I had an issue with my bathroom flooding, so I emptied out the toilet (turned off the valve and flushed until it was empty).

Then after 2-3 days, the toilet backed up. Yech.

Anyway, I re-opened the valve, flushed, and cleaned the toilet, and I put newspaper underneath. I noticed now two leaks:

  • A widening wet spreading underneath the supply line for the toilet valve
  • A tiny drop-sized wet under the back of the toilet

My question is about the leaking pipe with the shut-off valve; how can or should I fix this? Should I call a professional, or is this DIY material?

Edit: There's a giant nut with two fins where the supply line connects to the toilet. It's wet. Very suspicious.

1 Answer 1


Knowing where the water lands gets you in the area, but what you really need to know is where the water came from. Is the tank cracked, is the supply line failing, is there a bad connection on either end of the supply line, or is the valve itself going.

If the tank is cracked, you'll have to buy a new one, and it's a large project if you're not used to working on basic plumbing jobs or are skirmish around an open toilet.

A bad supply line can be easily replaced and it's even easier if it's just the washers.

A bad valve may just have some dirt or buildup in it that will be fixed by opening and closing it once or twice with water running through it (an empty toilet tank). Though keep in mind any dirt may then get in the toilet valve and could cause it to run slowly until you clean it out. If that were to happen, just post another question. It could also be the packing material in the valve, which I've never touched on this type of valve. If that's the case, you may be able to minimize it by opening the valve all the way. If the valve is too far gone, you'll likely need a blow torch and solder to replace it. This can be a DIY job, but if you get in over your head, the water for the whole house will need to be shutoff until you can get a plumber out.

  • I've updated my question -- the connecting nut on the supply line at the toilet is very damp. That's very incriminating. Does that change your answer?
    – ashes999
    Apr 11, 2011 at 21:33
  • @ashes999: turn off the water, unscrew it, and then inspect for: damaged washer, cracked nut, cracked or damaged threads on the toilet tank. You can try replacing the washer. If that doesn't help, and there is nothing else obvious, you can try replacing the hose itself.
    – gregmac
    Apr 11, 2011 at 22:50
  • Hand tighten that nut. If it's still leaking, shutoff the water at the wall, drain the tank (long flush), and unscrew the line. You can try replacing the washer or the entire line (they're relatively cheap). With any connection on the toilet, I tend to do as much as I can by hand, and then maybe a quarter to a half turn by wrench.
    – BMitch
    Apr 11, 2011 at 22:51
  • It's also possible the valve in the toilet isn't screwed tight enough to the tank itself (this is the threaded part that is connecting to the supply line and is the tall part connected to the float in the toilet). Note that if you overtighten this to the tank itself, you can crack the tank.
    – BMitch
    Apr 11, 2011 at 22:53
  • I tried hand-tightening everything, and it seems very tight already -- didn't move. I'm going to replace the supply line.
    – ashes999
    Apr 12, 2011 at 17:00

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