Expansion tank for boilers info

[Denray]

My dad was telling me how if your expansion tank is too small and it leaks out a little water every time it gets hot then the makeup water that comes in brings in oxygen each time and that gives the food for rust to grow. Otherwise it just rusts a bit then stops because all the oxygen gets used up. [:-bigeyes

[mlparham]

My dad was telling me how if your expansion tank is too small and it leaks out a little water every time it gets hot then the makeup water that comes in brings in oxygen each time and that gives the food for rust to grow. Otherwise it just rusts a bit then stops because all the oxygen gets used up. [:-bigeyes

It's hard to argue with Dad.

[rkenney]

Interesting. How does the expansion tank being too small fit into this scenario?

[Denray]

I guess when it can't expand any further it leaks out? Dad is a mechanical engineer too.

[hoosier inspector]

1. A call for heat fires the boiler.

2. The system pressure increases with temperature.

3. An under sized tank (or water logged) quickly reaches capacity and ceases to function.

4. System pressure reaches limit.

5. Pressure relief valve discharges water out of the system.

6. Thermostat is satisfied and cuts out burner.

7. Water cools and contracts, lowering pressure enough (because of x-tank issue+missing water) for make-up regulator to introduce fresh oxygen rich water.

This repeats with every heating cycle.

[Denray]

8. And the rust shortens the life of the equipment.

Thanks Robert.

We just got back from a mad dash to UT and back to get some toys out of Dad's garage (house being sold) for my mechanical engineer son to have at his house. Poor kid.

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