Apologies if the title makes this sound rather more than grand than it actually is – it's just a very simple piping system to capture the rainwater falling on the roof and then re-direct it inside the greenhouse.
I started with three 3 metre lengths of 20 mm plastic conduit that I'd bought a year ago for the solar panel installation, before I discovered that I couldn't fit two pairs of cables inside each pipe and therefore ending up buying 25 mm instead for that application.
Two lengths of the conduit I had were white and one black. I had a few fittings already to hand, but topped up the shortfall with a few more from eBay. The inspection covers on the PVC elbows and tee were sealed up using 'Evostik' Pipe Weld adhesive, and then pressure tested by holding my hand over the open end(s) and blowing into the other.
The long lengths of irrigation pipe were drilled every 150 mm or so – I started with 3 mm holes near the feed end and increased to 4 mm and then 5 mm as I progressed further along the pipes, the idea being to encourage water flow along the whole length of each pipe. The open ends are temporarily sealed with blu-tack until I get around to making some proper plugs.
A 22 mm diameter hole was bored in the base of the greenhouse frame to pass the feed pipe through, and then everything was glued-up.
|tee-fitting at the building penetration point....|
|the feed end ( and the recently planted-out tomato plants....)|
The irrigation pipes are supported by short canes with a spring-type saddle clip at three locations on each pipe, to keep them above the soil so the holes won't become clogged with dirt. The canes are simply pushed into the earth.
|full-length irrigation pipes along both sides....|
The downpipe from the roof gutter was cut short and the spout directed into a tundish made from a large electrical junction box I already had in the workshop. This box is made from ABS plastic so it was possible to screw and then glue the outlet and overflow to the PVC fittings. The tundish was positioned to create a head of water of around 1 metre, and was fitted to the wooden greenhouse frame with a few screws.