Just had a new water heater installed and now the shower faucet is very sensitive. If I turn it just a bit to the cold or hot side the change in temperature is drastic. Any ideas?

Have you checked what temp the water heater is set at,

I should have added that the faucet is an Moen and is single handle controlled.. Pull to turn water on rotate to adjust temperature.

Is your water heater elctric or gas? Thanks.

John

Gas

It is a tank or tankless

Tank.. Whirlpool 50 gallon

All right check the water heater gas valve for proper setting as other expert mentioned, see the image below, good luck.

John