Backflow on shut down ?

[CharlieVT]

This is my first year with a dolly RO. Used, factory reconditioned.
When I turn it off, it backflows through the primary pump back into the feed line.
The pump runs backwards noisily while the back pressure comes off. It is a fluid o tech rotary vane pump; I'm worried it may damage the pump, it is quite noisy.
Is this normal?

[Bricklayer]

I had the same problem. I'm not running a MES dolly though. I installed a flapper style check valve right above my feed pump outlet. . Wasn't sure if I could install on on the inlet of the pump. If it ever failed it would burn the pump out so I didn't take a chance. And it stopped that problem. Try contacting MES. They are awesome to deal with. I'm sure they will help you out.

[Wizbi]

Why not elevate the hose end so that a reverse siphon can't occur?

[CharlieVT]

Thanks for the replies so far.
It isn't a syphon effect, it is a back pressure flow that starts fast on shutting off the pump and then slows to a stop.
When the pump is shut off, the backpressure runs the pump backwards pretty fast for a short period. It is pretty noisy and I wonder if it is bad for the pump. I had an early pump failure and don't want it to happen again.

I have talked to representative, who said he'd look into it and get back to me, I just thought I'd check here and see if others have experienced this kind of backflow with their ROs. I don't know yet what is normal and what isn't...

I have thought about putting a check valve at the pump input but want more info first but want to rule out other problems first.