Polaris 3900 backup cycle time


New member
Mar 3, 2017
Been takin care of everything in a client's home for years. They canned their pool professional a few months ago - letting the kids do the work. I get the calls when the kids can't figure things out. The Polaris 3900 waS installed years ago given the collection of replaced parts laying around (bag, float etc). Was called in to deal with sweep not moving well - and found the chain had jumped. Replaced tensioner and added chain guard - and sweep is moving again. However, the backup frequency is suspect so I investigated pressure etc and found the following.
- No restrictor disk
- RPM at about 20
- 2 minutes run time and the 30 seconds backup.
DE filter but not sure if the pressure is low or high - so will be doing a backwash to see if this increases pressure/RPM on the sweep.

However, if I get the RPM's up 30%, then I suspect the backup valve cycle time will also speed up 30% - running 80 seconds and then 20 second backup? Clearly - not something that will work. Ideas?


Bronze Supporter
TFP Guide
Jul 24, 2015
Central Valley CA
Welcome to the forum :handwave:

I agree you should do the backwash first and see how it goes, sounds logical that the cycle time would increase with a higher volume but who knows. It could be the time for each mode may not be linear if the pressure utilized for each function fwd vs back is not equal as well. Hard to explain but comes down to it is free to do the backwash and see how it goes. If it does what you suspect I would say replace the backup valve, I don't think they are serviceable and at $25 to $50 for a new one on line not that big of an expense even if you could service it, you time is probably worth more than the part and the effort to fix it.