How to repair a Weil McLain CG Gas boiler
Click on This thumb nail to see a larger picture of this Weil McLain
Boiler that I made repairs to.
This May look familiar to you If you have an older Weil McLain Boiler.
In the following pictures I will show How I made the repairs to this
Boiler. The Call was No heat in the upper zones. When I
arrived I found the boiler hot and The pilot light on.
I also noticed that the pump was working. All of the zone valves were in working
order and were open.
The boiler was working normal. So I checked the gauge and found there was no
pressure in the boiler.
Why was there no pressure in the boiler? This Boiler has a filtrol expansion
tank and fill valve. the tank and fill valve work together to keep the pressure
in the boiler. The pressure should be between 12 and 20 PSI.
So I checked the pressure in the expansion tank (the gray tank between the
boiler and the water heater)
I found it had no pressure, so now I know the tank is bad and needs to be
replaced. but just to be sure I pumped some air into the tank, and as soon as I
did water started to go into the boiler, I could have just pumped it up to 12
pounds and called it a day, But it would not have lasted long and it would have
failed again. And once water was added to the system the leaks showed up. So now I will show
you the rest of the pictures and explain what I did to solve this problem.
This is a picture of the tank and the pump I used to pump it up.
Before you start with this project. Stop and
Think About what it is worth to you and how much money it saved you. And make a
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The first thing to leak was the dielectric union on the return side of the boiler just above the Circulator pump.
and the one on the supply side and the Auto vent leaked from the top and would
So now I have 3 leaks and a bad Expansion tank. you may have noticed that
the expansion tank is stuck behind some pipes and is between the boiler and the water
heater, This is never fun.
FIRST turn power to boiler off. then turn the water to the boiler off. then hook
up a hose to the boiler drain at the bottom of the pipe tight in front of the
bad expansion tank.
Then I removed the auto vent to allow air to come into the top and allow the
water to drain out.
After all the other work is done I will install a new auto vent to solve that
In The Above Pictures I show how to replace the washers on the dielectric union.
Now sometimes the nut will loosen up wit just a few solid taps with a hammer and
a big pipe wrench and some times it just will not come apart and you have to
replace the whole union. In this case the nut came loose. Once I have the nut
off I remove the old rubber washer And clean All of the remaining washer parts
from under the nut. (you have to make sure there is nothing stuck in the nut)
Then I split the red sleeve and put it over the top of the flange and under the
nut and put the new rubber washer between the union then Tighten the nut. This
repair is done.
|Now the dielectric union on the return side above the pump.
Well this "so and so" will not come apart. I tried everything
including heating it with my torch, But it would not give. I have to remove it.
So I cut the copper above the union removed the two nuts and bolts holding the
pump flange to the pump and through it all away, Put in a new flange and tied
back to the copper with a male by copper adaptor and did not install a new
dielectric union on this boiler (a dielectric union is not needed here anyway).
Well Now all that is left is to replace the expansion and fill valve (the Filtrol
System) normally This is a simple and fast thing to do. But This bad design on
the part of plumbers everywhere causes this to be a big deal.
As you can see There are pipes in front of the tank and a water heater to the
left and the boiler to the right and the floor on the bottom and pipes on the
top. What the hell was The person who installed this tank thinking? Must not
have been thinking at all. The sad thing is I see this exact setup every day.
Ok So the tank unscrewed easy and is now sitting on the floor
I removed the handle from the boiler drain so that the fill valve part of the
Filtrol system Will turn.
The copper water line is attached with a compression fitting so I just loosened
the nut and pulled the copper out and held it out of my way
Oh Great even with the fill valve removed and the handle for the boiler drain
gone the tank will still not fit between the pipes. I can not remove this tank,
And I can't get the new one back there either.
So not A new and better plan.
So I stand the old tank up and push it back out of the way. (it will stay there
till the boiler or the water heater heater is replaced) now with some 1/2"
black nipples and fittings I run the pipes in a different direction, facing the
front of the boiler
I install the new filtrol fill valve (this comes with the new Tank) by the way
this is a 110 filtrol If you need to buy this, It looks like the # 30 expansion
tank, But it is different and they are not interchangeable. Then I tie the
copper line into the new fill valve.
Then I screw the new tank on to the fill valve. Now if it has to be replaced in
the future, it's right there in the open, like it should have been in the first
place. Now I put in the new auto vent. and turn the water back on.
But I do not turn the power back on yet because the system is full of air and
needs to be purged.
This is a picture of the return side of the boiler. I have opened all the zone
valves manually and turned all of the red valves off. I hooked the hose to each
of them one at a time and opened the boiler drain about half way (you don't want
to let it run out faster then it goes in)
I like to do is put the other end of the hose into some kind of clear bucket so
I can see the air coming out of the lines and I let the water continue to run
till I don't see allot of air bubbles coming up from the bottom of the bucket.
After this has been done to all the zones. Put the hose on the highest boiler
drain or the one furthest from the pump. start letting the water run from the
boiler drain then open the red valve ( yours may not be red) and then close the
zone valves and let that run till there is no more air. Now you can open all the
valves and turn the power to the boiler back on.
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