Dear Kay: First: check to see if the plumber opened up the cold water inlet valve all the way. Water squeals when it is forced through narrow openings. Check to see if the pressure relief valve is seting properly; flip it (lift the lever for a couple of seconds, then let it go quickly) to see if that does anything. Depending on how old your plumbing is, you may have scale buildup in the hot water pipes. Do you have the same flow at all outlets? It definitely sounds like a restriction in the hot side. If you have a lime scale problem, I can help. E-mail me. Good Luck Brian the Waterguyser.