Pentair Minimax 400 Flange bolts rusted


Feb 4, 2018
Walnut Creek/CA
Have a Pentair MiniMax 400 heater for 20 years. It still works but we hardly use it for the pool because we have solar. Now, I have a small water leak on the outside large water flange and the bolts are rusted. It’s where the two water pipes go in and out of the heater.
I’m afraid to try and loosen it for fear of braking the bolt, then what? Anybody have any ideas to removing/softening the rust prior to trying to remove the bolt?


TFP Expert
In The Industry
Jul 6, 2011
You could try to spray it down with some WD40 or similar. If you break it, then you'll be down for a while trying to get it out and if you can't then your stuck.

Usually they are frozen and you can't get them out or they snap off. Either way, you sort of in a tight spot.