100 psi foe the pipes and standard meter for your home which is not so extraordinary.
Why don't you get a plumber to estimate the job since you don't know too much about fluids and piping ?

I was mentioning psi by the charts and not at the meter. I know that psi is greater at the meter and I am merely asking for helpful input on sizing and thoughts of materials. I don't know the exact psi at the meter but understand that it is much higher than 50. Keeping it under 100 is most likely best for piping indoor. Comments about not knowing stuff and consult a plumber is not worth posting on here. I have worked with plumbing but not dealing with 300' run outdoors.

I really just want to know if 1.5" pipe will work or if 2" would be a better route with the WSFU of ~88 assuming a 1.5" meter. I am an engineer and know about fluid and Bernoulli's principle just not on the exact sizing of the main.

This post was edited by stitz_crew on Tue, Jan 29, 13 at 11:21

The black poly is the better choice. Intuitively, I believe that the 1.5" will be sufficient. I would be surprised if they install a meter larger than 1".

Obviously Joeplumb is not a plumber...

stitz crew,

I commend you for your efforts in working out the WSFU formula. As you have learned, that system works very well for quickly computing a 2 or 3br single family dwelling in an urban area where the supply line is 150' or less but when confronted with a large load such as yours and a long service line it leaves a lot of questions unanswered.

Given that you are an engineer I am sure you can appreciate if we take the time to actually engineer your line.

First of all, let us list the code specs and the given information we have at hand.

Code requires that when we design a water service line for a single family residential structure we must design for 100% duty cycle, meaning that the line must be able to supply the full gallon per minute supply & pressure to structure even when all fixtures in the structure are on at the same time.

Allowable pressure at the structure water service "Main Water Shutoff Valve" is a minimum of 45psi and a max of 85psi. If the supply pressure is below minimum we have to install a boost pump and if above 85psi, even intermitently we must install a PRV (pressure reducing valve).

The first step is to make a list of all the fixtures in the structure and use the code table to determine the GPM we are required to provide for each fixture.

I did not have a list of fixtures for your house so I made a best guess based on the information at hand.

You have 5.5 baths so for illustration I assumed one Master Bath(2lavs and both tub & shower), 4 standard bath groups & the 1/2bath

So for the bathrooms we have i estamated;
7 lavs @ .5gpm = 3.5gpm
1 shower @ 3gpm
4tubs @ 4gpm=16gpm
5WC @ 3gpm= 15gpm

Kitchen sink 2.5gpm
Dishwasher 2.75gpm

Wash machine 4gpm
laundry utility sink 4gpm

2 hose bibbs @5gpm - 10gpm

That adds up to a total combined load of 60.75gpm

Now contrary to popular opinion, reducing the size of a line does not decrease the volume of flow, however as the line size is decreased the velocity of flow increases and the pressuree decreases exponentially from "Friction Head Loss"(pressure loss resulting from friction with the pipe wall). By example- if your 60gpm was flowing through a 6" pipe the velocity of flow and pressure loss would be 0.66ft/sec & 0.01si/100' but if you were to attach an 1-1/4" line the velocity in the 1-1/4" would be 10.71ft/sec and the pressure loss would be 11.18psi/100'

Not only does the higher velocity result in pressure loss, it also increases the rate of pipe failure from pipe wall erosion. In an effort to minimize pipe wall erosion the codes limit the allowable velocity of flow to 8ft/sec in copper pipe & 12ft/sec in plastic pipe.

Now let us begin putting it all together.(for your own enlightenment you may want to download a "Friction Head Loss Chart".

They are placing your meter in a vault near the street. If we consult an friction head loss table an 1-1/4" line can handle 60gpm without exceeding the maximum flow rate and it is a short run from the municipal main to the meter (probably in the order of 10'). The friction head loss in 1-1/4" pipe would be 11.18psi/100' or 11.18psi/100 divided by 100 = 0.1118psi/ft x 10ft = a pressure loss from the main to the meter of 0.011psi. Obviously that is neglible, but we now have a run of 300' from the meter to the structure. If we were to then run the 1-1/4 to the house the friction head loss would be 11.18psi/100ft x 300' = 33.54psi. Now assuming the municipal main pressure to be approcimately 60psi the resultant pressure at the house would be 60psi - 33.54psi = 26.46psi, well below the code minimum of 45psi. Even 1-1/2" pipe would have a friction loss of 32psi and you are again under the code minimum at the house. Increasing the pipe size to 2" would yeild a friction loss of 9.66psi. Now when compared to the cost of labor to install the pipe, the pipe is actually cheap. In fact, if it were my house I would run a 2.5" pipe with a friction head loss of only 4psi.

Now that we have discussed friction head loss, we have to also consider VSHL(vertical static head loss) or VSHG(vertical static head gain).

To compute VSH we need to know the actual depth below grade of the municipal service water line.(Usually you can call the water suppliers engineering office, give them your street address and they can tell you)

Now you have to figure out the elevation where your water line will enter your structure. If your house sits back on a hill, even though the line is two feet below grade on each end there could be a subtantial change in elevation between your house and the water main. If your house is uphill the water has to be pushed up to the house and it looses 0.434psi per vertical foot of differential, on the other hand, if your house is downhill you gain 0.434psi per foot of vertical differential.

Now here is a couple tips;
Check with your plumbing inspector. In most jurisdictions they will allow you to install PE or PEX line with a trencher. In fact, some trenchers have a roll pipe rack right on the machine so the pipe is laid while they are digging the trench.

Although it is not required for water service, when I lay a long line such as your I like to run one strand of AWG 16 THHN wire in the trench on top of the pipe. You just leave the ends loose inside the house and in the meter box. In future if you should ever have need to locate the line a signal injector can be attached to the line and a signal tracer can be used to pinpoint the exact location of the line for the full length without any digging.

Also, when they are backfilling about a foot below grade run a yellow plastic marker tape that says "Water" then finish the backfill. In future if anyone shoud happen to be digging in the area they will hit the plastic tape and warn them that they are over your water line. (you can get the marker tape at any big box home supply or plumbing supply house.

Thank you for the responses. Very good information lazypup. I appreciate people taking their time to post helpful information. We are still in the stages of planning the build so I am trying to educate myself the best I can on decisions we will need to make. I want to know the best practices so for plumbing and other aspects of the house when dealing with subs. Instead of reading novels I like to read books on plumbing and wiring which sounds pretty nerdy but useful. So needless to say ive searched my topic and read through many posts and data on plumbing.

I know there are several missing variables to know the exact design but you have brought up several good points. Velocity of the water is what I want to make sure is proper to increase the longevity of piping and avoid wall hammer. In our current home wall hammer is very noticable since utility increased psi at the meter. Will be installing prv to hopefully reduce this and the velocity in the lines.

I will have to check with the utility company about the size of meter they can install and if they charge a higher usage fee based on that. I was probably looking at using a 2" line to be safe considering we may have other buildings down the road. I do like the idea of using a tracer line and caution tape for digging purposes. That would be very useful for underground power as well.