Why does my furnace need an
When water heats it expands and
water can not be compressed, so
without an expansion tank
installed, pressure will build
and cause the relief valve to
The boiler expansion tank
absorbs the expanding water by
allowing the air in the
expansion tank to compress, this
prevents the pressure from
building and allows the boiler
to heat and cool without too
mush pressure building up.
Removing the furnace relief
valve from the boiler or
plugging it so that it does not
leak is a very bad idea, this
can allow the pressure on the
boiler to reach dangerous levels
causing an explosion that can
destroy your whole block. So
don't do that. Now on to the
For the most part Amtrol expansion tank is the most commonly used
other Brands out there and the
work much the same.
For most Residential Boilers the
following 4 tanks are mostly
The # 30, the # 110, the # 15,
and the #109.
Some larger homes need the #60
And they get
much larger but this page is for
So I will not bother with the
Replacing An expansion tank can
be very easy in most cases, but
you are dealing with
VERY hot water and you can get
It may be best to have a heating
contractor do it.
but like the one I did on the
Weil McLain boiler,
turned out to be a real pain.
Before I get into how to replace
it, I should ask, does it really
need to be replaced?
If it is leaking, then it's
simple, It needs to be
Boiler relief valve
If it is full of water, it needs
to be replaced, Tap the tank the
back should sound hollow, if
not, it is full. if it is full,
that means it will be very
heavy, So be careful not to let
drop on your fingers when you
If there is no air pressure
in the tank. use an air gauge
you should have 12 psi. But
remember you let air out every
time you test it. If it does not
have 12 psi you can pump it up
to 12 psi with a pump. But this
is just a temporary patch and it
will go flat again. so it should
Although a water logged
Expansion tank will cause a
relief valve on a boiler to leak
and /or blow off. It is not the
only reason the relief valve
leaks and or blows off.
See why is my relief valve
leaking? by clicking here
#110 and the #30 are the exact
same size tank. but they are not
The #110 is part of a Filtrol
System and only screws into a
Filtrol fill valve. There are 2
types of Filtrol fill valves one
has a valve handle to turn the
water off the other does not. In
the pictures below you will see
the both of them.
Filtrol With Handle and
Filtrol With Out Handle. Click
on Picture for larger picture.
The #110 and the # 109 will only
screw into one of these valves.
The #15 and the # 30 will screw
in to any 1/2" iron pipe size
fitting. The #109 and the #15
are also the same size as each
other. but about 1/2 the size of
the #30 and The #110.
This is a # 30 it
screws into the bottom of an air scoop
This one will be easy to change, but if
it is water logged it will come down
hard once you unscrew it. It is very
heavy when full of water.
This is also a #30 tank And
this would also be easy to
Ok So now we have determined if
we should replace it or not and
what type of tank we need. So
lets replace the thing already.
First Turn the power
to the boiler off. Then Turn the water
to the boiler off. Follow the fill valve
back till you see a valve to turn off.
If you have valves on your supply and
return lines. you may want to turn them
all off to prevent draining all your
|By Thomas Petito