2 water line questions

can we use flexible plastic pipes for water lines (hot and cold) inside a house (kitchen)?
and the second question concerns water flow.
the way the water pipes are right now in my house, one main (3/4 inch or so thick) water line comes in the house. this splits in several places to go to the water heater (for running water, the hot water boiler (for heating the house) and cold drinking water.
from the water heater I have one pipe coming out and splitting in the garage. on one side it goes in a water column for the bathrooms (on 2 levels) and on the other side it splits in a column for the kitchens. all these pipes are usually 1/2 inch thick. the only one that's larger is the main entrace one.
now, for some reasons, I want to change the lines that go to the upstairs kitchen. since all pipes eventually come in the same (1/2 inch) pipe at the water heater, does it make a difference if I split the bathroom pipes upstairs and take a new branch to the kitchen, or run a new pipe all the way down to the basement to add another split close to the water heater? I'm thinking in terms of water debit, if someone uses the bathroom and kitchen at the same time.
this would mean that two bathrooms and one kitchen areo n the same water pipe, but eventually all pipes come in the same place anyway, so woul the debit drop or stay the same regardless of where the pipes are split?
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j j wrote:

I'd use the braided stainless steel line in the kitchen. If you decide to use an instant hot water heater, never use plastic flex pipe. Use copper pipe for the hot water feed to dishwasher with brass compression fittings. NOT PLASTIC!

Only problem with this is if the dishwasher is being used you will get a hot/cold fluctuation's at the shower fixture. Which can be pretty dramatic
Rich
--
"You can lead them to LINUX
but you can't make them THINK"
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If you feed multiple half-inch lines from a single half-inch line coming out of the water heater, two comparable draws (like the washingmachine and the shower) are going to share what flow is available. You should be able to create dramatic temperature variations in the shower in a variety of ways, and certainly when I lived in a dorm in college this was considered a form of entertainment, so it may not be a bad thing. Depends on how well you get along with the rest of the family. There should really be a 3/4 line from the heater with the half-inch lines branching off it.

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