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Size of line for main service at 1400 ft

Posted by ramsey6557 (My Page) on
Tue, Jan 31, 12 at 10:50

Any one tell me for sure what size watter line to use from my meater to the house to prevent problems from presure or shower scald when toilet is flushed.?? Facts>> Elivation from meater to house is only 10 ft or less.. House is 2 story with 2 1/2 bath with built in dish washer ( 1 bath is upstairs rest of watter is down.) NO IRIGATION system. Location is SE Tennessee aprox 25 mile north of Chattanooga. I dont want to overkill it because I cant afford to wast money but I dont want problems later ether. Thank you


Follow-Up Postings:

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RE: Size of line for main service at 1400 ft

Is that 1400 feet?


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RE: Size of line for main service at 1400 ft

Yes Thats one thousand four hundred feet (1400 feet) from meater to hook up at house.


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RE: Size of line for main service at 1400 ft

What's street pressure?
What type of pipe?
Plenty of pipe friction loss charts available on the Internet

Continuous pipe no fittings, off the top of my head using poly CST it will be 1-1/2" minimum, probably 2"


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RE: Size of line for main service at 1400 ft

dont know pressure yet all watter company will say is allthough pressure is more all they have to guarentee minimum of 20psi at meeter. Pipe is PVC 20 ft sections and strait shot except for 1 turn.


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RE: Size of line for main service at 1400 ft

"Pipe is PVC 20 ft sections"

Every joint creates turbulence to flow and takes away some pressure when the water is moving.

There really are advantages to seamless for applications like this.


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RE: Size of line for main service at 1400 ft

1 foot of head = 0.433 psi
Your gonna lose 5 psi with that 10' elevation already.
If you put 70 joints in that pipe, would be equivalent to adding 210' of 1-1/4" to the existing 1,400.
If you used 1-1/4" PVC pipe and fittings alone with elevation, at 10 GPM you lose 30 PSI.
Looks like 1 continuous roll of 1-1/2" at a minimum would be the course of action.
Better get some professional advice on this and I would avoid the 70 joints that will likely have problems later.


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RE: Size of line for main service at 1400 ft

Per IRC table T903.1 & UPC table 903.1 the load is 32.25gpm

To run the 1400ft line with sched.40 PVC you would need 69 couplings and two male thread adapters(one on each end)

Fitting insertion losses are expressed as an equivalent length of straight pipe.
An 1-1/4 coupling = 1.25' x 69 couplings = 86.25'
An 1-1/4 male thread adapter = 2.75' x 2 MTA's = 5.5'
Total developed length = 1400'+86.25'+5.5'= 1491.25'
1-1/4" pipe @ 30gpm FHL (friction head loss) = 0.1185psi/ft

1-1/4psi @30gpm the friction head loss is 1491.25' x 0.1185psi = 176.31psi loss to pipe friction plus 4.33psi Vertical static head loss so the total loss is 180.64psi.

with 1-1/2" the loss is over 85psi
with 2" pipe the total loss is over 28psi
with 2-1/2" the loss is over 14psi

3" sched 40 couplings equal 3' x 69couplings = 207'
3" male thread adapter = 6.5' x 2 = 13'
TDL = 1400' + 207' + 13" = 1620'

3" sched 40 @ 30gpm FHL = 0.0023/ft x 1620' = 3.76psi loss

Total loss = 3.76psi FHL + 4.33 VSH = 7.52psi

Min Static head at the main water shutoff in the structure is 40psi therefore if the pressure on the municipal main is less than 47.52psi a boost pump would be required even with 3" pipe.


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RE: Size of line for main service at 1400 ft

1-1/4" poly is only .87 psi per 100' @ 11 GPM.
Continuous pipe is only over 12 PSI plus end fittings and VSH
Keeps it under 20
I would think 1-1/2" continuous roll would be the way to go?


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RE: Size of line for main service at 1400 ft

Quote:"1-1/4" poly is only .87 psi per 100' @ 11 GPM."

That is true, but the load is not 11gpm, its 30gpm and @ 30gpm the loss in PE pipe is 5.2psi/100ft. (0.052psi/ft)

1400ft x 0.052psi/ft = 72.8psi loss


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RE: Size of line for main service at 1400 ft

Lazypup,

Why would the load be 30 GPM?
When residences are piped with 3/4 and 1" services and 3/4 distribution systems?
You counting every fixture on? We know there isnt a house in TN that could do that.
A common well pump is 7-12 GPM, my whole street service isntover 6"


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RE: Size of line for main service at 1400 ft

Contrary to the general public opinion, there is absolutely no guesswork in Plumbing. Plumbing is simply a big math puzzle that is defined by code specifications.

