3/4" CPVC for main run


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Old 09-01-06, 06:31 AM
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3/4" CPVC for main run

Is it okay to use 3/4" CPVC for the main hot water lines in house? I would then branch off with 1/2" CPVC for each fixture. I've heard this can help with water flow control.
 
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Old 09-01-06, 04:18 PM
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You are right on target. Run the 3/4" as far as you can and branch off at the last minute to the fixtures. Use it for cold water lines, also. This will provide good water pressure not only at the fixture you are using, but at an ajacent fixture. I have that in our house and can hardly notice when someone flushes a toilet.
 
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Old 09-03-06, 09:59 PM
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Thanks for the reply. After asking this question I had a thought:

Wouldn't this waste at least twice as much water as a 1/2" line? If the 3/4" line holds roughly twice as much water as a 1/2" line, then it seems like it would take twice as much time and water to run enough hot water to actually get hot water to the fixture.

Or am I over-thinking this too much?
 
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Old 09-03-06, 11:20 PM
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Well, you're right, it WILL take longer to get hot water to the faucet. Everything in life is a compromise. Which do you want, qyuick hot water or the ability to run more than one tap at a time?

This is why the latest trend is to run individual lines (PEX tubing) from each faucet back to a manifold located at the water heater outlet.

Another option is to install a recirculation pump that will periodically pump the cooled (hot) water back to the heater. There are several different ways that this is done. The easiest is a gravity-flow recirculation system but it requires the water heater to be located below the lowest supply piping.
 
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Old 10-11-06, 10:17 AM
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An update to my original post:

The main water line entrance to the house, and water heater are in the middle of the house. On one end of the house is where the bathrooms are, so on that one, I ran 3/4" for both the hot and cold, and then branched off with 1/2" for the fixtures.

On the other end of the house there is only the kitchen sink, and a outside hydrant (exits the house right below the floor where the kitchen sink is.). I'd like to run 3/4" cold so I have a larger line running to the outside hydrant, but it seems pointless to run 3/4" hot all the way over there (it's about a 25 to 30' run from the water heater to the kitchen sink/hydrant) when all of the other fixtures using hot water are on the other side of the water heater.
It seems to me that if I've already got 3/4" hot running from the water heater to the bathroom fixtures, that turning on the kitchen sink on the opposite side of the house won't effect the pressure on the bathrooms, whether it's on 1/2" or 3/4", so why not use 1/2" so I don't waste as much hot water?
Will this cause a disparity in the water pressure at the kitchen sink if I run 3/4" cold and 1/2" hot for the 25 to 30' from the water heater to the kitchen? (I would still branch off the 3/4" cold line with 1/2" to the fixture.)
(I hope this makes sense!)
 
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Old 10-12-06, 04:49 AM
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The reason you run the 3/4" as a main run is not to move hot water faster or anything like that. You will find the pressure drop is alot less at a given appliance (shower) when someone uses another appliance (toilet). You get the idea? I have mine run like that and can barely discern when someone flushes while I am in the shower. Besides having a scald protector, the pressure does not drop. When you neck down the 3/4" at the appliance to 1/2" you will have enough water to operate it and still allow enough at the other end of the house. Don't worry about "losing" hot water in a 3/4" pipe. You should install the foam pipe wrap anyway, so it will tend to keep things temperate for a longer time.
 
 

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