Something like this:
enter image description here

but with it designed for the opposite flow of water.

I have a rain barrel that is usually at least half full and it provides enough pressure to use but it's not enough to water my garden efficiently.

Any advice?

  • Agree about backflow. Take these warnings seriously before you make your household ill. How high up is your rain barrel? To boost pressure you could raise the barrel.
    – Stanwood
    Jun 16, 2018 at 5:46
  • In addition to the backflow concerns, it’s not clear to me how this would help with pressure. As I understand it, you want to connect the house to one side, the rain barrel to the other, and run the combined flow to the garden. Since the house pressure is higher than the rain barrel pressure, the flow will always be from the house supply, and will probably back-fill the rain barrel when it’s turned on. I don’t see how it increases pressure in the barrel, other than just keeping the level higher.
    – Mark
    Jun 16, 2018 at 12:08

1 Answer 1


I wouldn't risk connecting the rain barrel to your house's plumbing because you don't want to risk getting non-potable water into your pipes. This sort of arrangement might even be illegal where you live.

What if, instead, you just use a garden hose to add more water to the barrel as needed? Then you don't need to worry about running out. Or, use a quick connect fitting to make it really easy to disconnect your watering hose from barrel and connect it to another source.

  • Why would it be illegal? As well, the pressure of the tap water would be higher than the rain barrel so shouldn't that not be a problem?
    – Allan Cao
    Jun 15, 2018 at 23:49
  • 2
    Read en.wikipedia.org/wiki/Backflow_prevention_device You must absolutely prevent any possibility of water from outside the water system getting sucked back into the general system. Increased demand, pump failure, could all reduce the line pressure enough to suck contaminated water back into everyone else's water supply...
    – DJohnM
    Jun 15, 2018 at 23:56
  • 2
    One Example of thermal backflow: use a hose with a nozzle, shut the valve off at the house but forget to release the pressure in the hose by opening the nozzle. Hose is pressurized to house pressure. Leave the above laying in the hot sun. As the temperature increases so does the pressure. Pressure inside the hose is now greater than household water pressure. Open the valve on the house and water from the hose will backflow into the house. This is before we even add a rainwater source to the mix. Yes backflow must be prevented, and most states have laws requiring wherever there’s potential.
    – Tyson
    Jun 16, 2018 at 2:57
  • There are backflow preventer devices available, but they can be expensive and they're not always legal. My city forbids the connection of potable and non-potable water systems, no exceptions. A neighboring city allows them to be connected if there's a backflow preventer, but the backflow preventer has to be inspected every year.
    – mrog
    Jun 17, 2018 at 4:16

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