I need some advice. When we are using the shower we have to turn the hot water on full blast and the cold on just a tiny bit or the water is cold. Within a couple of minutes of taking a shower the water gets colder and we have to turn the cold almost off.So there is barely any cold on and the hot is on all the way. We installed new control valves about 6 months ago and the problem has gotten worse over time. Did it get installed incorrectly? We also installed a new water heater within the last month but I don't know if that has anything to do with the problem. The other faucets in the house work correctly.
Thanks in advance for your help!
Mell

Who installed the water heater?

My husband.

Did he apply any heat close to the cold water input? In other words did he screw the adapter into the cold water input and then solder pipe to it?

No I reused the original piping and used shark bite hoses to connect pipe to water heater cut off with pipe cutter so no heat was used. There is no cold water pipe by heater, pipes are in crawl space cold supply in and one hot feed line out to house. House is built in 1952 far as I know the plumbing behind wall is still original for shower head I've had to replace washers in valves before because of drips, this time 6 months ago had replace entire valve guts couldn't find washers so used new valves in older brass housings.

Is tub and shower valve single handle or two knobs?

The shower is two knobs.

Sounds like you have sediment in the shower valve. Remove hot water stem. Briefly turn on the hot water and flush out the valve.

We will try flushing out the valve, I will attach pictures of the valves also.

4570445705

Good luck with that...