Using a sealant to stop a toilet tank leak

Question

The toilet tank is leaking through the bolts, but the bolts are so rusted I can't remove them. I can't afford a plumber right now, but would like to stop using bucket-fulls of water to flush. My husband wants to use a sealant to stop the leaking. Is this feasible?

Answer 1

You can cut the bolts off with a mini hacksaw. The rubber washers inside the tank are shot, and that's what's causing your leak. You can fix it for $10.

1. Turn off water (I think you're already here).
2. Flush and sop up the remaining water in the tank with a sponge (or use a shop vac if you have one).
3. Cut off the bolts and remove them.
4. Replace with new bolts and washers.
5. Refill tank and check for leaks.

Mini hacksaw: https://www.harborfreight.com/6-inch-mini-hacksaw-65341.html

Tank bolts: https://www.lowes.com/pd/Keeney-2-Pack-Bolts/1001094052

Answer 2

Ultimately, the "correct" way to fix this is a new bolt kit, with stainless bolts and new sealing washers. Most hardware stores or big box stores will carry bolt kits for all major brands of toilets, plus generic kits. The kits include new bolts, nuts, washers, and rubber sealing washers, which are the part that's likely causing your leak. Write down the make of your toilet and snap a few pics of the bolts to bring with you to the hardware store to make sure you get the right parts.

Old rusted bolts are usually very weak. It's usually fairly easy to just snap the heads off them with a big enough wrench or pair of pliers or vice grips. The only potential issue with doing this is you need to be careful to not put pressure on the porcelain, as it's fairly brittle.

Once the old bolts are out, it's somewhat trivial to put the new parts in, and there are plenty of youtube videos showing the process if it's not obvious. Again, the only real caveat is making sure you don't really over-tighten the bolts and put stress on the porcelain.

Replacing the bolts is preferable to trying sealant for a few reasons. Applying sealant may prove harder than it sounds, since the parts really need to be very clean and dry for the silicone to stick well. And if the bolts are rusted, getting a good stable clean surface is going to be challenging. Plus, there's the potential for down the road issues. If the fitting gets gunked up with silicone, and someone does decide to actually apply a correct fix, you're going to be making their life very difficult.

When people ask "how do I do X" I don't like to generally say "do Y instead" unless it's easy to justify, but in this case, I think it is. Replacing the bolts may be easier than getting a good leak-free seal with sealant, and it will be about the same cost to buy the bolt kit as it would be to buy a tube of silicone. Plus, it's pretty much guaranteed to work and won't cause headaches down the road.

Answer 3

Billy Mays here for Flex Seal.

Answer 4

Rather than using silicone as suggested by Michael Karas, I would use something like Fernox LS-X which is actually designed as a leak sealant. In particular, it does not need to be applied to a dry substrate. If you empty the cistern and apply from the inside, you don't even need to wait for it to set.

Answer 5

A sealant like silicone would work as a temporary fix but there are some things to consider:

1. The silicone would need to be spread fully across the bolt heads and onto the adjacent porcelain on the inside of the water closet (tank). Thick layer over the rusty bolt heads would be a must.
2. The whole area where you apply the silicone will have to be clean and very dry. The silicone will not adhere well to wet surfaces.
3. You would need to apply the patch over the whole bolt head all in one go. A secondary application of the silicone will not adhere well to a cured first layer.
4. Make sure to let the silicone material fully cure before trying to put the water closet back into service.
5. Removal of the silicone from any surfaces that it decides to really stick to can be a pain to get it all off. This would be especially true for many toilet tanks that do not have a fully glazed interior.

When you are eventually able to address getting this repaired properly do endeavor to use stainless steel bolts to avoid the rust problem in the future.

Answer 6

If you are looking to use a product under water then you can try a wet patch for roofs.

https://www.homedepot.com/p/Henry-10-1-oz-209XR-Elastomeric-Sealant-HE209004/100001308

Answer 7

I'm really surprised nobody has mentioned the truly superior product here: plumber's putty. It's easy to remove, doesn't crack, and you can mold it around your bolt, where the rubber gasket used to go.

The one place you can't use it would be a custom gasket that covers all the bolts (some newer toilets use them). In those cases, the gaskets perform a leveling function on the tank as well. You'll have to buy a new gasket for those no matter what.

Answer 8

Everything Michael said is a must. I would think about using a few PVC caps for the patch. See photo below. You'd have to rough up the outside, inside and bottom with some sandpaper so the silicone adheres to the caps. Apply a ring of caulk around the bolt areas and also around the bottom of the caps. Then just press the caps over the bolts and let it fully cure.

Just a thought. By the time you do all this and wait 24 hours+ for the caulk to cure, you could hacksaw off the bolts and replace them and be done with it.. either way, good luck.