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?

  • 19
    To me, the (obvious?) choice seems to be: get a new bolt kit. The new bolts will come with new sealing washers, which will stop the leak. It would probably cost the same as a tube of silicone, but it would be a more "as designed" type of fix. Rusty bolts are usually easy to just snap off with a big enough wrench. Just need to be careful not to crack the porcelain. Is there a reason you're hesitant to go this route? I didn't want to suggest this in an answer if there's something stopping you from considering it.
    – dwizum
    Commented Nov 18, 2019 at 16:28
  • @dwizum Obvious to those of us not afraid to perform that task. I think it is quite evident that OP is not comfortable; hence the plumber cost dilemma.
    – MonkeyZeus
    Commented Nov 18, 2019 at 20:27
  • 8
    I guess I see it as a catch-22. The chances of someone not experienced with plumbing being able to get the fitting clean and dry enough for silicone to stick, and then applying it in a way that actually seals the leak, seems pretty slim. I don't really see that as "easier" or less involved than just doing the job right.
    – dwizum
    Commented Nov 18, 2019 at 20:39
  • @dwizum Not sure how long they've been flushing the toilet with a bucket of water but the tank could very well be dry by now.
    – MonkeyZeus
    Commented Nov 18, 2019 at 20:54
  • I would try to get this fixed as soon as possible. When I had this problem, the bolts rusted all the way through and broke, and I ended up with an inch of water on the floor (thank goodness I found it so soon). Commented Nov 19, 2019 at 1:16

8 Answers 8


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

  • 5
    An additional resource for removing the bolts is this question - diy.stackexchange.com/questions/14084/… . It describes several methods to remove rusted tank bolts and precautions to not crack the tank. Jared has provided the correct solution to REPAIR the problem and not merely patch it or fix it.
    – Freiheit
    Commented Nov 19, 2019 at 14:25
  • 1
    I've never had to cut a tank bolt, probably because I have a flathead screwdriver large enough to be used as a baseball bat.
    – Mazura
    Commented Nov 20, 2019 at 1:40
  • 1
    Another variation to remove bolts: if you don’t have the clearance to use even the mini-hacksaw, take a new hacksaw blade and wrap a scrap of cloth the size of your handgrip around one end. Secure with several layers of duct tape and slip the blade between the base of the toilet and the floor. Saw until bolt breaks free. Replace not only the bolts but the wax ring as well. Once that seal is broken, it should be replaced.
    – M.Mat
    Commented Nov 20, 2019 at 4:31
  • The tank bolts I am familiar with have the bolt head on the inside of the tank and on the outside (bottom face) of the toilet, the nut. There is not an obvious place to cut a rust-damaged bolt (one that cannot have the nut removed) that would separate the tank from the bottom half as far as I can tell. Seemingly no room to stick a hacksaw blade into. Could you perhaps amend the answer to indicate where exactly you suggest the bolts be cut to better illustrate?
    – Sander
    Commented Nov 20, 2019 at 9:51
  • Didn't see this when I posted my similar answer. Although I agree with commenters, it's a little tricky to get a hacksaw blade in to or under a toilet to actually cut the nuts or bolts. I've never had to actually cut a tank bolt though, usually by the point a bolt is rusted enough to leak, it has lost all structural integrity and it pretty much crumbles apart under very moderate pressure from a wrench or pair of pliers. Or if it's just a little rusted, the rust is usually only on the head of the bolt inside the tank, and you can grab it well enough with pliers to spin the (not rusted) nut off.
    – dwizum
    Commented Nov 20, 2019 at 15:30

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.

  • 2
    Using silicone is clearly a bad idea. What about a dedicated link sealant that doesn't need a clean or dry base to adhere well? Commented Nov 19, 2019 at 14:58
  • 1
    @MartinBonnersupportsMonica it still requires cleanup when it eventually gets done the right way.
    – rtaft
    Commented Nov 19, 2019 at 15:06

Billy Mays here for Flex Seal.

enter image description here

  • 1
    I was going to mention their spray on rubber sealant: flexsealproducts.com Commented Nov 18, 2019 at 19:27
  • 5
    I would not recommend this. I get at best a year before this stuff starts to crack and peel in outdoor conditions.
    – rtaft
    Commented Nov 19, 2019 at 15:03
  • 4
    @rtaft. While your point is 100% valid, is your toilet outdoors? Commented Nov 19, 2019 at 18:03
  • @MadPhysicist It would probably work better given the temperature range does not fluctuate as much, though it does change temperature very quickly from room temp to ground water temp. I don't know that it would hold up any better.
    – rtaft
    Commented Nov 19, 2019 at 18:24
  • @rtaft UV exposure indoors is dramatically less. Also, temperatures indoors usually stay above freezing (that may also be true outside in your location). Commented Nov 20, 2019 at 10:46

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.

  • 3
    LS-X is to plumbing, what WD40 is to lubrication. Counsel of perfection says to completely re-do whatever is leaky. But LS-X fixes it well enough 99.something percent of the time.
    – nigel222
    Commented Nov 19, 2019 at 11:18
  • Normally Fernox LS-X is put in the joint before doing it up, not over the top of a leak.
    – Walker
    Commented Nov 20, 2019 at 17:53
  • @Walker It can be (although Fernox sell Hawkwhite specifically for that purpose), but it can be used also be used directly to seal a small leak (obviously it's not going to work if someone has broken a six inch hole in the cistern). Commented Nov 20, 2019 at 21:14

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.


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

enter image description here


  • 1
    Selley's "All Clear" sealant is another option, or any kind of "fish tank repair" sealant.
    – Jasen
    Commented Nov 19, 2019 at 7:41
  • @Jasen Good call about fish tank sealant but I am not sure if OP lives in Australia for the Selley's product.
    – MonkeyZeus
    Commented Nov 19, 2019 at 14:49

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.

  • I thought about that. It might work well if you were able to jam it into the leak itself, it's relatively cheap and very easy to remove when you go to replace the bolts. I doubt it would work just by covering the entire bolt, you'd need to really work the stuff in.
    – rtaft
    Commented Nov 20, 2019 at 14:03
  • @rtaft I would recommend re-mounting the tank if you do. I watched my uncle do this many years ago and that's how he handled it. Just plastering it from the outside may not work.
    – Machavity
    Commented Nov 20, 2019 at 14:05

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.

enter image description here

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.

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