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guyod 03-28-2008 12:41 PM

using 3/8 hot water line
Hello everyone

The hot water heater in my ranch is about 30+ feet from the kitchen and it takes forever for the hot water to reach the sink. I was thinking about running a 3/8 water line to speed things up. it would be cpvc. and there will be a dishwasher. will 3/8 be enough water for the sink and dishwasher? will it even make a difference in heat time? Let me hear your thoughts thanks.

glennjanie 03-28-2008 07:25 PM

Hello Guyod:
I would run a 1/2" hot water line which can support up to 3 standard fixtures. The 3/8" line would starve the fixtures for lack of water. In Kentucky, we don't run a 3/8" line over 30 inches. Best wishes with your project.

travelover 03-29-2008 09:07 AM

How about using one of those small circulating pumps that they sell at Costco etc? It circulates the hot back into the cold line so no water is wasted, and is switched so it only runs when you need it. Another option is to run another hot water line back to the bottom of the hot water heater and let natural convection circulate the water. I have this at my house and it works great - just wastes a small amount of heat.

guyod 03-31-2008 07:41 PM

How does the hot water line connect to the bottom of the tank? I have only seen mobile home hotwater heaters with the bottom inlet.

Square Eye 03-31-2008 07:52 PM

Cold side connects on top but the pipe runs to the bottom of a water heater on the inside. :)

guyod 03-31-2008 08:11 PM

Do you need a check valve to stop the cold water from mixing with the hot water ?

Square Eye 03-31-2008 08:42 PM

The theory is, you run a loop out of the water heater, out to the fixtures, "T" right past the fixtures and bring it back to a "T" in the cold line inlet at the water heater. The water will be considerably cooler after traveling the entire circuit and the water pressure will still be on the street side so hot water backflow shouldn't be a problem. Keep in mind this will use more energy because the water heater will be circulating cooler water in at all times instead of just when the hot water is being used. Also, (keep in mind, I'm no plumber lol) I think if you add a check valve in a line where there is a heating device, you will have to add an expansion tank in the loop.

glennjanie is my personal authority on plumbing :)
I'm sure he will correct me if I'm wrong or add if I have left anything out.

travelover 04-01-2008 05:33 AM


Originally Posted by guyod (Post 17480)
How does the hot water line connect to the bottom of the tank? I have only seen mobile home hotwater heaters with the bottom inlet.

On my water heater, the return line Tees with the drain valve. This will use some extra energy. Be sure to insulate the lines.

glennjanie 04-01-2008 12:41 PM

Square Eye is 100% correct. Some municipalities now require a check valve at the meter and some have just put them in without knowledge of the homeowner. It does require an expansion tank though, because the water increases in size by ~2 1/2% when heated. Since water does not compact it leaves the weakesst point to blow out (usually the water heater).
Loops are great though, for instant hot water at the faucet and are easily self-powered by convection. Insulation of the lines is crucial.

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