Irrigation water recovery

[Leucadian]

Southern California is heaven for growing orchids, but the water situation is not good. Our water is relatively salty and alkaline, forcing many of the commercial growers here on the coast to use reverse osmosis water.

I have been collecting rainwater for the last 2 years, and the plants look terrific, with no leaf tip burn. But it hardly rained last year, and I have nearly exhausted my supply, maybe a couple of weeks left.

I am considering an inexpensive consumer RO system, with the idea of saving the good water for the orchids, and using the rest for landscaping. At the same time, I am planning a greenhouse of about 500 square feet, and I'd like to capture the runoff to send to the fruit trees. I can let the RO system run during the day, powered by solar cells.

My first idea was a cement floor draining into a sump of some sort. The other day someone suggested a plastic sheet (technically a GeoMembrane as used for ponds and catchment basins) with a topping of gravel (and a layer of sand maybe) for the walking surface. That would provide humidity as well, I expect. A third alternative would be a trough system of corrugated fiberglass sheets under the benches, draining into a gutter/tubing system to convey with water for disposition. This would probably be the cheapest but the least elegant solution. I'm leaning toward the GeoMembrane, but don't have a cost yet.

Thoughts?

[fishmom]

I would think that in San Diego, the humidity aspect would be a big plus. Fiberglass sheets would carry the water away quickly, making it harder to maintain humidity.

[Dollythehun]

FWIW, we installed French drains in ours. They connected to a sump. Our water drained away but, could be easily captured and reused. We used a ground cloth with no pea gravel.

[Ray]

I have been using RO for 30 years and building and selling them for 20.

RO systems run off of water pressure, not electricity, so forget your thoughts on "solar".

While you will need a tank to collect the pure water, the handling of the flush water is more about distribution than collection.

Some let it simply spill on the greenhouse floor to provide humidity. Others extend the discharge line (1/4" tubing) out to gardens or other terrestrial plantings. In PA, I used it to keep an artificial pond full outside of the greenhouse, providing water for local wildlife.

[Leucadian]

Thanks for the input, Ray. I thought I'd need a pump to create enough pressure for the RO filter to work.

What is the ratio of pure to discard water in your systems? I'll PM you to continue this discussion.

[Ray]

For the benefit of anyone reading this thread, standard residential systems are considered to be 4:1 systems - 4 gallons in to get 1 gallon of pure water out. By swapping the flow restrictor, it is possible to do 3:1 or even 2:1, although at that pure=flush ratio, the membrane will clog quite quickly.

And so folks don't get confused, a 4:1 system is sometimes quoted as 3:1, where they mean 3 parts flush water to one part pure.