Weil McLain boiler sight glass leak from lower isolation valve stem

SteamBoiler

Folks, this is a new one, my Weil McLain EG-50 boiler sight glass lower isolation valve has started a slow leak from the stem area. I don't understand the plumbing of this well. Once I shut off both the top and bottom isolation valves, the water in the sight glass drained through this leak and I don't see any new water coming out which is good, the boiler presumably isn't leaking out.

I see posts about sight glass leaks but it isn't clear which region exactly typically leaks. I have attached a screen capture from a video, this shows a drop of water forming at the stem of the lower isolation valve of the sight glass. Does this mean the isolation valve itself needs to be replaced?

Thanks in advance, appreciate it and hope everyone is staying warm.

retiredguy

That hex head nut at the drip is the "packing nut". Take a wrench and tighten it just enough to stop the drip.

BobC

The key is to gently tighten that nut. Might want to have a new sight glass and washers on hand just in case that glass breaks. Good hardware stores usually have them, measure the height so you know what size.

Bob

Long Beach Ed

RetiredGuy's advice is right on. There's packing under the nut behind the valve handle. As you tighten the nut it squeezes the packing tight against the stem. If you overtighten, it will be too hard to turn the valve.

mattmia2

Long Beach Ed said:

RetiredGuy's advice is right on. There's packing under the nut behind the valve handle. As you tighten the nut it squeezes the packing tight against the stem. If you overtighten, it will be too hard to turn the valve.

You can also crack the nut if you really wrench on it. If tightening doesn't stop it you may need to back the nut off and add some string packing.

JUGHNE

I open the valve almost all the way up and then tighten the nut a little.
Then rotate the valve handle for just a little more snuging.

The rotation lets the nut turn easier....but don't over do it.

As the packing gets wet, it swells and may seal completely.

SteamBoiler

@retiredguy @BobC @Long Beach Ed @mattmia2 @JUGHNE

Thanks for the comments. For now I have elected to just hand tighten the valve and forgo water in the sight glass, with the deep freeze on. Will try to tighten the packing nut in about a week or so when it gets warmer. That particular valve handle is very easy to turn whereas the upper isolation valve handle, not so much.

As an aside I can't thank the regular posters on this forum - who respond to these questions so quickly - enough. The family loves snuggling up against our radiators and I dread the day when we may need to switch to forced air (those dried out nostril bleeds, blech).

jhewings

I think it would be better to have water in the sight glass even if there is a leak, than no water. The usual advice is don't run the boiler if you can't see water in the sight glass.

SteamBoiler

jhewings said:

I think it would be better to have water in the sight glass even if there is a leak, than no water. The usual advice is don't run the boiler if you can't see water in the sight glass.

Understood, this was a special case of I didn't know what was wrong with the sight glass isolation valve and I do have a probe type LWCO and just before the leak I could see that the water level was fine. The issue is that the boiler was running pretty much for 30 minutes every 45-50 minutes because of the freeze and I couldn't afford to have the sight glass valve fail while I slept.

mattmia2

Over time, like months it will damage the stem of the valve, but it isn't going to suddenly blow out and empty the boiler.

SteamBoiler

Update: I tightened the packing nut some and the leak stopped, after opening up the sight glass isolation valves water is back in the sight glass. However it is bubbling a lot (boiler is off) and water is really discolored so is it possible air got into the sight glass during the leak? My venting is quite poor and only one mains vent appears to work. Will look at possible surges when the boiler runs. Over 9 hours of run time from last night, far beyond normal run times.

neilc

any chance of catching "bubbling alot" in a picture?
or posting a short video?
it may be that the sightglass valves are clogged, bottom one, and you loosened something up,
but I still can't fathom bubbling in the glass

SteamBoiler

neilc said:

any chance of catching "bubbling alot" in a picture?
or posting a short video?
it may be that the sightglass valves are clogged, bottom one, and you loosened something up,
but I still can't fathom bubbling in the glass

Looks like when I open the isolation valve a little, air gets in somehow and there is bubbling in the glass almost like a champagne glass but bigger bubbles. But as soon as the boiler runs the air is pushed out the top. Still not convinced this valve is 100% but there are no leaks right now.

EBEBRATT-Ed

@SteamBoiler

if it's not leaking now with both valves opened (turned to the left) and you can see the water level then leave it alone for now

the clue was that the valve was easy to turn that showed the packing nut was not tight enough.

The valves should turn with slight hand pressure but not be able to spin easily

SteamBoiler

EBEBRATT-Ed said:

@SteamBoiler

if it's not leaking now with both valves opened (turned to the left) and you can see the water level then leave it alone for now

Done, thanks for follow-up!

EBEBRATT-Ed said:

the clue was that the valve was easy to turn that showed the packing nut was not tight enough.

The valves should turn with slight hand pressure but not be able to spin easily

Yup, the lower one was almost spinning and the upper one needs some pressure. Thanks for these clues, really important!