Long Water Service 1

[Builder604]

My wife and I are getting ready to build a house on a large parcel and our house (1 story 5 bedrooms 5.5 baths) will be approximately 2400 feet from the meter. The house location is at most 10' higher than the meter. The county has already installed a 1" tap and meter for the parcel. The static pressures of the closest hydrants are 92psi and 90psi. According to some preliminary calculations a 1.5" pipe from the meter to the house would result in a head loss of 41psi at 20gpm. That would leave about 50 psi at the house. If I went up to a 2" pipe the head loss would be 10.2psi at 20gpm but I have concerns about stagnant water in the 2" pipe.
I would appreciate some input/advice from anyone who has dealt with a long water service. Thanks.

 

[1503-44]

No stagnant water there.

Reality used to affect the way we thought. Now we somehow believe that what we think affects reality.

 

[Compositepro]

41 psi at 20 gpm is good for a house. You probably need a pressure regulator at the house so the pressure does not go up to 90 psi at low flow.

 

[curtis2004]

Hi Builder604,

1 1/2" should work fine for your house with 5 bathrooms.
If you use HDPE rolled pipe, it probably not much difference for the cost difference between 1 1/2" and 2". If in future you decide to split your land and build a second (third or even more houses), it could be better to install 2".
Regarding "stagnant" water, you will have it weather you use 1.5" or 2". In order to protect your line you have to dig your trench below frost line at your location. Where geographically are you located?

Thanks,
Curtis

 

[EdStainless]

Why would your demand ever be above 6gpm? The only thing that I have that draws 3gpm is an outdoor hosebib.
Even if you use 10gpm you are down to about 10psi drop in 1.5 pipe.
Are you going to run poly? It is smoother and it will stay smoother.

Low velocity in 2" could be an issue. That is a bit over 400gal in the line, will you turn this over often enough to assure that you have chlorinated water in your plumbing?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Builder604]

Thanks for the input. I just used the 20gpm for rough calculation purposes. I had some concern about the low velocity as well in the 2" pipe. Our frost line is 18" I believe, here NC but will definitely confirm before installing. I just had a local plumbing supply place quote me pipe and the 20' bell end pipe is $0.65/ft and 500' roll of black plastic pipe is $1.57/ft, which is quite a bit of cost difference. I like the idea of having only 5 joints for the roll vs 120 joints for the stick pipe. But I think the budget is going towards the bell end pipe.

 

[itsmoked]

Out of the box:
How about a little 200 gallon tank.
A modern VFD based pressure pump.
Run 1/2" pipe.

The tank will buffer.
The half inch can supply whatever it's rated flow to keep the speed down via a simple float into the tank. The tank gives you the ability to flow big if you need it. Three showers and dishwasher and the lawn.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Compositepro]

PVC pipe will crack if it freezes, polyethylene is much more freeze resistant. I'm surprised at the cost difference.

 

[cvg]

the buffer tank is definitely the way to go

 

[fel3]

You may want to revisit your peak demand guestimate. A house with 5 bedrooms and 5.5 bathrooms is much larger than most of us have. If you have a large family and/or will have guests, you could end up running a lot of water-using devices at once and this might result in a household peak demand that exceeds 20 gpm. If you will have irrigated landscaping, and irrigation could happen at the same time as normal household water usage, you should add the peak flow for the largest irrigated zone. If you will have a swimming pool, you might also need to add an additional demand for filling and refilling (I have an automatic filler on my pool and it probably maxes out at about 2 to 3 gpm).

I did a quick Water Service Fixture Unit Method calculation (based on very little data) and came up with an estimated 53.5 WSFUs and a peak household demand of about 30 gpm. Please see the attached spreadsheet.* The Fixture Unit Method is designed to be conservative, so actual peak household demand should be less. However, I prefer to design using the accepted and code-compliant method unless I have good reasons for doing otherwise. All that being said, most of my experience using the Fixture Unit Method has been for large commercial and industrial developments and state and federal prisons. I have only applied this method to residential cases a handful of time. If you have a plumbing engineer, I suggest you have him/her calculate the design peak demand for your particular project.

For this calculation, I assumed the following:
[ul]
[li]Three bathrooms with bathtubs or bath/shower combos, two bathrooms with showers, and one with neither.[/li]
[li]One clothes washer[/li]
[li]One dishwasher[/li]
[li]A maximum of two hose bibbs on at a time (for a house this large, I figure you will have more than the usual four I see around here, but you probably won't have more than one or two on at a time)[/li]
[li]Eight lavatory sinks in the bathrooms (two in the master, two in another, and four in the remaining 3.5)[/li]
[li]One bar sink, one kitchen sink, one sink in the laundry room, and one service sink in the garage or workshop[/li]
[li]Six 1.6 gallon per flush water closets[/li]
[/ul]

* BTW, all of you are welcome to use this spreadsheet as you see fit. I already deleted my company's logo, but you will need to delete my name and initials from headers, footers, and a couple places within the spreadsheet tabs. I first made this spreadsheet while working for myself, so I didn't steel it from my current employer and it's mine to give away. Also, if you find any errors, please let me know.


============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[1503-44]

"Run 1/2" pipe"
Probably not allowed. You might want to check with your local building code/official about design flow rate calculations and minimum pipe diameters. And I also suppose you have no emergency fire fighting needs at your property. 2400 ft run sounds like it is out in the country and perhaps subject to at least a grass fire. How long until fire department arrives? Make that 2400 ft run with larger diameter and end with a tap. Install tank and vfd at the house, if you want that, but as we have learned from California, vfd power might be unavailable during wild fire emergencies and their aftermath.

Texas IRC

AP201.1 Size of Water-Service Mains, Branch Mains and Risers

The minimum size water service pipe shall be 3/4 inch (19.1 mm). The size of water service mains, branch mains and risers shall be determined according to water supply demand [gpm (L/m)], available water pressure [psi (kPa)] and friction loss caused by the water meter and developed length of pipe [feet (m)], including the equivalent length of fittings. The size of each water distribution system shall be determined according to the procedure outlined in this section or by other design methods conforming to acceptable engineering practice and approved by the building official:

https://up.codes/viewer/texas/irc-2015/chapter/P/sizing-of-water-piping-system#P

You need to do your material selection using INSTALLED COSTS. Ask your plumber for cost to install each material option. The long pipe roll may cost more, but that is usually offset by much cheaper installation costs.

Reality used to affect the way we thought. Now we somehow believe that what we think affects reality.

 

[Builder604]

fel3 thanks for your input and the spreadsheet. It will be very useful!