Leaking toilet tank mounting bolt — uneven tank walls/QC

[LarryLeveen]

Heya. New house to us has leaky tank. Bought replacement kit and installed per directions. Leak NOT FIXED! Flashlight and investigation shows the likely culprit — on one side, the nut is not making nice, even contact on the metal washer and providing even pressure on the rubber seals on the inside and outside of the tank (the nut is not cross-threaded). My guess is that the tank has some QC issues making the sides of the wall not parallel with each other. I don't want to crack the tank by overtightening the nut/bolt. What is the best thing to do here?

Is there a way to "face" the walls of the tank relative to each other? Should I just use a thicker and lower durometer outside rubber washer that will more quickly deform and fill up that gap? Is there such a thing as a wedge-shaped washer or spacer to help bring things into parallel?

As usual, thanks in advance.

 

[Jadnashua]

If the interior surface is rough, it can help to use some emery cloth to smooth it down some so that the rubber washer can seal better. Note that the interior of the tank should not have a metal washer...just the rubber one underneath the head of the bolt otherwise, water can leak out underneath the head of the bolt and the metal washer.

It can help to use a second nut to sandwich the bolt to the tank, and then a second set to hold the tank to the bowl. Not all tank designs will allow that but a thin nut usually will work and a full sized one sometimes.

You may need to have someone hold the tank while you tighten the bolts to help keep it vertical. You want to tighten the bolts evenly, so that means a turn or two on each side alternately. Many tanks have lugs or short legs, but you don't want them tight to the bowl as porcelain isn't really springy! I tend to slip a sheet of paper underneath those, and tighten until it has a little drag when trying to pull it out while not tearing or getting stuck. Make sure that the big gasket is installed evenly on the bottom of the tank for the tank/bowl seal. Some of them have a lip, and must be fully seated to mate up properly.

 

[Sponsor]

 

[LarryLeveen]

If the interior surface is rough, it can help to use some emery cloth to smooth it down some so that the rubber washer can seal better. Note that the interior of the tank should not have a metal washer...just the rubber one underneath the head of the bolt otherwise, water can leak out underneath the head of the bolt and the metal washer.

It can help to use a second nut to sandwich the bolt to the tank, and then a second set to hold the tank to the bowl. Not all tank designs will allow that but a thin nut usually will work and a full sized one sometimes.

You may need to have someone hold the tank while you tighten the bolts to help keep it vertical. You want to tighten the bolts evenly, so that means a turn or two on each side alternately. Many tanks have lugs or short legs, but you don't want them tight to the bowl as porcelain isn't really springy! I tend to slip a sheet of paper underneath those, and tighten until it has a little drag when trying to pull it out while not tearing or getting stuck. Make sure that the big gasket is installed evenly on the bottom of the tank for the tank/bowl seal. Some of them have a lip, and must be fully seated to mate up properly.

Interesting. Our kit came with enough metal washers to put under all nuts AND the bold heads so I used them all. I figured that would help distribute the force on the rubber washers more, but I think I see that you are advising that the bolt head actually bite directly into the rubber washer to make a seal, right?

I do have a recollection about the smooth finish being irregular somewhere but that might have been on the back (non-show) side of the tank and lid. I'll check the floor of the tank inside and out.

I'm definitely not reefing down on the lower nuts that mount the tank because the porcelain is not well supported there. As I thought about it though, the upper nut, which is just sandwiching the porcelain floor of the tank probably CAN be tightened significantly more because it is squeezing the porcelain and not trying to flex it like the lower nuts. I mean, I'll check and prep the tank bottom if it needs some smoothing, but even smooth, non-parallel tank wall surfaces will make for a challenging seal situation. Ideally, they would be smooth AND perfectly parallel so as the hardware is mating up with them flat. In the bicycle world, we call that facing and it is important in crank and steering bearings so we machine the ends of those frame tubes*. Maybe with just some imprecise handwork and an emery cloth, I can improve the fit.

* Some crank bearings are sleeved and held in perfect parallel and do not need faced frame surfaces. It weighs more, but cuts on manufacturing costs.

 

[Jeff H Young]

metal washer on the brass bolt head not helping anything . yes the nuts can be tightened as the porcelan wont be trying to flex and break . we dont need a perfect world with thick rubber gaskets , it should be apparant with a second look the problem . Pull tank and remove those washers inspect and reassemble

 

[Jadnashua]

Think about the washer in the tank this way...the metal-metal of the bolt/metal washer won't be water tight...that would allow water between the two to get to the shaft of the bolt, and leak out.

When you just have the rubber washer underneath the head, you're making a seal not only between the bolt and the washer, but the washer and the tank surface.

IN some special applications, a bolt-washer can make a seal (like in an oil pan drain), but the washer tends to be malleable, or crushable, to conform to make the seal.

 

[Jeff H Young]

no metal washers on top