Expansion Tank \"Flooded\" Fix

RSGlass

So is it an easy fix when the expansion tank is "flooded"? What can I do to regain the right pressure reading on my boiler? Thank for your help!

Carl PE

That all depends

on what kind of system, and what kind of tank you have. We need some more info.

RSGlass

It's an old boiler (1925) and it's the basic loop system from boiler to radiators and back to boiler. The expansion tank is a small cylinder suspended above the boiler (I don't know the make on this).

Uni R

Draining Expansion Tank

Shut the boiler off. Close the valve leading to the expansion tank from the boiler piping. Then, open the tank's drain valve. It may be less messy to first attach a short hose to the expansion tank drain valve and let the hose drain into a drain. Let the tank empty completely. At this point your tank probably has a great deal of vaccuum (and water). What I do is cup the end of the hose and then blow hard against my hand into the hose. This will force air into the system but it will also help more water to come out so be aware that you'll be draining again. You don't want to taste this stuff! Do that a few times until it is done burping. Then give it a good shot of air and quickly close the drain valve. Next make sure the water feed is on because it will probably need some makeup water. Open up the valve between the tank and the boiler very slightly to let the system equalize slowly. Once you are done, turn the heating system back on, fully open up the valve leading to the expansion tank and return the cold water feed valve to where it was; normally open (no low water cutoff switch) or closed (equipped with low water cutoff switch).

ScottMP

I would not

recommend that any full with thier boiler if they are not familiar with its operation, Certainly not a boiler of the age yours is. There are just to many things to go wrong. Do you have a good feeder valve ?, is it clogged ? will you drop the preasure so low that air gets into the system ? What if the feeder is clogged and over fills the boiler ?

Lastly I see no reason to blow air into an expansion tank. A drained tank will trap atmospheric preasure air and work fine.

If you are not familiar with how the system works you should call a proffensional and have a serviced. Its in yours and your family best interest. This seems like a simple repair but it can be problematic.

Scott

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Uni R

Blowing in the tank...

Scott, unless a conventional tank has something like an Airtrol fitting it won't drain very well. If you let water out and little air gets in, you will just be adding oxygen to the system when you add back new water.

ScottMP

How

will the water get out of the tank and into the system ? If this where tru would'nt all tanks just flood ?

Scott

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Uni R

Two different things...

When draining an expansion tank through a hose it's kind of like putting your finger on the top of a straw, hence the need to assist it. When tanks are in normal operation, you just want the water to compress the air in the tank. The air will push the water back down to a lower level when it cools.


The tough part with conventional tanks is that somehow the air from the tank manages to go strolling to the upstairs branches and eventually you need to drain it again. On the plus side they do tend to last forever. I've just finally gone modern and put a new bladder tank on my system so hopefully this is something that I can forget and learn about new things like whether to get a Spirovent or the new B&G unit. I'm thinking the Spirovent is best. Thank goodness for the wall!

eleft_4

Uni,


If it is not a gravity system, going modern with the bladder tank may teach you a very expensive lesson.

al

Uni R

eleft.

Why's that? It's a diverter tee system with fintube using a circa 1950 Hoffman CI oil fired boiler.