With yet another heavy rainstorm, I discovered the rainwater recovery system barrels were overflowing. Investigation revealed that the two end barrels had become clogged with debris from the gutters. I had originally installed leaf traps in the gutter downpipes, but found that these became blocked very rapidly, so I removed them. This was probably not a good idea.
Anyway, I have an old Vax wet-and-dry vacuum cleaner which I normally use for dust extraction for the radial arm saw in my workshop, so used this to clear out the debris from the bottom of the rainwater barrels, and the overflow system is once again working. I’m really impressed with this machine, it’s about 20 years old and still working fine.