On Oct 14, 9:29*am, wrote:
I have a new plaster pool and they use lots of acid for the first year
or so. *I've plumbed a line from the inlet side of my pump to a tank
with 3 parts water, 1 part acid. *I'm using *irrigation drippers in
line to regulate the flow and have it just right so it keeps the pool
pH level correct. *I know of other people who have done this and it
works long term.

My problem is that when the pump shuts off, a small amount of the acid
still siphons into the pool plumbing. *Maybe because the tank is
slightly higher than the pool level? *Its about a quart over night.

I was thinking maybe a small spring loaded check valve would help,
where just the spring pressure would be enough to stop the siphon
flow, but when the pump is on and creates a vacuum, it would be enough
to move the spring. *Any ideas?

I've seen small check valves for fuel systems and they run pretty low
pressure so the spring can't be all that big. But it will be an
experiment to see if the pump vacuum is enough to overcome any
spring. Got a vacuum meter you can put on the inlet? That would at
least tell you the draw.