I have a Delta single handle water control on my shower. It’s 11 years old.

“Full right” position (3 o’clock) is off. “Full left” position (about 10 o’clock) is hot.

I normally set it on about 12 o’clock – straight up. The water is “nice and hot”. Perfect.

I’ve noticed (over the past few months) that the water seems to get slightly cooler after about 3-6 minutes. Not cool, just not as hot. So I have to bump the lever slightly towards the left to get it “hot” again. Probably just a few degrees cooler, not much.

My father-in-law says that after a few years the “o rings” and such begin to loose their flexibility and that’s the problem. I do understand there is some kind of magic inside the valve to keep me from getting scalded when the wife flushes the toilet)

Anyone have any experience like this that was fixed by new “o rings” or whatever innards there are?

My next step is to remember to bring a digital thermometer in the shower to see if indeed it gets cooler, by how much, or mayby just my imagination.

(However, the wife mentioned the same problem to me this weekend – and no, I hadn’t said anything to her about it before!!)

Ideas anyone?