[Shop-talk] Sealing toilet tank mounting bolts?

[Jim Franklin]

I bought 3 Kohler Cimarron toilets for a job I'm doing, because the one in my house is great. Well, the new ones are very different and I should have read all the reviews on the Home Depot site.

The tank-to-bowl connection is made with 2 bolts that pass through grommets. These grommets expand as the bolts are tightened, sealing the holes in the tank through which they pass. Problem is, quality control let some tanks through with holes oversize enough that the grommets won't seal. Kohler even sent me a new supposedly redesigned grommet kit, which slowed down the leaks to a drip once per minute. They said they'd send a new tank but can't expedite it, so we're looking at after Thanksgiving, and no guarantee that the new tank won't also be mismanufactured.

My thought is to use a sealant on the grommets. Kohler said "we don't advise that", but I really need to wrap this up. Is there a rubber-compatible, submergeable sealant that will work in this application?

Another thought I just had is to add washers on top of the bowl where the bottom of the grommets sit so that the grommets are compressed another 1/16". But I don't want the grommets to then start leaking on the inside along the bolt if I overcompress and they open up. 

There are images near the bottom of this page:

https://www.faucet.com/kohler-k-31615-white-cimarron-1-28-gpf-toilet-tank-only-left-hand-lever/f4091621#reviews

thanks,
jim