I am putting a tankless gas water heater in my home. All of the copper
is in the concrete slab so I am going to run an insulated copper tube
"up and over" to the kitchen. The water heater will be a foot from the
two bathrooms and showers. the "up and over" tube will feed the kitchen
sink and dish water - nothing else.

How much water is in a 100 foot by 1/2 inch copper tube?
How much water is in a 100 foot by 3/4 inch copper tube?
How much water is in a 100 foot by 1/4 inch copper tube?

I am too lazy to look it up - I am wondering if any of you experts on
here have the info off-hand. I am thinking of putting thinning tubing to
the kitchen because less water would be in it to cool down etc.

Right now I am running two 50 gallon electric water heaters in a house
for two adults - I am wasting alot of energy keeping all that water hot
- and the tanks are far away from where the hot water is needed anyway
running thru a cold concrete slab.

Harry