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Toilet Leaks Between the Tank and the Bowl
When I flush the toilet, I noticed
that water seems to leak on the floor from between the tank and the bowl. How can I repair
This is symptomatic of a leak in the tank-to-bowl seal or around the
tank-to-bowl mounting bolts. Follow the
following steps for a quick and sure repair:
- Shut off the water to the toilet.
- Flush the toilet, and then sponge out the water remaining in the tank. Important:
Be sure to take out any bricks, bottles, small water craft, or fish that may remain in the
- Disconnect the inlet tube at the toilet, not at the shutoff. If you disconnect the tube
at the shutoff compression fitting, there is less of a chance that you will be able to
reuse the line later. Look at the line itself. If it is chromed and has a washer on the
top, you should try to get a replacement washer when you go to the hardware store. All
stores don't have them, so you may want to purchase a new supply tube while you are out.
Since there are a few different variations on the supply lines, see
How do I
install a new intake line to my toilet?
- Now comes the fun part. You must now unbolt the toilet tank from the toilet bowl.
If you look inside the toilet tank, you will see two very large slotted screw heads.
These go through the tank and the bowl, with a nut on the end under the toilet. You must
remove these screws. Sometimes they are easy, and sometimes not. If they do not budge at
all, you can drill the screw head out. Using an 1/8" or thereabouts bit, drill one
hole through the center of each screw, at least 1/4" in. This is your guide.
Go through your box of drill bits, increasing the size of the hole until the head of
the screw comes off. It's made of brass, so the drilling won't be difficult if your bits
are sharp! And, since you are working around porcelain, control your drill and be careful
not to damage the toilet.
- Lift the tank off of the bowl. You will see a disgusting mess of melted rubber and other
vile stuff... this was the tank-to-bowl seal! Peel it off the tank, put it in a bag, and
drive it over to the undertaker... I mean hardware store. Most hardware stores worth their
salt will offer a few different sizes of this seal, so it pays to have something to
compare them to. Plus, it gives you something to show off to the guys! Guys like this
- Hey, I didn't say to leave the hardware store yet! You also need to purchase a new
tank-to-bowl bolt kit. Even if you didn't have to drill out the old set, don't reuse it.
The new kit will supply you all the parts you need, and is designed to make it easier to
get a leakproof seal.
- The generic tank-to-bowl bolt kits I have used a specific order of assembly. Then are
different from the factory kits in that they have additional parts to get a better seal.
If you do not assemble them correctly, the seals between the tank and the bolt heads will
leak. A metal washer and a fiber washer are put on the bolt. Slide the bolt into the tank
holes from the inside. The fiber washer should be in contact with the inside of the tank.
There is a nut that must be secured to the bottom of the tank. This nut tightens the bolt
head against the inside of the tank, squeezing the fiber washer tightly to form a
- Place the new tank-to-bowl seal on the base of the flapper assembly
under the tank. If your water is heavily chlorinated, rubbing some
silicone plumber's grease onto the seal should increase its useful life.
Don't use Vaseline petroleum jelly... it may react with the rubber and
shorten its life!
- Position the tank over the bowl so that the bolts go through the holes in the bowl. Use
one fiber washer, one metal washer, and a nut (or in some cases a wing nut) and begin to
tighten the tank to the bowl. To prevent breakage of the tank, tighten the nuts a few
turns each, keeping even downward pressure on the tank-to-bowl seal.
- DO NOT ALLOW THE TANK BOLTS TO TURN WHEN TIGHTENING THE TANK-TO-BOWL NUTS! The bolt heads should be held stationery (using a screwdriver) when tightening the tank-to-bowl mounting nuts. Allowing the bolt head to turn may twist the washer under the bolt head, leading to a leak. (Note: If you are using a manufacturer replacement kit you may only have a single nut per bolt. It is even more important to do all the tightening at the nut, not the bolt, for the same reason... possible damage to the seal.)
- Check the orientation of the tank with respect to the intake line. If you are going to
reuse the old intake line, it should be close enough to the threads on the inlet valve to
begin threading the coupling nut. You can start threading the coupling nut, but do not
tighten it completely at this point.
- Continue to alternately tighten the nut onto the tank bolts until the bottom of the
toilet tank hits or nearly hits the toilet bowl. The tank should be very solidly placed.
Give it a little shake to see. No... the tank!
- Before turning on the water supply, pour a gallon of water into the tank to check for
leaks. Leaks around the bolts will show up immediately. It is helpful to use a flashlight
for this step. Now, flush the toilet and look for leaks around the tank-to-bowl seal.
- Finish tightening down the inlet valve coupling nut. Turn on the water slowly and
fill the tank and flush. No leaks? Good work!
- Siesta time! And not on the bathroom floor... get out
of there already!
You may ask... why should I replace the tank-to-bowl gasket when
the leak is from one of the bolts? Because I say so! If
the toilet is more than a few years old, the gasket has become somewhat
stiff. Disturbing it in any way (aside from loud noises... common in
many bathrooms) will almost definitely cause a leak. Why take the
chance... do it right the first time!!
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