Question about Bot Suction on Fiberglass Pool


New member
Apr 25, 2019
I have a new Trilogy Graviy rectangular fiberglass pool and our builder has been letting us test both the Pentair 930 (equivalent to Dolphin S300i?) and the Dolphin M400. Over the last 2 weeks neither has had any luck climbing the walls. We have a lip around most f the pool, but have seen videos of bots that climb these lips. We’ve also attempted to manually apply the bots to the walls and at best they stay for a few seconds before drifting off.

The walls are smooth, but have no film, algie, etc. the water has also ranged from 65-71 degrees, which is cold, but I’m not sure is to blame. I’ve also read a ton of forum posts for troubleshooting and have ensured the quick run settings are turned off, etc...

Have any owners out there had luck with particular models having better suction on fiberglass? Am I out of luck with a robot cleaner?



TFP Expert
Platinum Supporter
May 23, 2015
Tucson, AZ
Are these loaner units new or does this builder just have them fur demonstration purposes? Chances are if they’re old then the treads are worn out or the unit’s motor is a bit defective. These robots should have no issues climbing a fiberglass pool wall. My guess is there’s something defective about the units that he has loaned you.


Well-known member
Aug 19, 2013
The 930, like all robots in that family, don't adhere to the wall by suction, they divert water out of the top of the unit applying lateral force to keep the robot on the wall as the motorized treads move it up the wall. As mknauss pointed out, it doesn't matter whether the wall is fiberglass, plaster or vinyl, if the robot is working properly it will climb any wall.


Silver Supporter
Jun 20, 2018
Annapolis, MD
My Polaris 9550 has no problems climbing my Fiberglass pool walls and steps. When set on just water line cleaning, does a great job at that also. It even climbs up and onto my tanning ledge.


New member
Apr 25, 2019
Awesome. I’m feeling better. Just need to trust that the current bots are running less efficiently and will probably move forward with the pentair 930.

Thanks everyone.