New water line, starting from 0. What sizing and line should I run ~600ft in TX

[Mattg43]

Hello all! I have been doing some digging and finding different things at different places, and wanted to get a more solid foundation to plan around.

Appologies about the length and probably duplication due to lack of reading on the site (but I have spent quite a bit of time here).

When I say I am starting from zero, I mean there is no water to my property at all. I am working with the local utility district to run a new water line, and that will be a 2" to the corner of my property. This is going to cost a significant amount of money to set up and get ran, so I want to do it right, efficiently, and as affordably as possible without any shortcuts.

The paperwork they gave me shows a "5/8x3/4 meter". I assume I may need to request a 1" meter, but I am not sure. From here back I plan to run about about 600 ft back into the property to a small utility shed with a manifold with shutoffs to go out to a future shop building for a sink and hose bib, and over to the house after a water treatment of some kind.

From the meter point back to the house, there will be a net zero elevation change to the highest fixture. It is slightly down hill and there will be a bonus bath above the garage in the future, though no plans for it to be used regularly.

The house we are planning on building will be 3.5 bath with said bonus room bathroom.

The rough fixture count will be:

1 large soaking tub.
1 bath/shower combo
2 showers, one will have rain shower head plus body sprayer.
5 lav sinks
4 toilets
1 kitchen sink
2 utility sinks
1 clothes washer
3 hose bibs.

There may be a VERY RARE occasion where more than 3 items total will be used at the same time, but generally speaking about the worst case scenario would be 2 showers with the dish washer going, or shower + laundry + outside hose bib, something along those lines. Normal use will be 1-2 items at any given time, based on current use at our house now (a 2.5 bath)

The distance is what has me concerned - I have some local people telling me 1" will be fine for the house, but I think this is not taking into account the distance. The plan was for PEX to be used underground, as I have seen some PVC damage caused by shifting ground around the area with recently built homes, and the lines will be difficult to reach and repair, and it seems PEX is a bit less prone to damage with the flexibility.

Any advice or suggestions to do this right will be greatly appreciated!

Matt

 

[Sylvan]

I would not use any diameter smaller then 2"

 

[Sponsor]

 

[Terry]

And below a chart for PEX

 

[wwhitney]

How an engineer would do this:

1) Determine the peak demand gpm for your property. The plumbing code has a concept of supply fixture units, but I'm not clear on those details and how that translates into gpm. Don't forget irrigation. If you want to have fire sprinklers, that may control the demand.

2) Find out out from the utility the available static pressure, and residual pressure at your demand gpm (or at some higher gpm they choose) that will be available at your meter location.

3) Determine the elevation gains involved. Sounds like in your case it would be conservative to ignore elevation, you don't need to serve any fixtures at significant height about the meter.

4) Your residual pressure at the utility hookup at your demand gpm is your starting point for design. Say that's 60 psi. Then your fixtures need a certain minimum pressure to work as designed; say you want to provide each fixture with 40 psi at its rated flow rated. The difference is your pressure "working budget" for all the equipment in between (and elevation gain), 20 psi in this example.

5) Now a reasonable place to start the design is to allocate some fraction of that pressure budget just to the meter and the 600' water lateral. Say you choose 10 psi. Then you need to pick a meter size that will drop quite a bit less than that for your demand gpm (there are charts from the meter manufacturer), say you keep it to 4 psi. That leaves you with 6 psi allowable friction loss on your 600' lateral.

At this point, you can go to a pressure drop calculator like this one:

http://irrigation.wsu.edu/Content/Calculators/General/Pipeline-Pressure-Loss.php

It has a "minimum pipe size function" that is perfect for this problem. If I pick 20 gpm as the demand (totally made up, maybe that's too high), and 6 psi (also made up) as the allowable drop, and 600' as the length, it tells me the minimum pipe inner diameter is 1.6". Looking at a PEX dimensions chart, 2" PEX has an ID of 1.653", so in this example if PEX is to be used, then you pick 2".

