The hot water supply hose under my sink started leaking after I replaced the popup drain on the sink. Apparently I disturbed the hose in some way. It is leaking from just above the nut where it connects to the shutoff valve. I removed it and added new plumbers tape, and after reconnecting it was still weeping after I checked it 10 minutes later (about 1 drop). So I tried tightening it more, and it began leaking faster (again, from above the nut). Do I need to replace the hose itself? I'm thinking the gasket/washer, whatever it is, is just old. I have no idea how old this hose it, at least 10 years.
Over tightening a plumbing fixture can be just as bad as under-tightening, as it can damage the threads and prevent a proper seal.
In your case, you should try to fix this first by reconnecting the pipe with a cleaned fitting:
- Remove the hose.
- Remove the existing tape completely.
- Clean the threads on the hose and the fitting with a wire brush.
- Wrap new silicon plumbers tape around the threads TWICE - no more - too much is not a good thing. This tape isn't to create a seal, it's to ease the turning of the nut.
- Reconnect until the hose fitting is snug. DO NOT over tighten as this promotes leaking.
If this doesn't work, disconnect the hose and replace with a new wire mesh hose, using the same taping method.
Does flexible = plastic or flexible = braided hose with permanent nut fittings on the ends?
If this is one of those braided type hoses with permanently attached fittings on each end, then they seal with a rubber gasket permanently installed in the nut fitting. The hose itself could be cracked from age or hardened enough that it doesn't engage with the barbs under the swedge collar and can leak there as well.
The hose assembly is cheap, just replace the whole thing.
Flexible plastic is another thing all together. The top has a ball surface that seals when the nut pushes it into the faucet fitting and the lower end has a nut and a compression collar. If the compression collar gets damaged, it can be replaced.
I prefer to use the braided hoses over PVC (Never had a rupture). Their problem area is usually the connection to the shut off valve. I have had new hoses to leak due to over tightening or use of Teflon tape (unnecessary). The remedy is to replace questionable and old hoses. Next, remove unnecessary tape. Then, hand tighten with approximately 1/4 turn (or only enough to stop any leaking).