hot water won't drain.

I have a customer that has a problem with drainage of sink. He has installed a new sink, it drains fine with cold water but drains slow or not at all with hot. If he adds cold it will drain. I haven’t seen this before. Any ideas?

Did you actually see this yourself?
My best guess would be that there is some type of greasy/hair build-up in the piping, most likely in the P-trap so when hot water is used causing grease/hair becomes loose, creating blockage, and when the cold water is applied it causes the greasy/hair substance to cling and harden allowing the cold to flow again. I say pull the trap off and inspect it.

As inspector we should not pull anything apart to inspected, you will recommend a qualify plumber to look at the sink, inspector only do visual inspection and are not require to pull thing off.

From what I understand from this original question is he was referring to previous customer that has this problem, not something he viewed during an inspection.

I told him to check the trap for a clog, if free call a plumber, it is out side the scope of a home inspection. To clear up my question, I did not pull anything apart nor would I. The question was… has anyone seen this condition before and any ideas on what might be causing this?

I have a couple of ideas.
A: He’s messing with you.
B: He’s completely crazy.

I’ve been an inspector for over ten years, and I’ve been doing commercial building maintenance for 15. I’ve seen the best most creative ways humanly possible to stop up a drain, and I’ve never seen one do anything like that.
I’ve seen them do the opposite, hot water good - cold water bad, but never what you described.

If I were you, I’d have to go look at it myself, just to see.
Either way, you’re not on the hook from a liability perspective because it’s not the same sink that you inspected, right?
Helping the guy out is fine, but don’t let him turn it around on you.

That’s how I read it too. I was just giving you my thoughts of what it might be. To clarify things, when I said “I say pull the trap off and inspect it”, was not directed at you to do it was only a suggestion to help find the possible cause.

I agree Andrew, this is quite unusual

I’ve been inspecting for over 16 years, real estate sales for over 14 and building trades before that, You could say my entire working life… never seen this either, this one is not on me, different sink installed by plumber.