I understand only from reading here that PE pipe is typically used for a long underground lateral like that, not PEX.

Cheers, Wayne

 

[Sylvan]

I think I said I would NOT use less than 2"

 

[Terry]

I think I said I would NOT use less than 2"

Yes, that makes more sense.

 

[Mattg43]

Thank you gentlemen! Terry, that chart with the PEX listed is great, I was not sure how this would compare to copper or PVC. I do see that you agree with Sylvan on the 2", but the chart looks like my ~45 fixture should work with 1.5, based on the chart, but is it experience talking here, or just adding a bit of "buffer"?

Sylvan, thank you, same question- is it a code or numbers, or a combination of that with experience that tells me to shut up and run a bigger line?

How an engineer would do this:

1) Determine the peak demand gpm for your property. The plumbing code has a concept of supply fixture units, but I'm not clear on those details and how that translates into gpm. Don't forget irrigation. If you want to have fire sprinklers, that may control the demand.

2) Find out out from the utility the available static pressure, and residual pressure at your demand gpm (or at some higher gpm they choose) that will be available at your meter location.

3) Determine the elevation gains involved. Sounds like in your case it would be conservative to ignore elevation, you don't need to serve any fixtures at significant height about the meter.

4) Your residual pressure at the utility hookup at your demand gpm is your starting point for design. Say that's 60 psi. Then your fixtures need a certain minimum pressure to work as designed; say you want to provide each fixture with 40 psi at its rated flow rated. The difference is your pressure "working budget" for all the equipment in between (and elevation gain), 20 psi in this example.

5) Now a reasonable place to start the design is to allocate some fraction of that pressure budget just to the meter and the 600' water lateral. Say you choose 10 psi. Then you need to pick a meter size that will drop quite a bit less than that for your demand gpm (there are charts from the meter manufacturer), say you keep it to 4 psi. That leaves you with 6 psi allowable friction loss on your 600' lateral.

At this point, you can go to a pressure drop calculator like this one:

http://irrigation.wsu.edu/Content/Calculators/General/Pipeline-Pressure-Loss.php

It has a "minimum pipe size function" that is perfect for this problem. If I pick 20 gpm as the demand (totally made up, maybe that's too high), and 6 psi (also made up) as the allowable drop, and 600' as the length, it tells me the minimum pipe inner diameter is 1.6". Looking at a PEX dimensions chart, 2" PEX has an ID of 1.653", so in this example if PEX is to be used, then you pick 2".

I understand only from reading here that PE pipe is typically used for a long underground lateral like that, not PEX.

Cheers, Wayne

Thanks for the info! I dont know if I can calculate peak GPM much better than a guess at 15-20 as an extreme. With limited people and use, I dont anticipate more than about 10-12GPM, so I think 20 is a safe number. No irrigation requirements, that will be handled via other methods, not through this water line.

With pressure I dont know if I will be able to get numbers until the line is in place from the water company. They did a hydraulic study for me at 2" water line and the only info I received on the report was that they guaranteed a minimum of 35PSI at 1.2GPM at the connection when adding my line to the existing waterline some distance away. This has since changed to a 12" waterline being ran for future expansion, but this will obviously be major work and I dont think I can get numbers. I know other people up the road a ways (not neighbors) that have good pressure, but I dont know the water situation well enough to know how that is handled, as there is a water tower not too far away.

Elevation gain is probably negative, but I have not measured. Assume it is 0 ft and I would bet it will be slightly negative.

Without the above info I am speculating that your guesses are fairly reasonable and accurate with GPM demand, and the PSI drop seems pretty good too - this combined with my lack of knowledge and other posts, makes a 2" line seem like a safe bet.

I guess I know what I will be reading up on for the next few days, thank you all!

Matt

 

[wwhitney]

As to step (2) in my post above, the utility should be able to answer that question based on what they know about their existing system and their design for the extension. But if they are extending a 12" line several hundred feet from an existing location to the edge of your property, it's fair to say that your supply characteristics will match that of your neighbor that is currently at the end of line (assuming the neighbor is on the 12" line).

