Pipe Reduction At House Entrance

[TouchOfGrey]

Currently I have a 1" meter at 55psi that connects to 1 1/4" pipe running to the house, about a 40 foot run. At the house entrance it reduces back to 1" for 2 feet before going back to 1 1/4" inside the house. The total developed length is then about 150 feet. Looking at the WSFU charts, if I didn't have that small reduction of 1" pipe, I would be able to supply 52 WSFU. However, if the whole thing was 1" pipe I would be able to supply 30 WSFU. So my question is, how much do I lose with that 2 foot section of 1" pipe? Would I still end up closer to 52 WSFU because the friction loss is so small for that length? Or does it create a different limiting factor that pushes me toward 30 WSFU?

 

[wwhitney]

Interpolation is reasonable here. So for 2' out of 150', you'd lose 1/75 of the benefit of the larger size, i.e. maybe 1 WSFU.

Another way to look at it is that the empirical Hazen Williams equation says the pressure drop is proportional to the pipe diameter to the -4.87 power. So if the actual ID is the nominal diameter (not true, use the actual IDs for the type of pipe you are using to get a better answer), 1 foot of 1" pipe is equivalent to (1.25/1)^4.87 = 3' of 1 1/4".

So with 2' of 1" pipe, and maybe throw in another 2' for the equivalent length of the transition fittings (total guess), that's 12' equivalent of 1-1/4" pipe. I.e. just add 10' to your equivalent lengths to make up for the 2' section of 1" pipe.

Cheers, Wayne

 

[Sponsor]

 

[Jeff H Young]

I wont tell if you dont tell. I think youll be ok you probebly have several feet of 1 inch going to the curb stop as well . In a perfect world tear it out drill bigger hole in foundation or whatever the problem is that someone ran 2 ft of 1 inch .

 

[Reach4]

The flow a system can do is not just a function of the smallest piece. The resistance adds like series resistors in electronics.

It is fairly common to use a 5/8 or 3/4 inch water meter, and then continue to the house with larger pipe.

 

[Fitter30]

Big drop is through the meter. 52 wsfu = 52 gpm . 1 gpm per 1 wsfu
1.250 pipe can't support 52 gpm
2" nps has 5 gpm drop 5 ft per second.200' equivalent lenght
2.5" nps has 1.8/gpm drop 3.5 ft per second 200' equivalent lenght

Calculator: Pressure Loss through Piping for Water | TLV - A Steam Specialist Company (North America)

Online calculator to quickly determine Pressure Loss through Piping for Water. Includes 53 different calculations. Equations displayed for easy reference.

www.tlv.com

 

[TouchOfGrey]

Thanks for the help. You’ve confirmed that I wasn’t missing anything essential. And Jeff, you nailed the exact situation - wrong hole size in the foundation