We've replaced several of these old style PF cartridges previously with no problems.

Changed one recently and when applying the 5 bolt flange and stem assembly, developed a leak at the front oring. It's about 2". So now I have a leak on the valve body.

Replaced front 2" oring twice, still leaks, just when shower valve is open.

Inner cast housing is brass or bronze and is smooth and clean with no burrs.

I'm certain that the replacement oring is correct. It's a number 131 and supplied by PF. Yet it leaks. Oring is the correct thickness.

5 flange bolts are pulled down evenly. Leaks with or without lube.

Short of replacing the otherwise perfect shower valve, what can be done to stop this new leak



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What is the model number? The only 5 bolt PP valve I know, the Flowmatic, uses a cork gasket, not "O" rings.



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No numbers apparent on these.
Supply house just matched up the parts.
It's about 25 years old based on the house age.
It's definitely a 5 bolt flange and definitely a #131 pp oring.

The outer hub of the valve is 4 bolt, but the round metal flange ring which secures it has 5 bolts.



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Cracked cartridge?

Tried 2 new cartridges. Both leak the same.
No apparent cracks.
With old oring it leaks a lot. With new oring it leaks less.

Need some pictures.

Fixed.

A last resort trick I've tried rarely over the last 40 years.

When caught far from a supply house with a defective oring, I've tightly wrapped them with 1 layer of Teflon tape. I did a half overlap of the tape around the full circumference of the oring. Installed it, no leaks.

The practical effect is to enlarge the oring cross section by a thousandth or two.



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