Why dont you try an RO system on your well and store that water?

That was what I was going to suggest. A Reverse Osmosis filter system. If you look on the label of bottled water, much of it has been filtered through RO

Give you an idea of how much they cost. Not too bad...

Here is a link that might be useful: RO systems

I have an RO system...90gal/day, with a gigantic deep well bladder storage tank, booster pump, permeate pump, the whole 9 yards. But it has downsides. I'm going through 2 membranes a year ($75 each), 4 filters a year ($10 each) and the system wastes a lot of water.

A rainwater tank here costs about $500 for 500gal. We plumbed one in a few weeks ago for about $50 extra materials, and $150 for a demand driven pump. Years ago I wrote a guide on how to size water tanks. I would have thought that in much of the greenhouse portion of the US the water off the roof would make a sizable dent in the water use of greenhouses.

Also considering recirculating water - it's best to do this with a pond with fish and stuff in it to break the pest cycle, or use a concrete holding tank with a UVC steriliser in it. I use both and have never had problems.

Here is a link that might be useful: Rainwater tank howto

Thanks, Nathan, I marked it.

And I'm bumping to see if I can get Chris to bite.

I thought that some time ago Chris mentioned that he was designing a rainwater collection system for his GH. Based on the number of replies, few people are doing this. I'm going to have to do something, though. I tried watering everything using RO tank water and I used all of the draw down. If I do that during the spring and summer, I'll be going through membranes every 6 weeks...

Not biting on this one.....

This one is too close to home, this is something I REALLY need by Feb and as rainwater is usually a solid until April I have some serious thinking to do.

Well biting a little bit.

The tank, that is the key. Where are you going to store what you collect?

I am trying to get hold of one or more of those tanks you see in spring that the farmers use to truck water to fields when they are spraying.

If I do I have two options. Dig a big hole and bury it or stick it in a barn (I have a couple to choose from!) or the hogless hog shed and cover it in straw bales.

As to May to September storage I am thinking pond.

The Netafim drip tape I irrigated my field crops with last season made a dramatic improvement on both yeild and quality, but I am not happy about the amount of iron and other crap I pumped out there.

As to greenhouse water. I am going to install gutters and bring rainwater and snowmelt into the greenhouse and store it inside.

A sump pump in a rain barrel in my greenhouse has enough pressure to water seedlings.

My rainwater tank is a concrete cistern under the greenhouse, with polystyrene insulation to the ground. It is 1.5 m (5') deep, which is deep enough to crawl around in when it's empty for cleaning and stuff. It also gives a reasonable thermal mass, and I use it in a closed loop with the bathtub for the fish. (which means it is fairly high in nitrates :) UVC sterilizer bulb is mounted inside which keeps the water clear and sweet. My drinking water is a polyethylene commercial tank.

You both have touched on a couple of the issues I'm swirling around in my head. First, location of the tank. The websites I have looked at all seem to locate the tank outside. But, like Chris, I'm leaning toward locating the tank inside. Some of my plants do not like being watered with cold water.

Then where? Buried tank makes sense space-wise, like Nathan has done.

And what about the thermal mass issue? Is the thermal mass important if the tank is buried? Will the heat absorbed by incoming cold water in the winter offset any gains in the form of heat released once that water warms up?

Chris, does a sump pump generate enough PSI? I need at least 25 PSI if possible. Nathan, what kind of pump do you have?

Wow, sorry for all the questions, but one more...what kinds of filters do you have on your system? I've seen screens, sponges in the downspouts, first flush diverters.

Thanks, guys. SB

In my case the thermal mass is adjustable - I can run the water through several different loops for heating or cooling (where I live cooling is more of an issue than heating) using the sun to heat (black pipe in the sun) or evaporation to cool (using a swamp cooler as a water cooling system).

I use some cheap high head low flow centrifugal pumps for moving the water round (they are each rated at 25W) and a 250W centrifugal pump with pressure vessel and pressure switch to supply the sprayers. Another advantage of my layout is all the excess water runs back into the tank (but I don't wish to drink that water). I can do this because I don't use any fish toxic chemicals in my greenhouse, and because I have a UVC sterilizer to prevent the water going stale and killing my fish.

It may not be practical in colder climates where the tank could freeze solid, though heating your greenhouse by heating the stored water may be an efficient way to spread the low grade heat evenly through the greenhouse.

The roof runoff goes directly into a mini-bog garden (in the greenhouse) which filters out the dust and dirt fairly effectively. First flush diverters are a cheap solution and do remarkably well - just put a vertical pvc pipe inline before the main downspout and add a single dripper to the bottom.

A sump pump will probably be suitable to drive drippers, but I don't believe that they have a pressure cut-off switch or checkvalve so you'll have to control your irrigation by switching the pump on and off. If you want to drive misters you'll probably need a proper pressurising pump.

Excellent information, Nathan, thanks.

Couple more questions, if you don't mind...

Regarding the thermal mass (swamp cooler/black pipes), how do you control which system is in use? Manually?

Regarding the bog, how do you control the flow of water inot the bog during a heavy downpour? How do you keep the bog medium (peat or whatever) out of the tank?

TIA, SB

Each loop has its own pump, there are no valves (to reduce pump loading). The pumps are controlled by a custom controller consisting of a modified MD420 driving some relays.

For the downpipe I have a simple rate limiter consisting of a piece of 100mm pvc pipe with a slot cut into the base. If the water comes in faster than that, then the water overflows directly into the cistern. In that case the majority of the dirt has already run into the bog so it doesn't worry me.

To stop the peat escaping (which is actually 7mm road metal and composted 'tip mulch') I use a row of local reed species around the outlet which trap leaf litter and whatnot and a thriving ecosystem including drosera, twigrushes, sphagnum and alpine grasses to stabilise new dirt. Everything is either heavy duty, non-contact or biological - those are the things that work in this environment.

Very cool. Sounds like too much for my little GH, but maybe a simplified, smaller version would work. Thanks. SB