Blockages in the rainwater harvesting system
With rainwater harvesting whatever can go wrong does. After fall I cleared my gutter of leaf debris and left it at that. Silly me! I didn’t consider that the 2″ pipe from the downspout outlet to the storage tank might be clogged with leaves. It was only when rainwater collection by the one tank was less than expected and when, during a downfall, I saw rainwater cascading over the gutter, that I figured I had a problem.
Clearing the blockage was not too difficult. I removed what I could by hand and then expelled the rest with water pressure from the hose. I decided in future to use a mesh screen in the outlet to catch leaves before they enter the pipe. However, I also needed a simple means for identifying and preventing the recurrence of future blockages.
Rather than spray water from the hose onto the roof and let it dribble into the gutter I cobbled together a simple fixture which is attached to a hose and, with the aid of a long stick (or broom), hoisted in place over the gutter. The hose is switched on and water enters the gutter, the downspout and then (audibly) the tank. The bottom left link (in the picture) is attached to the hose. The top left link is sealed and its purpose is probably redundant. Water enters from the bottom left, veers right at the tee and then down at the elbow into the gutter.
How a drip of rainwater produces a flood
The other problem I encountered with my rainwater harvesting was unexpected rainwater loss. During my 7 day vacation to the West Coast there was 0.5″ of rain. I expected all my catchment tanks to rise. However, the carport tank level did not go up, in fact it fell. I did not give this too much thought until I noticed how wet the gravel was around the lower level storage tanks and I then noticed that a connector at the lower level was copiously leaking rainwater from the higher level carport tank. I measured the rainwater loss and it was 250ml in 1 minute (metric is so much easier to use). Which equates to 1 litre in a 4 minutes and therefore 15 litres in an hour. I was gone 7 days which is 168 hours (7×24) which is 2,520 litres (168×15) which is 665 gallons (2,520x.264). So in 1 week I lost approximately 670 gallons of rainwater.
The carport has a length of 27 ft and a width of 24 ft. So the capture/catchment area is 648 sq. ft (27×24). There are 7.48 gallons of water per cubic ft. The recent 0.5″ of rainfall on the carport produced 27 cubic ft of rainwater (648 sq ft x 0.5″/12) which equates to 202 gallons (27 cu ft x 7.48 gal/cubic ft). When I left on vacation I had approximately 500 gals and with the rainfall there should have been say 700 gals and when I returned there was barely any water because I had lost almost 700 gals from leakage.
My solution was two fold: 1) tighten the clamp at the fitting; 2) since the fitting was at the bottom of the hill where water pressure is greatest, I inserted a second valve at the top of the hill where psi is less and therefore there is less pressure to force a leak. For the second valve I used a steel insert into the high pressure end rather than a plastic insert since steel inserts are longer and provide a tighter fit. Hopefully this ends my rainwater losses and my rainwater harvesting will be more efficient.