Water service line size for 130' elevation gain, 550 ft length

[Chuck17]

Hi, I'm in the process of building a house, and am looking for recommendation for the right water service line size from the road. I'm up on a pretty good hill, about 13o' feet up from the meter, and 550 ft in length from meter to house. The municipality thinks I won't have to pump the water to the top,
they said it should have adequate pressure. I don't know what pressure will be at the meter. My contractor recommended 2" pipe from the meter to the house, while the guy trenching for the line recommended smaller, like 1" or less. From research I've done, the bigger pipe looks like it will handle it much better. My specs are: kitchen sink, 2 bathroom sinks, 2 toilets, 2 showers, laundry sink, washer, a couple of hoses outside.

 

[Terry]

1-1/2" may do it.
I would not do 1". I did a 350 foot line with 1" one time, and was surprised at how much friction loss I was getting. Once was enough for me to figure that one out.

0.433 psi per ft of elevation.
56.29 PSI reduction. You may want the pressure booster too.
(edited after reading the post by Reach4 below)

 

[Sponsor]

 

[Reach4]

I'm up on a pretty good hill, about 13o' feet up from the meter,

You are going to lose almost 60 PSI just from the altitude change, and then there will be loss from flow. Unless the pressure at the meter is high, you would need a booster pump.

The municipality thinks I won't have to pump the water to the top,
they said it should have adequate pressure. I don't know what pressure will be at the meter.

If they can give you over 90 psi at the meter, you can probably get by without a pump. Ideally they would be giving you even more.

 

[Chuck17]

Thanks! Another thing I was wondering, will the drop in pressure due to elevation change be more with a bigger pipe? Or is it a constant? Same loss with 1" vs 2"?

 

[Terry]

Thanks! Another thing I was wondering, will the drop in pressure due to elevation change be more with a bigger pipe? Or is it a constant? Same loss with 1" vs 2"?

Pipe size should matter for pressure loss or gain, only friction. Once you bury the pipe, you're stuck if the small size is an issue.

 

[Reach4]

Thanks! Another thing I was wondering, will the drop in pressure due to elevation change be more with a bigger pipe? Or is it a constant? Same loss with 1" vs 2"?

Constant.

So the drop due to flow gets added to the drop due to elevation.

https://www.engineeringtoolbox.com/pvc-pipes-friction-loss-d_802.html for the dynamic drop. http://www.kylesconverter.com/pressure/feet-of-water-to-pounds-per-square-inch for the elevation drop. When the water does not flow, the dynamic drop is zero, but the elevation drop is constant.

Note polyethylene ASTM D2239 pipe and PVC pipes is larger inside than copper or CPVC or PEX for the same nominal size.

For 500 ft of pipe, the effects of thermal expansion need to be considered.

 

[Chuck17]

Appreciate the education. This is all new to me. I've got one more, would a 2" line be preferred over a 1-1/2" line in this case? Would 2" be overkill? Sorry if this a stupid question, I just want to make sure it's done right. Thanks for all the help guys!

 

[Terry]

It doesn't hurt to go big. If there is also a concern with fire protection, I would see it as a plus.

 

[Reach4]

I would plug maybe 15 gpm into the tables, and see if it is worth the extra materials expense. If you have only 30 pounds of pressure at the house due to elevation, 2 PSI less drop is worth more than if you would have 50 PSI at the house.

A house seldom uses 10 gpm, but maybe the sprinklers would change that.

 

[Chuck17]

So I’ve found out the neighbor has 95 psi at his meter, municipality said I should have the same pressure as them. Just from the elevation, I’m looking at losing 60 psi. Should I go with the 2” or the 1-1/2? I may not be reading the calculators right, but I will lose less pressure over distance by going with the 2 inch? Around 2 lbs with the 1-1/2 inch versus .5 lbs with the 2 inch...?

 

[Reach4]

I may not be reading the calculators right, but I will lose less pressure over distance by going with the 2 inch? Around 2 lbs with the 1-1/2 inch versus .5 lbs with the 2 inch...?

I just remember that 60 PSI is about 140 ft. Your elevation change is less, but if you have a second story, you would be up to 140. So it is a handy round number for you.

At zero flow, there is no difference in pressure loss. During a 2.5 gpm shower, there would be a fairly insignificant difference.

Have you priced the difference? I think that would be a big factor. As Terry points out, if in doubt, go bigger. It is better to have bigger than you need than smaller than you need.

There are rules of thumb about an elbow being equivalent to adding x feet of pipe. I will let you look around. Is x=5? I could look around, but you might want to do that.