When designing a water supply & distribution system we begin by making a list of all fixtures in the structure and consult the code table to determine the demand load for each fixture.

In this example we have 2.5 bathrooms, a dishwasher and no irrigation so refering to table T 2903.6(1) we get the following load:

BATHROOM #1;
Lavatory............ 2
W.C. (tank type)... 3
Tub/shower.......... 4

BATHROOM #2;
Lavatory............ 2
W.C. (tank type)... 3
Tub/shower.......... 4

Kitchen sink........ 2.5
Dishwasher.......... 2.75

Laundry ............ 4

Hose Bibb........... 5
____________________________

TOTAL LOAD......... 32.25gpm

For single family residential applications code requires we design the water supply line at 100% load(rounded off to the nearest 5)

The load was 32.5 so I rounded to the nearest 5 and ended up with 30gpm.

For multi-family (up to 4 living units) & commercial multi-family (five or more living units code allows us to de-rate the load,(typically 80% for multi-family & 60% for commercial multi-family.)

Next we must determine the TDL (total developed length) of the line. TDL = length of the pipe + fitting allowances.

FITTING ALLOWANCE-The additional friction introduced by a fitting expressed as an equivalent length of straight pipe.

When you consult a Friction loss table you will note that is expresses both the friction loss in psi/100ft & the velocity of flow.

To prevent pipe wall erosion Code limits the Velocity of flow in a copper pipe to not more than 8ft/sec and 12ft/sec in plastic pipes. (Generally the friction loss tables only list the numbers that are within the velocity of flow range, or they may list all pipe sizes, but those that are within the velocity flow range are color highlighted.)

Next we need to determine the VSH (Vertical static head) loss. If your municipal water main is 10' below grade but the main water shutoff valve is 1' above grade on a slab house the vertical offset is 11' @ 0.434psi/ft vertical so the VSHL= 11 x 0.434= 4.77psi loss.

Code requires a minimum static head pressure of 40psi at the main water shutoff valve so we add the minimum supply pressure & VSHL, then deduct that from the municipal main static head pressure and use the friction head loss tables to determine the size of line that can supply minimum pressure at the structure.

Typically on a municipal main the physical setback from the main to the structure would be in the order of 50'-100'

For sched 40 PVC pipe @ 30gpm FHL (friction head loss) =
1" pipe..... 46.08psi/100ft
1.25" pipe.. 11.85psi/100ft
1.5" pipe... 5.53psi/100ft

For illustration, let us assume a typical urban house on slab with an 11ft VSH from the main to the water valve and a 50ft setback from the main to the house.

We then add the code minimum pressure (40psi) plus the VSH (4.77psi)and deduct that from the municipal main pressure.
Assuming a main pressure of 60psi we then get 60-44.7= 15.3psi.

We have a differential of 15.3psi and the 1.25" pipe is only 11.85psi loss so if you use 1.25 you still have a margin of 3.45psi.

In fact, if the municipal main pressure was excessively high we could opt to slightly undersize the line thereby using the FHL to reduce the pressure thus negating the need of a pressure reducing valve.

On the other hand, the original problem here is that the supply line is over a 1/4 mile long so we have to increase the diameter of the line to reduce the FHL.


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RE: Size of line for main service at 1400 ft

Of course that rediculous right?
A family of 4 in the bathroom, all four showering, brushing teeth, flushing toilet simultaniously while clothes washer is filling and dishwasher is rinsing all while a ghost is running the kitchen faucet while a neighbor steals water from your outdoor spigot to wash his car while the family of 4 are a multi-tasking in their bathrooms?


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RE: Size of line for main service at 1400 ft

I have worked in 7 states and all but one of those states would require pulling a permit prior to commencing this work.

In every case they require that you submit the complete specifications including the math in order to pull the permit.

I am only illustrating the manner inwhich a real plumber would work out the details in accordance with current code standards.

I personally could care less how the self appointed experts derive their solutions.


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RE: Size of line for main service at 1400 ft

Along those same lines, I've lived in 9 homes, 4 states, and none of them could flow every fixture simultaneously. I guess it's rarely enforced?


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