Two expansion tanks in boiler system

[lweeks]

In our house we have a hydronic heating system that has been upgraded over the years. Based on the pipes, it appears it was originally a gravity system with an expansion tank in the attic. Today, we have two expansion tanks in the system. There is a modern Fill-Trol tank at the fill pipe, and there is also an old horizontal steel tank hanging from the basement ceiling.

Based on reading the installation instructions for our boiler (Weil-McLain P-CG), just one of the two is required. I'd like to remove the horizontal tank, it is rusting and the valves are leaking. I'd simply plug the fitting where it branches off. Thought I would ask just in case I'm missing something.

Thanks.

 

[Dana]

If sized correctly for the (very) high system volume, you can do it with a single expansion tank. Whether the newer Fill-Troll is properly sized for the whole system or not needs to be calculated.

Ideally the expansion tank would be located near the intake side of the circulation pump, to lower the potential for cavitation on the pump impeller.

 

[Sponsor]

 

[Jadnashua]

www.watts.com has an expansion tank sizing calculator you can use to determine what size is required. You need to know the volume of water in the system and the min/max temperatures to use it. Other than cost and size, it doesn't hurt to oversize an expansion tank, but you do not want it undersized.