water mixing temperature

Hi all, After the plumber replaced my hot water pipe to the water heater, 2 of my showers and 1 kitchen faucets lost pressure on hot water( I guess that’s the right term) they were all working fine before that. All 2 shower valves and faucet are mixing valve, which is sharing 1 valve in the same...

This isn't for a project, but rather an inquiry for my general knowledge as I can't seem to find my answer anywhere online. I am a novice in DIY plumbing(e.g. installed a few sink and tub faucets) so bear with me as I will do my best to explain. I recently moved into a new apartment in Dallas...