Water pressure in kitchen and front shower is weak,and it takes a little bit before the water starts getting warm.I put a new faucet in a couple of weeks ago the type where it has all the pluming in t

Is the hot water pressure good at other fixtures in the house? I'm guessing your newer valves have a scolding adjustment that is set very low. Check the instructions that came with the valve assembly.

This is going to be a water heater issue. Not the head.

My first suggestion is to have the installation plumber return to adjust the faucet to function properly

You can cap the lines at the tub faucet to rule out tub faucet. It maybe mixing there.

Faucet may be bad also the safety stop will alow you to change water temp it can be tricky to adjust water temp.

Have you thought about possible calcium buildup in your hot water tank/pipes? I am helping a friend in Palm Springs CA (California not Canada) and we are going to pour a really huge pile of vinegar into the hot water tank (let it sit for a day) then open up the hot water taps to the kitchen (where we don't have hot water flowing very well), then going to let everything sit for another day. Remove the aerator from the kitchen faucet after letting the vinegar/water solution sit in the pipes for a day, and turn on the kitchen hot water tap. Once all the **** is drained out, you must of course drain out the vinegar/water solution from your hot water tank or you will smell like French Fries (in Canada we put vinegar on French Fries) when you shower for a few days.

If you don't understand what the basic chemistry of dissolving calcium via this method is all about, then please call a professional plumber. Hope this helps, and remember that Google is your friend (sometimes), but be careful...

The posi temp valve has a little system built inside to anti scald you when your taking a shower, they have little parts that move back and forth, they get easily clogged from sediment and minerals in the water and always get stirred up when the water is turned off and back on from doing work.

That is a graduated water mixer valve, and it sometimes has a little white water restrictor blocking flow from your hot water port. See if that was left in by removing the handle with all water shut off to the valve and reattach then try again. This can also happen if you have a tankless water heater because pressure controls heat. Typically a Tankless water heater system will require little, to no cold water to your bathtub valve because of the heavy water flow at the tap. Remember, flow equals temperature. Less flow = more heat, more flow = less heat.

Try draining the system and apply air pressure (min 30psi) to each faucet. Open other hot water faucets to allow pressure to vent. Next try draining and cleaning the hot water tank.

Those new faucets generally have a lower water pressure due to legislation passed in 2007 that reduced that maximum allowable gpm (gallons per minute). I hate to tell anyone this but there is little if anything you can do. First of all, make sure the shut-off valves are open completely. I know that sounds elementary but I've seen it a bunch of times.

Also check to see if the aerator is blocked with a bit of debris.....unlikely if the flow is uniform but still an easy fix.

Hope I didn't break your spirit too much....

I found a way to get warm water in the shower, but I'm not sure it qualifies as a solution. After trying everything else I thought that maybe when I was feathering the faucet in the shower toward the cold side so I would get warm water that at a certain point it blocked the flow on the hot water side enough so that the sensor in the hot water heater sensed there was no demand in the line and it shut the water heater off. To test this, I went to the kitchen and turned the kitchen sink faucet all the way to the hot side and then turned it on so that I got a small flow of water. I waited for the water to get hot to be sure the hot water heater was working. Once it was hot, I left it running to keep demand in the line and then I went to the shower and turned the faucet on. When the water got hot I started feathering the control towards the cold side and soon I had warm water. So I think I'm right in that the sensor in the hot water heater was shutting the water heater off when the demand in the shower was lowered to a certain point when I was trying to adjust the water temp in the shower.

So now I can get warm water, but it means I have to leave the hot water running at another fixture in the house to create a false demand in the system so the hot water heater doesn't shut down. Is there a way to adjust the senor in the hot water heater so that it will stay on when I'm using the shower only, so I don't have to waste water by running another faucet when I want to take a shower?