does the rain barrel have an outlet near the bottom that you could hook up a garden hose to?

That's a clever device. But when I go online and look for it, it's out of stock everywhere I've looked.

You need pressure getting the water to flow in a drip system (15-25 psi), and just getting the water to flow from one place to another in a hose isn't enough if you're using regular emitters. So a pump is smart. But you might want to check out this (page 8) -

https://aces.nmsu.edu/pubs/research/agmech_eng/RR773.pdf

Randy, I have a spigot on the bottom of the rain barrels - about 4-6inches from the bottom and outlets at the top to put tubing that connects the barrels or provides overflow, but not a spigot that you can connect a hose to.

Dan, it does look really interesting, but I didn't try finding it. Out of stock? Too bad. I'll keep looking. That's a great link that covers a lot of information. Thanks.

I found it on Amazon, but the reviews were not great.

'Rain Perfect' Solar Pump

It does offer alternative products on that page....

This seems to be an electric pump, that a lot of people buy...

Popular Electric Pump

When I've looked into information about drip irrigation, I keep seeing advice not to use sources like rain barrel water that might have particulates or algae that could clog the emitters. I don't know if soaker hoses have the same issues.

If you don't have 20 psi, you'll at least need low-pressure emitters. Low psi with high-pressure emitters means that nothing will come out.

Have you tried connecting one of those foam soaker hoses to the rain barrel? You can try to remove the pressure regulator or buy soaker hose for a drip system that doesnt have a regulator. As long as the rain barrel is uphill from the garden bed, shouldnt some water slowly seep out? This would be more along the lines of letting it seep all day instead of just watering for a half hour or whatever one would normally do to reach 1" of water.

So, it all seems to be about the psi - the water pressure. It seems unlikely I'd have 20psi without a pump. I'll have to find out what psi I would have with a pump. If I need low pressure emitters, that sounds like a drip system and not soaker hoses.

I haven't heard of a foam soaker hose, I'll look into it.

I had another question come up. I read on a gardening blog, that because the rain is coming off the roof, that the water is contaminated enough that I shouldn't use it on edible plants. Does anyone have any opinions on that?

I wouldnt hesitate to use roof runoff on my garden but I havent looked closely into the issue. I would be looking for citations to support that claim.

The foam soaker hoses are the ones you usually find in big box stores. They just kind of leak all along their length. The other type of soaker hoses have individual emitters evenly spaced along their length.

Good idea, I'll see if I can find some back up for the idea there is a problem with roof run off on edibles.

i think 20 psi is way more then you need. 10 should be more then enough for drip tape like t-tapes.

Randy - I guess 10psi would be a lot easier to achieve, but not really doing the math, I'm assuming that I'd still need to have it pretty high off the ground to achieve that psi with gravity alone. I have a level lot and with something as heavy as a full rainbarrel, I'm not going to attempt to elevate it beyond two cement blocks high, which is probably less than 3 ft off the ground. I'm guessing I will still need a pump. I am looking at getting an electric pump rather than solar, because all the solar pumps on amazon have less than great ratings from those who purchased them.

That's a good point about t-tapes. Those are low pressure emitters, and work well from 5-15 psi. You get about half the output with 5psi than you do with 15. But you just keep it on twice as long. 10 psi will get you zilch with regular high pressure emitters.

http://www.rainbarrelsoakerhose.com/

they claim it will work with just gravity.

Randy, thanks for that link. I tried to find it on Amazon so it would have reviews, it was there but only through the original seller and with no reviews. I did go back and read that site - and the video on that page was unavailable. But I did find an installation video here, and it shows it being connected to a rainbarrel on the ground......

Rain Barrel Soaker Hose Installation Video

Don't worry about rainwater being safe for plants. All day, every day, you're breathing the same air that rain got any contaminants from. Many places, including much of Australia, use rain water collection from household roofs for drinking water, with or without simple filtration. Don't over think it. Filtration will further reduce your water pressure, and add complications. Your garden soil will be very happy with rain water, which is what it wants, though it wants it as regular rain, which doesn't happen.

Indeed, water coming off a roof is pretty clean. Washed by rain, and what is deposited there is mostly material that gets deposited everywhere. Including in garden beds and your lungs. There is bird poop, but that's raining down on all of your plants anyway.