Irrigation supply houses are rampant with rainwater/container systems and components these days.
I might try to design a system with the pump in a holding tank with a small, external pressure tank, pressure switch, cycle-stop valve and a carefully designed delivery system, if it was for a customer who is serious.
Too many of them think rainwater is free and limitless. Duh...
Also consider a city water feed (with a backflow preventer) that bypasses the pump and tank for dry times.
Also consider what gets into the tank from the gutters. Leaves, dead birds, etc. It would need some basic filters & filter maintenance....
I feel for drip, you won't be saving much ( Or it will take a while to return your costs for the setup in water savings)
As boots said you couldn't really do too much with a small submersed pump inside a rain barrel.. You can maybe do 1 or 2 drips going at a time, with that point you might as well hand water yourself. Netafim wouldn't work..
The only thing I could see working is a very short looped run of a crappy soaker line.
Thanks guys, this is my owners baby project, we have some recent legislation regarding runoff, so we are doing these barrels as part of our water harvesting package, trying to offer options with them as far as upgrades go. (Frankly, I think it is a tough sell)
I run our lawn care division and am trying to help out. I didn't think we would find any submersibles, Fountain pumps won't work, no pressure build up. ( I am a big fish geek and have tons of these types of pumps and they don't work i this application) I have found a small external piston pump that might work.
I'm in a similiar situation but a little bit larger scale. I have a customer who has a 1500 gallon cistern. There is currently a pump wired to a pump relay that turns on when specified by the controller. The cistern only irrigates 2 zones of drip and the turf is fed by municipal supply. The customer has requested that she would like to add spigots so she can use the water from the tank as she rarely ran the drip this year due to a wet summer. We got ahold of our supplier and said that we wanted to swith the pump to an on-demand pump for the spigots to work instead of using a pressure tank and having the tank visible in the backyard since it is a small backyard.
The drip zones are small so the pump would only need to have a 6-7 gpm flow at a max head of about 8 feet. Our supplier said that would work as I figured so last fall we went ahead and ran the supply lines for the spigots so all we would have to do is swap out the pumps. Well, winter rolled around literally the next day and so the pump swap has not taken place. We were just informed from the supplier that what we wanted (on-demand pump) would not work and that we would need to have a pressure tank. The client really does not want to see a pressure tank so I'm turning to you guys who understand pumps that would work in this case. Any suggestions or do I have to roll with the pressure tank?