Theoretically, if you could seal the top with a strong, flexible, non-porous material, such as sheet rubber, and place a 20 lb object on top, such as a rock, you could generate 20 lb of pressure. Or you could get an inexpensive water pump.

Raise the barrel

Al

Lee Valley has a special pump, just for this problem, but I can't seem to find it on their website right now. It's a small electic pump (runs on batteries) and if I remember correctly, the blurb said you only run it a few minutes, and once the water is flowing out of the rain barrel well, you turn it off. I think it was around 30 bux CAD.

You might want to give them a call and see if they still carry it...800-267-8767.

Found it!

Here is a link that might be useful: Lee Valley cordless water pump

Thanks Krystine!

I'll try to get more detail information about this pump. Since my purpose is to increase the water pressure (the water come out ok for filling up the watering can, but not enough to use with long garden hose + shower head), I'll need to somehow test it out to see how that works.

I appreciate your info!

-b

place the barrel further off of the ground and let gravity do the rest

Gravity can work & it is more reliable than pumps. BUT the challenge is that you’d have to raise the top of the water by 2.3 feet to get 1 psi, 4.6feet for 2 psi, & so on for any thing more complicated than a simple drip. For example, an irrigation system might need 20+/- psi minimum for its timer, sprayers, or even a standard soaker hose to work properly. So we just use rain barrels & gravity for the garden that’s at a lower grade than the house & mains water for the higher garden.

Put a sump pump in your rain barrel and just turn it on when you need better water pressure and it will shoot the water out like crazy.