installing flush valve

I had a toilet tank that needed a new flush valve, so I picked one up at Lowes, a universal plumb pak....no matter what I did, everytime I put the tank back on, a small leak happened around the nut of the flush valve on the bottom of the tank. I even filled it at the kitchen sink and watched to see if it would leak, but when installed, a few hours later it was leaking on the floor. I had another tank just like the first and put a new flush valve on it and lo and behold, a few hours later, it leaked also...for the life of me I really don't know what I was doing wrong. These were toilets in a mobile home...a 'oso' model(?) Don't know if I was tightening the nut too tight or didn't have it tight enough...any thoughts? I finally purchased a new tank and put it on, no problems, as of right now.
BTW...on the tank to bowl gasket, does the gasket have to fit over the threads and the nut? or just the threads only? thanks, Mike
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With that plastic nut on plastic threads of the valve, I use teflon tape on the threads so I can comfortably snug it up more than I would have been able to do otherwise. Never had one to leak. For all I know, the teflon tape may be having the secondary effect of sealing the leak instead of just letting me tighten it up.

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MikeL wrote:

In the first place you don't remove the tank to replace a flush valve.
--
LSMFT

Simple job, assist the assistant of the physicist.
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i use silicone seal on all the leak areas if i take the tank off......
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There should not be any leak areas. And feel free to give me your full name so that I can have a name to curse as the idiot that used silicone when good workmanship would have been adequate and appropriate.
BTW, a lot of people put the tank on wrong and cause their own problems.
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On Sat, 15 Jan 2011 19:16:36 -0800 (PST), Michael B

box is for, either. Or they don't know how to read or interpret the instructions printed on them. You wouldn't believe how many WRONG ways people can discover to install something as simple as a flush-contro valve kit!!
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well blame a pro plumber who I called, since i couldnt get the leak stopped. he siliconed it and charged me 150 bucks.
silicone seal comes off easy, so its no big problem
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you must be thinking of the 'fluidmaster' or the ballcock...no need to remove tank for that replacement
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If you are replacing the entire flush valve on an American Standard throne you DEFINITELY need to remove the tank, as the nut that holds it on is between the tank and the bowl. If you are only replacing the water control unit, or the flapper portion of the flush valve you can do it while assembled.
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Was it leaking from around the flush valve nut or the tank to bowl gasket? Was there a gasket on the flush valve (not the tank to bowl gasket but the other one) and did you install it and if so did you tighten the nut too tight to cause it to squeeze out from under the flush valve? Did you check the porcelain around the flush valve nut to make sure there were no nicks or cracks since porcelain isnt always cast perfectly? Did you slightly tilt the tank after installation that caused the tank to bowl gasket to bind which would leave a gap and cause a leak? Could the leak be coming from around the tank bolts and did you use a flashlight to make sure? Did you thoroughly clean the bolt threads so that they do not bind?
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In my opinion, this is not something that needs to be checked with a flashlight. Proper way of starting the process is to have the flapper valve installed, as well as the flush valve. Then it's time to put in the tank bolts. For each bolt, first a metal washer, then a rubber washer. The bolt goes through the hole. Then a rubber washer, and another metal one. Then the narrow nut that is included. This means that the two rubber washers can be tightened up seriously tight without being concerned about breaking the porcelain. And then the tank can be set on a couple of bricks and filled with water. And sit a while. If the flapper is going to leak, you can see that. If the fill valve is going to leak, you can see it. And if the bolts are going to leak, which is very unlikely, you can correct it.
If a person wanted to, they could carry the filled tank around before putting it into place.
Then set it into position, snug up the wing nuts onto the tank bolts after putting on the last metal washers and it's ready to be connected to the water supply after already knowing that it's not going to leak.
Doesn't everyone do it this way? As a matter of fact, no.
Too bad for them.
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On 1/15/2011 7:49 PM, MikeL wrote:

I'm picturing the big gasket under the big nut. Lots of situations like this tell you to put the paper gasket on top on the rubber gasket. The paper/cardboard gasket slips and keeps the nut from twisting the rubber gasket and making it leak. Not sure how well you can picture that, but if there was a shiny piece of paper the same size as the rubber gasket, put it on before the nut.
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