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I have a residential one-pipe system with a thermopile, no auto feed.
What I am seeing is the pressuretrol is not cutting out at the set pressure,
and not coming back on (I think on mild days when it stays off a while).
(I confirmed that it is the pressuretrol, standing in the cold,
bypassing it for 1 second reboots the system)

I read some discussions here about notoriously bad calibration of pressuretrol
and also pressuretrols that have been harmed by dirty water or high pressure.
I bought a 0-5 lb gauge and some brass fittings and nipples.

I have a few questions to understand how to get reliability:
(A link to a discussion on this is good, I searched and found but not all answers )
1. Can pressuretrols be reliable? I installed this one in January 2014.
Another brand? Switch to Vaporstats?
2. What's a good way to control pressure when calibrating? My bike pump pegged the gauge :-) Mouth? :smile:
3. Do I need to protect the gauge when I am not actively testing?
4. I saw a discussion about dual gauges, but they were in series. I understand why, but I would really need 2 pairs
in series and parallel to protect myself from fail on and fail off. I don't have space or budget for 4 of them :smile: 5.
8. I have a new-in-bag pigtail but I realize it is black pipe, not brass. Is that a Bad idea?

I saw some great ideas on venting, but first I need to get the basic on-off reliable ;-)

Thank you in advance for any suggestions.


  • nicholas bonham-carter
    Definitely, you need a good low pressure gauge to verify the settings of any pressure control device you may have. Put a shut off valve under the gauge, if you are concerned about your pressure exceeding the 5 psi limit, although if that pressure is attained, you will be buying new vents as well, and using the old ones as Christmas tree ornaments! A gauge marked in ounces is best, so you can tell when you have enough main venting, by measuring the back pressure of the escaping air. I don't know of any good reason to have multiple low pressure gauges, so I think you may be confusing this with the code requirement for the 0-30 psi standard, but useless gauge to remain, alongside the new gauge.
    If your present pressuretrol does not even turn allow the unit to come back on, then it is time for a new one, and a vaporstat would be best, as you don't have time to play around with repairing the old one in this cold weather. Sometimes, in adjusting a pressuretrol for its lowest range of settings, the linkage can become unscrewed from the switching mechanism, and cause it not to work. If you later get it working, it could be used as a secondary high limit, in case that steel pigtail becomes plugged up. Go with brass if possible.--NBC
  • Fred
    Fred Member Posts: 8,542
    The first thing to check when the Pressuretrol isn't working is the pigtail it is mounted on. Take the Pressuretrol off and take the pigtail off and see if it is plugged with gunk, a common problem. That would also be a good time to put your new pigtail on as well. As Nick said, if you can go with a brass pigtail, do so. Black iron tends to plug up quicker.
  • Seth Rothenberg
    Seth Rothenberg Member Posts: 26
    I did not get the new pigtail yet, did not put on the new gauge yet...but did check the old one for clogging, AND I have been googling again and again with different keywords, and I just read your post about calibrating a pressuretrol. Incredibly, I found a .05" hex wrench and....perhaps for the first time ever, I am seeing approximately 1.5 psi to approx. 3 psi (with the coarse gauge). Hoping to get the brass pigtail and other fittings to add the new pressure gauge in the am.

    Thanks for both of the comments mentioned!
  • Seth Rothenberg
    Seth Rothenberg Member Posts: 26
    Now that I am on track with pressure control, I am thinking about flushing the system soon. My fresh water feed enters through the wet return. It seems to me that it would be better to flush from above. I think I can put a tee under the tee for the pittail, on top of the LWCO. Or I can put a tee off the "blow down" under the LWCO which is a bigger (3/4") fitting and already has the valve :-) Thanks for everyone's patience as I get around to following the good advice :-)
  • Fred
    Fred Member Posts: 8,542
    Good to hear you were able to calibrate the Pressuretrol. It takes a little patience and only minimal adjustments but once you get it dialed in, they can be very accurate with repeatable performance.
    You can flush the system out by filling and draining several times or by hosing it out from an upper tapping. either way works. Think about doing that after the heating season when the boiler is not hot. you don't want any thermal shock to that boiler block.