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Shutting Off the Water / Leaving Oil Boiler On

Good Evening.

Will premise this post by stating that while I am no expert i have sought professional advice (had a tech from my oil company come out) and have not gotten an answer to my question.

I have a 5 year old Weil McClain oil boiler in my home in my new home in New England. During the winter I travel for work- some times 2-3 weeks at a time.

Prior to leaving, I had shut my water main off and turned off my water pump (circuit breaker). I broke pressure in my domestic pipes using a drain system I have at a low point in my basement. I left my heat on 55 degrees. Checked my gauges (PSI at 16 and temp at 180) and they were at normal levels.

Fast forward two weeks. I return home and notice that my back flow (copper pipe) leaked a tremendous amount and my PSI gauge read 0.00. Called my service provider and was not able to get a clear answer.

Any explanation as to what I'm doing wrong OR what is wrong with my system would be appreciated.


  • JStar
    JStar Member Posts: 2,752

    When the boiler operated, creating pressure, it sought out a point of lower pressure. It found that point in the, now drained and opened, water main. Next time, close the water feed valve to the boiler upstream of the BFP.
  • Michael_J
    Michael_J Member Posts: 4

    JStar, that you very much for the reply. May I ask you to briefly explain what " closing thee water feed valve to the boiler upstream of the BFP means"?

    Also, would it be necessary to have some sort of low water boiler cutoff in place to ensure that the boiler would shut down if it ever did spring a leak?

    Again, appreciate your post. I'm getting a crash course in how these devices operate.
  • Michael_J
    Michael_J Member Posts: 4
    Following Up

    Good Evening,

    Just thought Id check back to see if you'd be kind enough to elaborate a bit further as to how one closes the water feed upstream of the BFP.
  • Weezbo
    Weezbo Member Posts: 6,232
    edited December 2013
    let us see,

    / X +Y / the / is a valve the X and Y the boiler feed regulator and back flow ,

    the boiler is on either end shut off both valves .

    done deal.

    the low water is a great idea you are definitely on the right path there.

    now here is why the boiler and the supply water should both have a valve ahead and downstream ,

    this will valve off the water from coming back at the backflow

    and the water from the supply is valved off so no water can be sent into the boiler .

    the pump is off so logically that wont happen how ever look at it like this ,

    if i have a shut off valve ahead and another down stream , then i can remove the back flow and fast fill altogether and repair them without hassling around with draining the boiler every time ..

    and i can change the back flo and or fast fill out without having to shut off and drain the house side every time ..

    that makes it much easier to deal with .

    the low water may even be required in many instances and even if it isn't it is worth the dime on your time.

    Hope that helps .

    sometimes we use words that make sense to us because that is the words we find easiest ,

    and for the most part we somewhat tend to not notice that ,

    " Huh ? What?"

    look in folks eyes sometimes..

    if i were to say shut off the valve up stream to J star he would shut off the valve up stream closest to the boiler if i said to him shut off the valve before the backflow preventor he might be working on the supply side of the boiler header and think ok and shut the backflow and fast fill out from seeing the boiler done deal.

    if i was working on the water and he asked me to shut the valve off upstream of the backflow i probably would think he means he wants to isolate the boiler and rather than quibble i'd isolate the backflow altogether ..and go on about my work ..

    because when ever you isolate the backflow you have now pressure from the domestic on one side of the devise yet a vac may occur and cause it to leak continuously .

    by locking the conditions down on both sides of the eqasion then nothing flows in either direction except out the back flow ...Maybe ...

    if you leave a backflow where it sees the boiler water pressure and empty space or no pressure on the potable side it wants to dump out the backflow ...

    then because there is no pressure it keeps doing that ...

    thats why the two isolation valves are handy ..

  • M Lane
    M Lane Member Posts: 123

    I'd like to add that a LWCO is one of the most important safeties on a boiler, especially in your situation.
  • Zman
    Zman Member Posts: 7,542

    If you post a picture of the fill valve we can give you more detail.

    Personally, I like to install a spring check valve upstream and forget about it.

    Your back flow preventer is working correctly. You either need to turn off the boiler supply or install a check valve.

    A LWCO is a must.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Michael_J
    Michael_J Member Posts: 4

    Thanks for the replies. I will post a photo next week and bump the thread again.

    Happy New Year!
This discussion has been closed.