It seems there's no "plumbing help" thread so here's one and here's my question:
Just about 2 years ago I got a new water heater, everything was all fine and dandy.
About 6 months ago I redid one of my bathrooms, which until then was not really used that often, it was very old and the tub drained very, very slow. After the construction (new tub, new toilet, new sink but not new plumbing) we started using the bathroom daily.
At about the same time the bathroom was complete and now being used normally, the water heater relief valve started leaking (for lack of a better word, since it's not really a leak as it's designed to relieve the pressure if it gets to high) so I called up rheem and they sent me a replacement valve, I had it replaced and it still leaked :-( I called rheem again and this time they said I would need to install an expansion tank which is not covered under warranty. Not wanting to shell out the $400 my plumber wanted for that I just settled with the fact that I will empty the bucket I put there daily and live with it until I win the lottery.
Now here comes the fun part, we were away for the first days on succos through monday night, so were out of the house from wednesday afternoon through monday and obviously with nothing being used the bucket was empty when we returned but each day I checked I noticed it was still empty until this past sunday which is the first time we used the shower in the new bathroom since we returned (we were using the toilet immediately when we returned but not the shower). Based on this and the fact that it only initially started to leak after we redid the bathroom I blame the new shower entirely.
So what would be causing it and more importantly how can I fix it? What I find the most strange is if I did need an expansion tank why wouldn't it leak always regardless of what is being used? (we were using the other shower and had no problems, only when we used the new shower did it start to leak again)