose-Connection-Gauge-0-200-psi?gclid=CjwKCAiAuqHwBRAQEiwAD-zr3b7t6RHA7UM5oFgUzW8EhfkzeR_uAd3paXhkxQhR-HtcvHzWIP8gThoCFt8QAvD_BwE
>
> Are you able to isolate the domestic water?

I honestly know next to nothing when it comes to this system. The pressure gauge reacts seemingly correct when I have had to add water so I assume it's working.
It will also randomly drop severely in pressure too and then no water gets added so surely it can't be a leak into the system?

meghanp10

I should also mention it's a very old boiler. Around 100 years old. So it's not surprising that there are issues.

meghanp10

I also just drained water until it was at 12 PSI, turned the heat back on and now the pressure is up to 14 PSI, which I'm assuming is what should happen?

HVACNUT

So according to the gauge we've gone from 2 psi to 35 psi without the relief valve blowing or lack of heat or banging pipes or anything of that nature?
Other than the pressure reading, does everything else seem ok?
Is the relief valve and gauge also 100 years old?
Get it checked out but it could be a faulty gauge.
Pics? I want to see a 100 year old boiler. Dont keep it to yourself.

meghanp10

Pretty much, yes.
My plumber just got back to me and said it's likely the expansion tank is full so the extra pressure has nowhere to go.

Picture of my 100 year old boiler is attached. Haha

mikeg2015

It likely has a Compression tank located up at the ceiling, not a modern , expansion tank.

FYI a “plumber” should not be working on that boiler. It needs a HVAC company that knows how to set up a power burner using a combustion analyzer.

You really, really really should consider replacing that boiler. It likely lacks most of the modern safety devices, and efficiency is probably around 70% at best, if that. I see a damp floor around it, you sure it’s not leaking?

jerryb46

you are not draining the expansion tank right,to do it you need a 5 gal bucket and a 5 ft washing machine hose,Attach hose to tank drain shut off valve to tank coming from boiler,open drain in bucket.will get approx 5 -7 gal of water then its stops now take hose and blow in it you will hear sound of gurgle in tank blow until you can't anymore and pull hose out of your mouth into bucket,move it fast you don't want the black water in your mouth,keep doing this until you get the amount of water the tank holds,the final amount of water will be real sludge close drain open feed to tank let pressure equalize,(may take some time). pressure gauge will should stay steady at set psi,Good Luck

STEVEusaPA

mikeg2015 said:

...efficiency is probably around 70% at best, if that...

I'd estimate 40%-50% overall system efficiency.

Steamhead

mikeg2015 said:

You really, really really should consider replacing that boiler. It likely lacks most of the modern safety devices, and efficiency is probably around 70% at best, if that. I see a damp floor around it, you sure it’s not leaking?

More like 40% efficient, according to one of my Dead Men's Books. That's what we call a "snowman" since it would have been covered with asbestos insulation when it was first installed. This type of boiler was relatively cheap to buy, but it lets a lot of heat go up the chimney.

There is a fair chance you could cut your gas consumption in half when you have it replaced.

meghanp10

@mikeg2015 yes, tank strapped to the ceiling. I have attached a pic. My plumber is HVAC as well. Very small town. Don't have the luxury of a bigger company.
There is some leakage that's been happening for many years according the accompanying rust stains.

@jerryb46 there is only one valve I can open on the tank (see pic). I barely got any water out when I tried draining it.

Steamhead

That's the only drain on the tank? If so it's in the wrong place.

meghanp10

@Steamhead yeah, I thought it was strange. When I fired everything back up, I did hear water go into the tank and then pressure dropped by 2 PSI.

Steamhead

Oh boy. Well, you need someone who knows this stuff. From the label on the boiler, and the fact that your original post mentioned degrees Centigrade/Celsius, I'm guessing you're in the Great White North somewhere?

jerryb46

sent a text about ho to drain ,Steamhead hit the target about the drain in wrong spot (i didn't see picture that is now shows ).Dis regard my lost post

meghanp10

@Steamhead yes, central Saskacthewan.

Steamhead

Unfortunately, our Find a Contractor feature doesn't cover Canada. Hopefully someone will chime in.

BTW, ISTR reading a story in grade school called "Owls in the Family" which was set in Saskatoon.............

Solid_Fuel_Man

That is likely a converted gravity system. Originally had some type of vented tank upstairs (usually in or above a closet in my experience) riveted steel tank maybe. It the 40s or 50s they added a circulator (red pump behind the boiler) and that green compression tank with the soft copper line. I'm guessing you have some nice big cast iron radiators in the house.

meghanp10

@Solid_Fuel_Man yes, steel rads in every room. It works great...when it decides to work. Haha
I just can't figure out this fluctuating pressure situation. It seems to work just fine for a week or two and then it all goes screwy again.

Solid_Fuel_Man

It sure looks like that snowman is leaking

mattmia2

It looks like someone that knew what they were doing did a fair bit of work on it relatively recently.

Does that system even have a relief valve? i don't see one, but we're not seeing much of the near boiler piping. Originally with the open tank at the top of the system it wouldn't have needed one, but when the closed expansion tank was added it should have gotten a relief valve.

meghanp10

@mattmia2 yes, it has a relief valve. Just not visible in the pic.
I've lifted the lever on top of it and it spits water out so I don't know why it didn't release water when the pressure went up to 35 yesterday.
I really have no idea what's going on.

mattmia2

What pressure is the valve rated for?

meghanp10

@mattmia2 it says 30 on the little tag.