I was not going to post to this thread anymore but as someone asked !, it gave me the incentive to have a look down there in my wellies after a very powerful thunderstorm today.
Whilst the thunderstorm was in progress, probably about as much rain in as little time as I could ever expect. The flow of water through the chamber was quite something and reminded me of Niagra falls. Quite terrifying to watch but it seems to cope with no problem. I would imagine I would not have had any house left it if I had not discovered the problem.
A few hours later after when the flow had subsided I went down there in my wellies with an inpection lamp to take a closer look and see how much gravel had built up inside the catchpit. There was quite a bit of gravel but I reckon it would take the catchpit 10 years to fill up and I cleared out most of it with a small shovel in about 10 mins, shovelling it into the outgoing pipe.
There was absolutely no cracking or settlement whatsoever so I reckon the job will outlive me. One interesting this is that there is water seeping in under some pressure though one of the joins in the concrete walls so shows the water table is higher than the level in the chamber.
My water harvesting system continues to work well and has saved me over 30,000 litres (I fitted a water meter) of water in 9 months.
Earlier in the year I had to redesign the transfer pump, I had installed a submersible pump above ground for ease of access with a double check valve to keep the pump primed. This worked most of the time, but every 3 weeks or so it would somehow lose the priming and eventually failed after repeatedly running dry. I replaced the pump and fitted it under the water and I have never had any problems since.
The cheap 250w Polish pressure pump I bought has worked incredibly well and is powered from my off grid setup. In summer I pumped several thousand litres continuously on the lawn through the hosepipe over several hours without the pump getting hot. The transfer pump kept up with the hosepipe outflow too, so I had unlimited countinous water.
Another surprising thing is that all the main pre-filter into the harvesting tank and finer pressure pump filter dont even need cleaning after 9 months.
The FINAL picture ?
