Toto ST743S leaks when flushed

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rojasj

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Hi All,

I had to replace the fill valve on our Toto ST743S today as the original started to make howling noises which I suspect means it is on it's way out. Anyway, once I completed that project I noticed that upon each flush a drop of water would build up and occasionally leak from the bolts that hold the tank to the bowl )It's leaking from underneath the tank so I can run my hand on the outside and feel moisture). I assumed this has been happening since our plumber installed it a few years ago since I could see a tiny bit of rust on one of the washers. I first tightened the bolts down about 1/4 turn but that did not fix the issue. I decided to not tighten the bolts anymore as I could possibly crack the tank or bowl turning a small issue into a mess since we only have one bathroom.

I decided to simply spread some clear silicon on the around the metal washers to see if this stops the tiny leaks. My two questions are:

1. Was it ok to use the silicone or was it a bad idea?

2. What causes this? It's not a constant leak and only happens when I flush.
 

Reach4

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1. I doubt that it affected your leak.

2. That leak-during-flush would seem to imply that the water is coming from the big washer between the tank and the base. While I put silicone grease on mine, most people don't. It won't hurt. I tend to over-do some things intentionally where it won't hurt.

I would work toward tightening the bolts. The tank has 3 protrusions/bosses/legs that can meet the base porcelain to porcelain. You want to locate at least 2 of these. You won't be able to get to the one next to the wall. Apply side or corner pressure to the tank to create some separation, and slide a piece of copy paper in there. Tighten each bolt alternately until you can barely slide the paper into one place or the other. "16 pound" paper is about 0.00325 inches thick. http://www.casepaper.com/resources/calculators/paper-thickness-caliper/ If you had something thinner, that would be OK to use. Just make sure that you don't keep cranking once all three places touch. Being able to slide paper into one gives you margin.
 
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rojasj

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Hi Reach4,

Thanks for your reply and yes your fix would be the correct solution. I don't like the fact that I didn't really fix the issue, rather I used a band-aide on the problem by applying silicone to the outside of the washers. But this time around I figured it was the safest way to go about taking care of the issue. We only have one bathroom and if I broke either the tank or base while trying to fix the real problem I would have been in a bigger mess. Especially since I have never taken a toilet apart. It would have stunk if all of a sudden I had to run out and buy a new toilet and figure out how to install it. So, this time around I broke my own rule of using band-aide's rather than fixing the root of the problem. If I notice a leak develop elsewhere than it's time to fix it for good. If not, then I guess I will let the sleeping dog sleep.
 

Reach4

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Probably I made it sound harder than it is. At least wiggle the tank now to see how big of a gap you can detect to understand how much tightening is called for.
 

rojasj

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Hi, I just tried to wiggle it and it won't wiggle at all. I wonder if the bowl gasket needs replacement? It doesn't seem hard to replace at all. If I'm correct it looks like I just have to remove the two brass bolts between the tank and bowl as well as disconnect the water line (turn off the water of and flush course), pull off the tank, R&R the gasket and put it all back together again as well as use some silicone around everything.

I guess I'll keep an eye on things. If I see a drop of water elsewhere then it will be time for a real fix.
 

Reach4

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I used silicone grease-- not silicone glue or sealant. That lubricates and allows the gasket to spread evenly over the porcelain.

While things are apart, inspect for damages on and around the big washer.

I also used silicone grease on the 4 rubber washers on the bolts.

Your tank is not touching the wall, is it? That could cause a problem.

You might want to wait until somebody with more experience comes by before diving in. I think I have it right, but I have not actual had to deal with such a leak.
 

Gary Swart

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I would check that the big nut is tight. It will require large channel lock pliers. The leaking is not coming from the tank bolts, if there was a leak there, it would be constant. There is no pressure added when flushing to force water out around those bolts. Doubt the gasket is causing the problem, but if you pull the tank off, then replacing the gasket would be a simple and cheap enough thing to do. I'd also suggest you sand inside the tank over the bolt holes just to make sure there are no rough spots there.
 

Wallijonn

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I assumed this has been happening since our plumber installed it a few years ago since I could see a tiny bit of rust on one of the washers.

Usually the Spud washer. I replaced mine on one Drake (particulars in another thread) and coated the other Drake with Plumber's Pure Silicone Grease.
 

WJcandee

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Hi All,

I had to replace the fill valve on our Toto ST743S today as the original started to make howling noises which I suspect means it is on it's way out. Anyway, once I completed that project I noticed that upon each flush a drop of water would build up and occasionally leak from the bolts that hold the tank to the bowl )It's leaking from underneath the tank so I can run my hand on the outside and feel moisture). I assumed this has been happening since our plumber installed it a few years ago since I could see a tiny bit of rust on one of the washers. I first tightened the bolts down about 1/4 turn but that did not fix the issue. I decided to not tighten the bolts anymore as I could possibly crack the tank or bowl turning a small issue into a mess since we only have one bathroom.

I decided to simply spread some clear silicon on the around the metal washers to see if this stops the tiny leaks. My two questions are:

1. Was it ok to use the silicone or was it a bad idea?

2. What causes this? It's not a constant leak and only happens when I flush.

WHOA. I just read this and I have a question.

When you say you "could see a tiny bit of rust on one of the washers", do you mean the washers in the tank? Because one of the biggest leak-causing mistakes that handi-hacks (and apparently some plumbers) make is to not read the directions and to put the metal washer in the Toto tank (except on some Aquias). The metal washer doesn't go in the tank. Only the rubber one does.

It may be that you meant that you could see under the tank and that there was some rust there, but if you have metal washers in the tank, that's the source of your leak.

If tbat's the case, come back here and we will tell you how to reinstall the tank properly. And where to get a good new brass tank to bowl set. (Hint: Not at HD. I just tried to find one there the other day. Shudder.)
 
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