I have tried two new water supply hoses on my toilet tank. Each time they have leaked at the tank. I was very careful to, at first hand tighten and then, gently, with a channel lock pliers, turn them a little bit more. They leaked regardless. Of course, they had perfectly good looking tapered rubber seals inside. They are the standard stuff you buy at Home Depot. Can the answer to the problem only be that the threaded plastic inlet pipe is somehow defective?

  • Welcome to Home Improvement. If you'll please edit your question to include some pics of your inlet pipe threads and the threads of the hose you're connecting, that will help with the diagnosis. Generally, though, hand-tight is sufficient, so damaged threads are a distinct possibility. Damage could come from having been over tightened previously, is that why you're replacing the supply line in the first place?
    – FreeMan
    Commented Jul 14, 2020 at 16:20
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    Sometimes it is the fill valve tank connection that is leaking and running down onto the hose making it look like the hose is leaking when in fact it is not.
    – Alaska Man
    Commented Jul 14, 2020 at 16:40
  • I have purchased new supply lines ("the standard stuff you buy at Home Depot") that have leaked where the hose was compressed to the fitting.
    – Alaska Man
    Commented Jul 14, 2020 at 17:30

1 Answer 1


To answer your question could the plastic threaded inlet be the problem , possibly. That pipe could be cracked or the seal in between the fill valve and the tank could be leaking. This is a tough location to get a good look. Normally I find them over tightened but it sounds like you have been careful.

I might turn the water off drain the tank and hold the float up,

no water dripping turn the water on see if it starts dripping float still up, this would indicate a crack in the plastic and a need to replace the fill valve.

If it doesn’t drip but starts once a few inches Of water are in the tank drain again pull the fill valve and use a little silicone calking on the seal tighten it back in place let it sit for 15 minutes or longer to set, then try filling again it may have been a leak that you just sealed with the silicone.

At this point if it still drips look for hair line cracks in the tank itself.

Those are the things I normally check quite often I have found cracked plastic fittings after being over tightened.

  • The leak is definitely coming from the nut on the supply line. There is no water coming from above. Sorry, I did not make that clear enough.
    – plumbob
    Commented Jul 14, 2020 at 17:06
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    It could be cracked under the threads of the supply line . I tried to provide All the failures I have seen in the past.
    – Ed Beal
    Commented Jul 14, 2020 at 17:54
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    A cracked plastic fill valve fitting can suddenly fail catastrophically. If you are not home, then you will have a flood. Get a new fill valve. Commented Jul 14, 2020 at 18:47
  • Turns out it is a cracked fill pipe and I have been certain to replace it.
    – plumbob
    Commented Jul 16, 2020 at 1:12
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    I believe if you read my answer I pointed this out 2x and in the comments.
    – Ed Beal
    Commented Jul 16, 2020 at 3:03

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