Then if you are friendly with that neighbor, you could do the following test, assuming you have access to a hose bibb that is near to one end of their service lateral or the other, and can determine the service lateral material (if the hose bibb is at the far end). Put a pressure gauage on the hose bibb, and note the pressure when no water is flowing (the static pressure). [Now optionally skip to the last sentence of this message for a likely accurate enough answer.] Then cause a 5 - 10 gpm flow through the lateral, noting the pressure and the flow rate. [That could be filling a bathtub inside, or it could be running irrigation, or it could be right at the hose bibb if you put together a tee to check the pressure while letting water out.]

Then if the hose bibb were directly on the water main, the second pressure reading would be your utility residual pressure at the flow rate. If it's not, you need to model the frictional pressure loss on the piping between the water main and the pressure gauge and add it back in. Which you can determine by using the pressure drop calculator if you know all the piping details.

And then, of course, adjust everything for any elevation difference between your meter location and the measurements at the neighbor's.

Or if you know you are going to have a 12" line outside your property, you could probably conservatively assume that with 20 gpm flow the water main pressure drop is going to be under 1 psi, and just measure the status pressure and subtract 1 psi (and still adjust for elevation).

Cheers, Wayne

 

[Mattg43]

Wayne,


Good info, and the reality is that your last line is probably the realistic bet!

The people I know further up the road are on the original water line that bypasses my property below, but it will be good baseline for the pressures they keep in the line.

I am actually going to be the only person on the 12" line for a while.

This is a rural county water utility provider, and they have had water lines in this area for decades - but when they originally put in the lines there was a spot where the road split and one side had one house, the other side had about half a dozen - so they ran a single line to the corner of the one home property, and the water line along the other portion of the road.

Now the side where I bought land has a water line sized for a single dwelling a bit over a quarter mile away, and the mail line connects back to the "main road" about a quarter mile on the other side of my property. According to the utility, their "long term master plan" intended to upgrade the main line along the road to a 12" in 5-10 years, but their policy is that if a water line is requested in line with their master plan, they automatically upgrade the section of line being laid to match their future plans, and the other 2 residents in my area have wells - so I will be the only person on this line until they continue with their master plan further down the road in a few years.

Pardon my paint skills, but black is roads, yellow box is my property. Green is current water line, red is new master plan line (which will continue up the road (east, if you will). Blue is what they will be putting in for me until they are ready to continue their master plan line from my understanding.

 

[wwhitney]

So if you know where the water mains are and that there aren't any buried pumps that are going to add pressure, you can get a static reading from anywhere nearby on the water system, and just adjust for elevation to get your static pressure.

Cheers, Wayne

 

[Sylvan]

To find static pressure take the height above the main and times it by .433 lets assume 100 feet which would give you a static pressure of 43.33 PSI If the available pressure is only 60 PSI it will elevate the water to 135.60 feet Not including friction losses

43.33 PSI X 2.31 = 100.0923 is how much pressure you need to just make it to the top with no pressure losses due to friction and head pressure

 

[Jeff H Young]

I would not use any diameter smaller then 2"

based on the info do you have any thoughts as to needing greater than 2 inch? I didn't see any static pressure at meter location and noticed you said you wouldn't consider smaller, but is 2 inch for sure sufficient? I'm kinda guessing even if it was only 25 psi it might be ok running 2 inch, but off a 5/8 meter? but I get nervous on low numbers

 

[Mattg43]

I called the water district person I am working with and asked about moving to a larger meter, as well as if she could tell me exact location they planned on setting the meter, and if they had static pressure numbers for the line in the area. I hope to be able to sit down with them tomorrow to get some more information.

