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I've read variations on what hardware to use in bolting the toilet tank to the bowl. From a top down sequence with optional/variation items indicated in parentheses:

bolt

(metal washer)

rubber washer

tank

(rubber washer)

(metal washer)

(nut)

bowl

(rubber washer)

metal washer

[wing]nut

Observations:

  1. metal washer under bolt head seems discouraged due to possible leaks, but some feel it will provide more even pressure on the rubber washer
  2. some avoid anything (nut, washers) between the tank and bowl, perhaps to avoid clearance issues between the tank and bowl; this means the lower nut is both providing the pressure for the seal in the tank and securing it to the bowl
  3. the rubber washer under the bowl seems optional, maybe to help mitigate overtightening/cracking the bowl

Comments?

What sequence is recommended?

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6 Answers 6

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What sequence is recommended?

The one that comes with the tank when you buy it...

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  • Most won't have the instructions for the tank, especially if it's the home's original one. Or did you mean the instructions of a repair kit?
    – adatum
    Nov 16, 2017 at 17:14
  • @adatum - huh? Either you've dismantled an existing toilet, in which case put it back the way you found it; or you've bought a new one, in which case follow the instructions. Or have you somehow found a toilet tank and a separate toilet pan, with no connecting bolts, and you've decided to go buy yourself some bolts in order to connect them???
    – AndyT
    Nov 16, 2017 at 17:19
  • Or the tank has been previously repaired and people don't necessarily follow instructions? Anyways, this is irrelevant. There's no guarantee that the original method is the best method.
    – adatum
    Nov 17, 2017 at 3:26
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The proper way is:

  1. Put the rubber washer on the bolt
  2. Put the tank on the toilet base
  3. Put bolt through tank and toilet base
  4. Put metal washer on bolt and then screw on nut
  5. Tighten accordingly
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I say that the rubber washers should fit very tightly around the shank of the bolt. With this, when pressure is applied to the bolt pulling the tank down against the bowl, this downward pressure will squeeze and press the washer not only against the bottom of the tank to eliminate leaks but also around the shaft of the bolt. This is my story and I'm sticking with it.

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    I don't see how it's possible to have the rubber washer seal tightly against the shank of the bolt, since it's threaded. I see this as a reason to avoid the metal washer: the seal is between the tank and the rubber washer, and also between the bolt head and the rubber washer, making a complete seal. A metal washer under the bolt head means there's an interface not sealed by rubber.
    – adatum
    Nov 16, 2017 at 7:03
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    The metal washer will help distribute the force from the bolt, I usually add a dab of silicone calking on the inside of the rubber washer to tank I have never had a leak using this method.
    – Ed Beal
    Dec 16, 2017 at 21:51
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All rubber washers are always used closest to where water could possibly leak out. Metal washers back them up for strength in sealing.

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I've never seen a nut between the tank and the bowl. Seems like this could interfere with the seal of a thinner tank-to-bowl gasket as well. I have seen installations where rubber washers are stacked in between.

I have seen installations with metal washers under the bolt head and the nut, as well as without. I don't think it's useful under standard tank-to-bowl bolts, because they already have such large heads. If you are improvising with hardware on hand and lack a wide-headed fastener, it's probably necessary to get a good seal. Pretty much always see them under the nut.

Metal washer under the bolt head shouldn't have a leak if bolts are properly tightened - metal-to-metal seals fine when properly tightened, just look at flare and compression fittings.

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Based on nothing but "never having leaks" I do:

Bolt -> metal washer -> rubber washer -> tank -> nut

This lets me tighten the tank washer to prevent leaks without squashing the tank <-> bowl gasket too much.

On the bottom side I do bowl -> rubber washer -> metal washer -> nut.

The rubber is just to keep from cracking the porcelain. I don't like metal on porcelain. It seems to be "looking for trouble"

This doesn't have the official blessing of anybody, but it works.

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  • The rubber is for preventing water from leaking out, not to separate the metal from porcelain.
    – HazardousGlitch
    Oct 1, 2019 at 11:22

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