Toilet Tank Leaking Around Bolt

Ever since I installed a Universal-Rundle tall commode 10 years ago, I've had a recurring problem with a very small leak around the right mounting bolt which securs the tank to the bowl. I've had to retighten the bolt at least every year. The left one has never leaked.
Last week I removed the toilet so I could put down new vinyl tile flooring. While it was out, I bought a new tank mounting kit at Lowes....big donut center gasket, two new long bolts, two nuts and four each rubber or fabric washer and flat metal washers. I thought for sure the new mounting hardware would fix the problem. However, after reinstalling the commode there's STILL a small leak around just the right bolt. Tried backing off the other bolt and retightening the right one...no luck.
I drained, dried and carefully inspected the insides of the tank. I noticed there are 1/32 to 1/16" raised letters in the porcelain which say MADE IN USA in the bottom. Unfortunatele, part of the 'M' and the 'A' letters are so close to the right hole that the rubber washer has to fit over them. I'm thinking they create just enough of an obstruction that the the washer will not seal in that area. What I'd like to know from you plumbing-savy types is the following:
1. Can I file or sand the raised letters off the porcelain without harming its waterproofing ability?
2. If sanding porcelain could be problematic, I'm considering putting a small amount of either plumber's putty, pipe joint compound (aka pipe dope) or silicone caulk/adhesive between the rubber washer and the letters to try to seal the small leak. Which of those products would hold up best under water without harming the washer?
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100% silicone would seal it, clear would be the least noticeable. I once sealed a big aquarium with the water and critters still inside. It cracked as we watched one evening, right across the front. i got a small tube of GE silicone seal and rubbed it into the crack fron the outside and it stopped leaking. It was still holding water that way for a well over a year, & would have indefinitely, but I bought a bigger tank. I turned it around at the next cleaning so the crack would face the wall, & used a background in front of it
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I 2nd the silicone. After all, fish tank joints are assembled totally with silicone. Make sure tank is dry. Hit it with a hair dryer right before assembling and sealing. Let it sit min 24 hrs after.
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Red Green wrote:

another, more messy option would be Permatex No. 2 if the silicone fails. It will only clean off with alcohol.
nate
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A leak is usualy a bad wax ring, replace it.
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On Fri, 7 Aug 2009 14:11:39 -0700 (PDT), ransley

OP is talking about the tank a bolt leaking.
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I would try the plumbers putty first. It stays soft and if you ever have to remove it, it is a lot easier to deal with than silicone or caulk.
Make yourself a little doughnut from the putty stick it on the tank and then assemble. The excess will ooze out and you can just pick it up by hand.
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SILICONE IS THE ONLY WAY! I silicone everything like this! the FIRST TIME1
Its easy to remove if needed cheap and works great!
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bob haller wrote:

...
Well, it'll work but plumbers putty is the more appropriate product for the purpose.
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Odds are a common angle grinder with a $6 Harbor Freight diamond blade wold gently remove the raised letters with no stress to the porcelain. The trick is to avoid a tool/cutter set up that impacts (hammers on) the substrate. Some practice on a piece of window glass would give an idea of the technique. Dremel makes similar things that would work.
Joe
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wrote: Odds are a common angle grinder with a $6 Harbor Freight diamond blade wold gently remove the raised letters with no stress to the porcelain. The trick is to avoid a tool/cutter set up that impacts (hammers on) the substrate. Some practice on a piece of window glass would give an idea of the technique. Dremel makes similar things that would work.
Upside you save on plumbers putty,
downside you have to replace the tank.
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Rubber washer/metal washer/nut sandwich around the tank part.
From the inside of the tank assemble the following: Bolt head Metal washer Rubber/fiber washer Tank porcelain Rubber/fiber washer Metal washer Nut <--- tighten this nut independently to get a good seal around the tank hole independent of the connection to the bowl. This allows you to tighten down without leveraging and cracking the porcelain bowl Bowl porcelain Rubber/fiber washer Metal washer Nut <--- tighten this to secure tank to bowl and prevent leaking from the drain tank drain seal. Also to confirm whether leak is coming from bolt hole in tank or from seal with bowl do the following: - If it leaks all the time, it is leaking from the tank (either the bolt hole, a crack in the porcelain, or aound the drain gasket) - If it leaks only when you flush, then the tank may not be seating tightly against the bowl.

Adding some pipe dope around the bolt and washers in the first sandwich can help if still leaking.
Entombing with silicon is to me a last resort and a sign of a kludgey-DIY repair.
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Just apply a bunch of silicone to the bottom of the rubber gasket and over the bolt head after its tight. DRY EVERYTHING FIRST.
On Fri, 7 Aug 2009 09:21:33 -0700 (PDT), Josh

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