Franke Sink Stopper - Leaky Seal Repair

We did a kitchen renovation about 10 years ago, and installed two side-by-side Franke stainless steel sinks. Total cost was substantial. Only three years after installation, the stoppers started leaking - if you filled the kitchen sink with water and walked away, it would be empty in about an hour. I did a bunch of research, and found that you could purchase a replacement rubber seal for the stopper, you could only purchase the entire stopper. Not particularly cost effective. 

Franke 1145 Strainer Assembly - Expensive way to replace the stopper seal

Note how the new seal on the stopper looks

So - I had a close look at the stopper and seal design, to try to determine why the stoppers were leaking. The seal is in the shape of a tee - with the base of the tee set into a groove on the stopper, and the sealing surface protruding perpendicularly from the base of the tee. When the stopper is set in place, the sealing surface is pushed laterally, and causes the base of the tee to rotate. If the seal rotates enough, you get metal to metal contact between the stopper and the drain fitting, and water can escape past the rotated seal. 

Left Stopper - normal seal. Right stopper - seal flipped down and leaking

I researched possible replacement seals - o-rings, or similar shaped seals and didn't find anything that would fit or seal. You can not purchase just the replacement seal from Franke - you can only purchase the entire replacement stopper. 

Seal removed from stopper - not available as a replacement part

Then, I figured maybe there's another way to prevent the failure mode - the rotation of the seal. What if I could add some support for the perpendicular sealing surface, prevent it from rotating. I found that a very small diameter o-ring stretched around the stopper, just above the seal, supports the seal and keeps it from rotating, and allows the sealing surface to do its job. I've had this fix now for over a year, and is completly reliable. 


Large o-rings, small cross section

Simple stretch the o-ring over top of the seal, snug it up against the metal body, and it will prevent the large stock seal from rotating and leaking water.

Look closely - note the o-ring avove the stock seal

Another view - O-ring above the stock seal
Works well. 

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