 

[Sylvan]

based on the info do you have any thoughts as to needing greater than 2 inch? I didn't see any static pressure at meter location and noticed you said you wouldn't consider smaller, but is 2 inch for sure sufficient? I'm kinda guessing even if it was only 25 psi it might be ok running 2 inch, but off a 5/8 meter? but I get nervous on low numbers

Of course the meter size would have to be increased considerably for a 2" main

 

[wwhitney]

Of course the meter size would have to be increased considerably for a 2" main

Not necessarily.

If you have a 2" lateral because you want to carry 100 gpm 50' to your building, then yes you need a larger meter that will flow 100 gpm without much pressure drop. But if you have a 2" lateral because you want to carry 20 gpm 600' to your building, then you don't need a meter that will flow 100 gpm, you just care about the pressure drop of the meter at 20 gpm. And a larger meter may cost more.

Note also that the utility connection from the water main (12" line in this case) to the meter may be sized by the utility based on the meter size. So if the meter is far from the water main, that's another factor to consider in the pressure drop calculation.

Cheers, Wayne

 

[Sylvan]

Not necessarily.

If you have a 2" lateral because you want to carry 100 gpm 50' to your building, then yes you need a larger meter that will flow 100 gpm without much pressure drop. But if you have a 2" lateral because you want to carry 20 gpm 600' to your building, then you don't need a meter that will flow 100 gpm, you just care about the pressure drop of the meter at 20 gpm. And a larger meter may cost more.

Note also that the utility connection from the water main (12" line in this case) to the meter may be sized by the utility based on the meter size. So if the meter is far from the water main, that's another factor to consider in the pressure drop calculation.

Cheers, Wayne

Unless there is a lot of pressure I cannot see supplying a 2" line by 5/8 meter.

You will not get proper flow and stagnation is quite possible as not enough volume will be flowing and a severe pressure drop

Of course a 2" meter cost more but how often do you change it? The 100 GPM is at the meter not taking into account the run of the line and the fixture units connected.


Gas line yes smaller meter connection to a larger pipe is fine once you calculate the specific gravity of the fuel and distance

 

[Reach4]

Of course a 2" meter cost more but how often do you change it?

A better question may be how often do you pay for it? Depends on the water folks.

For example, https://www.acwd.org/115/Water-Rates has an every-2-month meter charge of $ 56.61 for a 3/4 inch meter, and $ 255.99 for a 2-inch meter. 2-inch pipe is a one-time cost.

 

[wwhitney]

a severe pressure drop

I have no idea what you mean by this. The meter pressure drop is just going to depend on the meter size and flow through it; the size of the downstream pipe is immaterial.

As to stagnation, either a 2" lateral for 0-20 gpm at 600' is OK, or it's not. The meter size has no bearing on that.

As far as I can see, the physics principles are the same here for gas or water (although the details differ).

Reach4 covered the cost issue, I was referring to recurring charges to the customer, not the cost of the meter itself. Of course, if your utility doesn't charge you by meter size, go ahead and get the biggest meter they'll give you, there's no downside that I'm aware of.

Cheers, Wayne

 

[Jeff H Young]

A better question may be how often do you pay for it? Depends on the water folks.

For example, https://www.acwd.org/115/Water-Rates has an every-2-month meter charge of $ 56.61 for a 3/4 inch meter, and $ 255.99 for a 2-inch meter. 2-inch pipe is a one-time cost.

Yes the few projects where It came to my attention (as meter prices aren't much concern to me) they have a fee upfront and then your monthly bill you pay more monthly forever and the ones I've heard were significant no 5 bucks a month.
My thought is that depending on demand increasing the supply line size may be enough. but a 5/8 is a puny size on a 3.5 bath house it seems.

 

[wwhitney]

FWIW, my utility use Badger Recordall meters, and from their published data, at 20 gpm their meters will drop:

Model 25 5/8" 6 psi
Model 25 5/8" x 3/4" 4.6 psi
Model 35 3/4" 3.3 psi
Model 55 1" 1 psi
Model 70 1" 1 psi

Cheers, Wayne