I would be looking at the ASTM 2239 poly pipe. Is that what they had in mind? Does the city permit that? Most would.

https://terrylove.com/forums/index.php?threads/black-poly-tubing-for-potable-water.54313/
http://www.performancepipe.com/en-us/Documents/PP814-TN Thermal Effects.PDF

 

[LLigetfa]

It is possible that the 95 PSI static pressure could drop during high GPM draw due to resistance on the city's line. 35 PSI is nothing to write home about. I certainly would not be happy with such low pressure. If you want to boost the pressure then you have to either have a cistern or get permission from the city to draw a vacuum on their line. EDIT: at that elevation the effect on their line might be minimal.

If you put in a cistern then a much smaller line would not matter as it would have all day to top it off and the GPM doesn't have to match sporadic consumption.

 

[LLigetfa]

During a 2.5 gpm shower, there would be a fairly insignificant difference.

...until someone flushes a toilet and/or the washing machine goes to a fill cycle.

 

[Reach4]

If you want to boost the pressure then you have to either have a cistern or get permission from the city to draw a vacuum on their line.

From a logical and physics point of view, I think it would be impossible to draw a vacuum on the city's line from 130 ft up. This is not to say that a city would see it that way.

I think 30 PSI is fine, but I know that there are a lot of people who think otherwise. That said, I do set my water pressure to 37/57. But when it was 30/50, I did not notice a problem. But since you don't have that much margin, I think that further argues for the 2 inch.

There is one more thing to consider: for comparing water pressure with the neighbor's house, you want to compare vs the elevation of where he took the 95 PSI reading, because he may also be elevated some compared to the water meter.

 

[Chuck17]

So, if I wanted to boost the pressure, and didn’t want to use a cistern, I would use a pump? Pump in the house? Or halfway down the hill? And if I pumped, I would still want to use the bigger water line?

 

[LLigetfa]

With a pump at the house and without a cistern you should use a 2 inch line.

 

[Reach4]

I think you should use the 2 inch poly and plan for no pump. Those remain an option to add later, except that if you put the pump part way up the hill, you would want to run the power wires for the pump house while you are burying the pipe. If you were sure you were going to have a pump, I would go smaller pipe, but I really think a pump is a maintenance item that you don't need.

I would also make your indoor plumbing large enough. I like home-run hot pipes for faster hot water without requiring recirculation, and branched off cold for simpler piping.

A pump could be half way down the hill or at the bottom of the hill. However I think it could easily go in the house. That avoids any concern about freezing. Outside of the house would be quieter, but I doubt the sound would be bad. Just leave some space, just as you may leave space for a water softener or even a carbon tank. 30PSI is enough for backwashing a softener or carbon tank also. A softener might use 2.4 GPM to backwash in the middle of the night.

 

[LLigetfa]

If you were sure you were going to have a pump, I would go smaller pipe

If you look at most pump installs, the inlet pipe is almost always larger than the outlet. This is because friction loss on the intake side is more detrimental. I have to assume reach4 meant to only have smaller pipe on the upstream side but perhaps not.

 

[Reach4]

If you look at most pump installs, the inlet pipe is almost always larger than the outlet. This is because friction loss on the intake side is more detrimental. I have to assume reach4 meant to only have smaller pipe on the upstream side but perhaps not.

I meant the 600 ft of pipe. If you are feeding a pump, 4 extra pounds of loss would not be a big deal. It is probably not that big of a deal without a pump, but 2 inch would be better.

A good price for 1.5 inch ASTM D2239 SIDR 11.5 160 psi poly pipe might be $550 for a 600 ft plus tax. 2 inch might be $780 for 500 ft . Delivery to the site rather than the store would cost more, and maybe there is no nearby store. Coils of 1.5 inch might be 300 ft and coils of 2 inch might be 200 ft. So more couplings with 2 inch.

Your typical booster pump is getting fed with low PSI or even negative PSI. In this case, the pump would be being fed with helpful pressure.

 

[Jadnashua]

30psi delivered in the house would not be my preference. Certainly, it works. I lived in the middle east for awhile, and they put a tank on the roof, then we only had gravity feeding things...maybe 5-10psi...it made taking a shower and trying to rinse off a new experience. Millions if not billions of people would be ecstatic with 30psi...we're spoiled. I'd try to minimize the pressure loss, and maybe provision to add a booster pump if you decide it will make your life better...it's best to plan for that in the build rather than trying to find room and reconfigure later, even if you don't install it initially. Many people prefer the pressure much higher, but it is an additional cost.