Location of backflow preventer for auto fill

[Nanos203]

Hi everyone!

I am installing an auto fill on my pool by tapping into my irrigation supply line. The irrigation system currently doesn’t not have a backflow preventer but I believe I need to install one for the auto fill. I am not quite sure where to install it (e.g. basement, outside on main sprinkler supply, by auto-fill plumbing at pool pad). My yard is upward sloping and the pool is about 20 feet above grade from my house. I’ve read that the or should be 12” above all downstream piping which I think would imply I have to install it at my pool pad. Is that right?

Thanks for your help!

 

[jblizzle]

Mine is just off the side of the pool near where it ties into the water supply line and the bucket that houses the float valve.

It needs to be between the bucket/pool and the water supply line.

Really there should also be on between your house fresh water supply and your irrigation as well.

 

[Chasmengr]

If your irrigation system without a backflow preventer was inspected and approved (atypical) by a code official, then your autofill won't need one either as long as it's connected to and lower than the the highest elevation of your irrigation system. Ask your local code official; if your irrigation system was not inspected and approved, prepare for trouble when you consult a code official (or call from and untraceable phone, and provide no personally identifiable info . . .

If you use an autofill with an airgap, no extra backflow device is ever required. A properly installed physical airgap is the best backflow device that exists and approved by every code in the world. If the autofill's float mechanism admits water flow above the overflow level of the pool, an airgap exists. If the admitted water enters below the pool overflow level, no airegap exists.

Pentair T40 is an airgapped autofill when properly installed. (Hint: level of overflow is critical.)

Chas (retired plumber)

 

[Nanos203]

Hi Chas, thanks for the information. Very helpful. The pump pad is below water level and the house is below the pump pad. With this setup, I think you’re saying the backflow valve needs to be at the pad. Do I have that right?

Separately it sounds like I also may need one for my sprinklers. Where should that one go if I have sprinkler heads that are both below the house elevation as well as above house elevation?

Thanks again.