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Fast fill setting off over pressure valve

Brett18 Member Posts: 3
Hey everyone, I had some work done on our boiler a few weeks ago and was hoping they would purge the system…but they didn’t and now there’s air and now we hear water flowing through the baseboards. So I went to purge the system, and when I used the fast fill it ended up setting off my overpressure relief valve. Now, I had done this in the spring, purged the system, because I replaced a valve and got air into the system, absolutely no issue with the pressure valve going off with the use of fast fill with ~55 psi of city water.  Since then, apparently the over pressure valve started leaking ( 20 years old) and we had the technician replace it a few weeks ago along with installing a couple other shut offs and some other work. 

I initially thought maybe because the boiler was still hot it was quickly heating the new water so it would build pressure/steam, but even when the water flowing through was completely cooled, below 70f, it was still building to over 30 psi within about a minute. This all being said because I can’t really get enough pressure going to push out all the air, I’m kind of worried some of the stuff he installed could maybe be letting air into the system, but I don’t see any leaks anywhere. Also hard to tell if my stupid automatic air bleeder is even working, I can’t say I’ve heard any wisps of air come out of it while purging, definitely seems old though. 

Sorry for the long post, but if anyone has any advice I’d really appreciate it! Thank you!


    EBEBRATT-Ed Member Posts: 12,313
    It could be your feeder leaking water into the boiler

    or a bad expansion tank.

    What type of expansion tank do you have? A plain steel compression tank or a bladder tank?

    I will guess bladder tank and you may need a new one as it could have been damaged by the over pressure.

    When you are purging and fast filling don't leave the fast fill on, bring the pressure up to 20-24 psi then close it then purge if you need more water add some more.

    The big box store may have an expansion tank if it is a common size.

    Be careful taking it off if the bladder ruptured it will be VERY heavy. You will have to drain your system to change it unless you have valve(s) to isolate it.

    If the tank is shot drain the system then drill a couple of holes in the old tank to let air in and water out.

    the new tank should have 12-15 psi air pressure in it (factory charge) check it with a tire gauge before installing
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,775
    If a tech opened up your system to work on it it’s their responsibility to return it to correct operation-properly bleed/purged of all air, and system left with proper pressure,
    Call them back.
  • Brett18
    Brett18 Member Posts: 3
    edited November 2021
    Ebebratt, how would I know, or even check if the feeder is functioning properly? And I have a bladder style tank, I just checked it and it read the system pressure at the time, which was about 17-18psi. But I think something may be messed up, because my back flow preventer now weeps and I’m noticing a small puddle of water underneath it. Maybe a tablespoon or so every several hours. 

    Also so you’re saying I shouldn’t be able to run the fast fill continuously anyways or are you just saying that’s how I should attempt to get the air out? I’m just confused overall that the pressure is even building anywhere near 30 when the drain valve is open…

    Steve you are correct, I’d figured I’d try to work on it this weekend since it’s a hassle to get someone over here, but if I can’t  get it by Sunday we’re calling them back on Monday. 
  • neilc
    neilc Member Posts: 1,808
    the boiler gage might be, bad?
    if you tap on it does it settle to different readings?

    you said 15 - 17, (I assume cold boiler)
    and also 30 and blowing the safety valve, (hot?)
    then I would be looking at replacing the expansion tank,
    check it for water at the air fill, and if you could isolate and drain the tank, check the air pressure,

    is there a manual valve to close before the auto fill? close it and monitor pressure,
    does the boiler also heat the domestic hot water? or is that a separate system ?

    pictures ?
    known to beat dead horses
    EBEBRATT-Ed Member Posts: 12,313

    When you flip the fast fill up it's like putting city water pressure on the boiler which is only rated for 30 psi. You should only use the fast fill to fill an empty system faster (while supervised) or while filling while you purge in both cases keeping an eye on the pressure.

    The feeders come factory set at 12-15 psi and normally shouldn't need adjustment. They can plug up with sediment and not feed, they can occasionally stick and not feed, sediment can ware away the seat causing them to leak by.

    If you shut the boiler off and leave it cold over night with the feeder on check the pressure and check it again in the morning. If the pressure is up the feeder is leaking by
  • Brett18
    Brett18 Member Posts: 3
    Neil, the gauge seems to be operating normally, it’s not sticking or anything. It had cooled down for a while when I took the pressure reading, and it was hot water ~170f at the time I started purging. But it’s not over pressurizing on its own, it was just when I put in the fast fill and walked away to check the hose for air bubbles. When I checked the air pressure on the tank no water came out and I did the tap check on it too and that seemed fine. There is a manual valve I could close to check pressure, I’ll have to try that out. And it just used for heat in our house, 1 story, and we have a electric water heater. What types of pictures would help the most?

    Ebebratt, ok that makes sense. I was wondering if it’s leaking by now, since my back flow preventer is weeping a little. 

    Thank you all for the advice so far 
  • neilc
    neilc Member Posts: 1,808
    on checking the tank,
    by isolating, it's meant that the water side of the tank is relieved to no pressure also,
    a valve alone, without a drain on the tank side is not enough, you would need to loosen, and or remove the tank so no water pressure is present,
    if you loosen the tank, slowly, before the last thread lets go, water would leak out, which might be caught in a pail,

    but maybe we're ahead of ourselves,
    you said you fast filled to 30,
    but then were able to drain to 15 (?),
    at 15 cold, does the system fill higher?
    or if it does when heating, then you need to think expansion tank
    known to beat dead horses