SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

I would say you've done everything you can to salvage that valve. Keep in mind, you're attempting to salvage a valve that 95% of irrigation professionals would rip out of the ground. I, personally, repair hundreds of Flo-Pros per year and replace twice as many. Don't stick anymore money into those pieces of junk.

I have minimal experience with he Flo-Pro. I haven't even seen one in what could be 15 years. They do stand out in my mind though. The word CRAP comes to mind.
I feel fortunate that they weren't installed more in my area.

My only input is, if it's leaking around the solenoid, check to see if there's a missing O-Ring. When that doesn't work change ALL the valves.

I'll put it in perspective...
Customer had a 12 zone system installed about 14-16 years ago (city water) and had flawless service of the valves for approx. 10-12 of those years (aside from the notorious winterizing problems). 2 years ago, they started having the common issues, flooded valve boxes, valves not opening, valves not closing, loose caps, etc. I informed them of the issues, the remedies, and the fix all solution. They opted for the cheaper diaphragm replacement surgery at that time. Well, the spring start-up this year (2 years after diaphragm replacement) brings more of the same. Loose caps, stuck valves, weeping valves, flooded boxes. I, again, quote total valve replacement with the Irritrol 2400T-B. I've visited this property 4 times this season to repair individual problematic Flo-Pros. They currently have invoices that amt. to half of what I quoted for total valve replacement. They are good for business!
Expect 2 years of reliable service before a repaired Flo-Pro causes issues again.

They do sound like money makers. There's one thing that bugs me though. I have an issue with fixing the same thing over n over again.
I've been having a problem with top of the line Superior brass valve adapters. The diaphragms are going bad in about a year.
Not all of them of course but way too many. The strange thing is it's always the same two houses who have the most problems with them.
The diaphragms bubble up and block the port.
Of course when I take a stack of diaphragms back to Ewing they didn't know anything about a warranty.
I know there is one. It used to say lifetime warranty. I can't find that anymore on the new site.
I read it on the Superior website. Which is now BucknerSuperior.com or something.
I never did get them replaced but that's a whole nother story about poor service.
I've been favoring the plastic Irritrol's over the brass lately.

Always inform the customer on the cheap fix and the right fix. Never get's old hearing "You were right" 2 years down the line. But, It's their money, and many can't afford the right fix, even though it makes financial sense.
Water quality has a lot to do with failing diaphragms. It doesn't sound like that's the problem in your case, though. Sounds more like poor rubber in the diaphragm. Perhaps water velocity is speeding up the degredation of the rubber.?
I know Toro makes 2 replacement diaphragms for the Flo-Pro. The original version, and one that is a little beefier with different chemical makeup. Neither lasts as long as the original diaphragm.
We've got a handful of sites with 2" Rainbird Brass valves from the 70's, and generally replace one diaphragm per year. I've never installed a brass valve since I've never run into pressures that warrant such a valve. Irritrol's valves work extremely well even in 100+ psi systems. The 2400 and 216B are extremely dependable. Some selonoid issues a year or so ago, but they seem to have remedied that.
Hopefully your suppliers will grow a pair and stand by what they sell. A lot to ask when money is leaving their registers.