My expansion tank has just failed, after only two years. Is this usual? Is this a probable manufacturing fault? Or is this just the expected life of such tanks?
Alternatively was the expansion tank too small (8ltrs on a system with
When the system ran, the water pressure went up from 1 bar to 2.5 bar. More recently it hovered up to 3 bar. Then it failed.
Richard
It shouldn't fail that quickly.
The size could be marginal though. 8 litres is good for up to about
100 litres of system volume.You really need to calculate the volume of water in the system - unfortunately "9 rads, two of which are very big doubles" doesn't give much idea.
Try looking up the radiators on the manufacturer web site. Look for a similar design if you can't find the exact ones, and look for the water content.
Then make an estimate of the pipe lengths and measure sizes - probably mostly 15mm or microbore with 22mm from boiler. Calculate the volumes as though the pipes are cylinders - i.e. pi x radius^2 x length (all in same units). This can be quite a few litres.
.andy
To email, substitute .nospam with .gl
See FAQ. You want around 10% of total system volume as the expansion vessel.
An alternative approach: Try to limit the pressure rise to at most 0.5 bar from full cold to full hot. If you can't do this then there are two way to fix it. (1) Add an additional vessel. (2) If the manufactuers permit, you can reduce the inital charge pressure and the pressure on the dry side of the vessel. (1) Is preferable.
As a temporary work around to get your heating back on. Drain a radiator (or two) and then refill but don't bleed the rad(s). The trapped air will make a good makeshift expansion vessel.
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