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Author:
EPB (IL)
My house has 3/4" copper pipe coming in off the Well mate. The house currently has 1.5 baths (both have single sinks), a laundry area and a kithchen sink. The full bath has a combined tub and shower. The half bath has a spot for a shower stall that is currently unused.
I am adding an upstairs addition that will have a laundry area, a full bath with a tub, seperate shower stall and a double sink. This upstairs addition will also have a kithenette sink.
Will 3/4" copper pipe have enough flow considering the additional fixtures? How do you determine what is an adequate flow rate and proper pipe size? How much flow in 3/4" cu pipe vs. 1" cu pipe?
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Author:
hj (AZ)
The question is, "how many of the faucets in the house will be turned on at the same time?" Next, if they are standard faucets, the opening for the water to acutally flow through is about an 1/5 the size of a 3/4" pipe. Many, if not most, homes with your demand are piped with 3/4" copper.
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Author:
jmenacker (WV)
The link above shows flow rates at a velocity of 1 foot per second. The chart shows a best flow rate in a 2" schedule 40 (cpvc, steel?) of 0.174 gallons per minute. I suspect that most domestic water systems do not have 3" or 4" supply lines feeding a drinking fountain. Therefore, basing a water supply system on a maximum flow rate of 1 foot per second appears too conservative.
Here is a link with tables for flow rates of 3 feet per second and 3.5 feet per second. To tell you the truth, I have been designing hi rise residential plumbing systems for 20 years and normally base design on a maximum of six feet per second.
[www.plumbingsupply.com]
Condideration must also be given to the fact that resistance to flow increases with velocity. If there is not an abundance of pressure available, then larger piping is required to conserve pressure for remote outlets.
At three feet per second even a 1/2" pipe has a pressure drop of only 4 psi per 100 feet of pipe (new type L copper). There doesn't seem to be much sense in designing for less than 3 feet per second unless some extremely rough walled piping is involved.
Joe M in WV
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Author:
royboy (SC)
Good post jmenacker. All plumbers should at least occasionally look at the charts in the back of the code book refering to the flow rates through various size and smoothness of the pipes we use. As pex and other piping materials are being utilized we can give the customer a better plumbing system. Believe it or not, many people will pay extra money if they are educated in this area.
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Author:
EPB (IL)
I checked the GPM at the kithen faucet and the bathtub. Both are 1/2" copper fed off of the 3/4" line. The tub is approximately 15 to 20 ft of pipe from the wellmate. the kitchen sink is approximately 20 to 25 feet of pipe from the wellmate.
Kitchen - time to fill (1) Gallon = 40 Seconds
Tub - time to fill (1) gallon = 12 seconds
So I am guessing the system is around 5 GPM. We have seven persons in the family and that may mean two showers and and possibly a bathroom faucet being used at the same time.
I am a little foggy on what this all means. I know a little about the subject but not enough to figure out what to do here.
Edited 1 times.
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Author:
hj (AZ)
All you know is how much water those two faucets can deliver. It has nothing to do with the capacity of the system.
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Author:
steve_g (CA)
I get 1" minimum, 1ΒΌ" if it's a longer run (up to 60'). 32 FU on the low pressure scale (well). Is there another way to figure it?
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Author:
EPB (IL)
I checked the pressure gage cut-in and cut-out. The pressure is 60 psi (cut-out) and 40 psi cut-in.
When turning the tub water on and checking the pressure gage, it takes 60 seconds to go from 60 psi to 40 psi. Once the pump cuts-iin at 40 psi, it takes 70 seconds to get back to 60 psi (with the tub water still running). I have a 22 gal well tank. I am not sure of what horsepower the pump is.
So, I am guessing I have more then 5 GPM but how do you figure this with the info I have?
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