View Full Version : size main water supply line
11-18-2004, 01:17 PM
:confused: We are building in TN. The water pressure at the road is 130psi. Our line will be approximately 600 feet long with a 100 ft elevation rise. The lot is also fairly wooded. We are building a 2900 sq foot house with a full unfinished basement. The house will have 3 full baths. My question is what size line would be best to run from the road. My builder has recommended a 2 inch line due to the gasket fittings. I am concerned with stagnant water in the line. Is this a valid concern. If so what size line would you run? Would you advise schedule 80 or 40 pvc?";
Gasketed fittings will have not effect on the water volume delivery. I would use 1 1/2" sch. 40 PVC, although if you use gasketed pipe it will be a lower class than sch. 40. Be sure to install a pressure reducing valve at the house, not at the meter.
11-18-2004, 09:43 PM
I ran an online calculator on this. I assumed 12 gallons per minute peak demand. For schedule 80 1¼" pipe, it gives velocity of 3 feet per second, which is good ( not recomended to exceed 5) and a friction loss of 7.6 PSI, which would be in addition to the 45 PSI loss for the 100 ft. elevation.
11-18-2004, 10:51 PM
I'm thinking a 1" meter and at least 1-1/2" pipe.
If your'e worried about stagnant water in the line, keep in mind that the street may have 8" mains. A 2" line would be fine too.
A friend of mine ran 2" and added four yard hydrants down the driveway to the home for watering the yard.
11-19-2004, 06:30 AM
Around here, the base charge for service (the amount you pay for having service - i.e., no water usage) is based on the size of your potential demand - the size of the supply pipe. So, double-check your supplier. You want a supply line big enough to satisfy your needs, but you don't need a perpetual excess cost, if they do it thatway where you live.
I ran into this when a friend bought a condo with sprinklers. Each unit had a 2" line. Even though it was basically a 2-bedroom small house (for practical purposes), the water district charged them a significant fee each month for the potential use of lots of water based on the 2" supply line. Much more than say a 1" supply line.
11-19-2004, 11:34 AM
Wow you all have been very helpful. My builder recommended the 2 inch line due to the gasket fittings. He said less of a chance of leaking. Is this true?. It sounds like the 2 inch pipe is not as thick if it is lower that schedule 40. We do have a rockie area to go through. I know about placing sand in this area which will help. Any thoughts
11-19-2004, 02:02 PM
I ran an online calculator on this.
Jimbo is this calculator available for anyone to use? Can you share the Web address?
11-19-2004, 05:45 PM
The integrity of the gaskets has nothing to do with the size of the pipe.
11-19-2004, 08:18 PM
although if you use gasketed pipe it will be a lower class than sch. 40. .
hj I realize the integrity of the gaskets has nothing to do with the size of the pipe. I should of started a new paragraph. I just did not realize the 2 inch was a lower class than sch 40. So that makes me even more concerned about using this in a rocky area.
11-19-2004, 10:35 PM
The idea of being charged for "potential" water use is something I have never heard of for domestic water, and it seems a poor way to do business. If you had a 1" line and ran it 24 hours a day, you'd pay less that someone with a 2" line that ran water only once a week? Water is usually sold by amount actually used as recorded by a water meter. The only exception I know of to that is irrigation water that is delivered via a canal. The you will pay for the acre feet that you are entitled to, even if you don't use it. I think the advice given has been pretty sound. Don't go with minimum size, but no need to overkill either.
11-20-2004, 07:01 AM
I believe that here the "hook up" fee for a new meter is based on the meter size, not the size per se of the pipe running up to the house. The theory is the utility has to have the infrastructure to support the installed equipment. SO , if you put in a 2" meter they can't assume that some day you or a future user would not demand the full amount of water that a 2" meter will provide. I think this was why Terry recommended a 1" meter feeding a 1½" pipe. The 1" meter will provide all the water this customer needs, and within reason it is always preferred to upsize pipe on a long run to minimize the friction loss and reduce water velocity. Budget concerns then become the decision maker between 1" pipe, 1¼", 1½", or 2".
11-20-2004, 08:42 AM
I believe the correct way to size this/any pipe is to actually know the peak demand you need to cover at the pressure you want available at the elevation you have to provide the water to. So do the math or make them do it. Especially if you have any large whirlpool jetted type tub and/or mulriple head showers etc.. Some large tubs flow at upwards of 18 gpm and multiple head and/or shower wall showers can get very high demand and that doesn't include water for other uses.
Once I knew how many gpm I need, with some for future use if needed, I'd select the proper size of 200 psi rated polyethylene tubing and run it in one continous roll. That eliminates all joints but one on each end. It commonally comes in up to 1000' rolls and any well/pump supply house has it (or can get it) and the fittings. It is used to hang up to 1.5 hp submersible pumps in wells to 600' deep (here) and has excellent flow charcteristics. The trench prep and backfilling is the same as for any other plastic; protect from sharp edges and allow for expansion/contraction, which is very easily done by 'wandering' the run in the trench instead of 'straight as an arrow'.
I wouldn't want a joint every 10-20' over a distance of 600' regardless of the type; gasketed, oring, threaded etc..
Quality Water Associates
11-20-2004, 10:12 AM
They meter the water, and you pay for that used, but, you also pay for the potential demand - i.e., the size of the supply in that community (Hudson, NH). Now, I'm not sure if they had a 2" meter, it may have been a difference for the meter vs. the actual supply line, but they also did have 2" lines into the condo for the sprinklers. Seems to me that would have been a problem with stagnent water, but maybe they were dry until needed. That's another story altogether, though.
11-20-2004, 10:16 AM
This is a good point, Gary Sl.
I went back to the calculator, and actually for 20 gpm in 1¼" pipe, the velocity would be up to 5, and the pressure loss over 600 feet would be about 20. SO this would still be acceptable, but I think the case is made to go with 1½" MINIMUM. I think poly pipe also has slightly better numbers on these calculations than sch. 80 PVC.
He may be referring to the way they charge here. All water is charged by the actual usage, but each sized meter has a different minimum usage. If the actual amount used is less than that you are charged the minimum. If you go over, you are charged the actual amount. In addition, they sometimes have a premium that they add if you exceed a certain usage for that meter size. For this reason some apartment complexes that have multiple meters feeding a common loop, will have some of the meters shut down and removed to eliminate the minimum fees for those meters, especially if the flow pattern is such that the other meters measure the bulk of the usage and those meter lag behind and are subjected to the minimum fees.
11-21-2004, 10:10 AM
jimbo, PE has the better flow rate. And with his 100' elevation, his install is much different than a 500' well which is straight up and 5 times the head he has. Usually we only use 1" PE from the correctly sized pump to the pressure tank which will feed a 2 story house all the water it needs at 60 psi. All submersible pumps have a 1.25" outlet but we reduce that to 1" in most installs. In this case he only has a 100' of elevation (equal to a very shallow well) plus the height of the highest fixture in the building plus the friction loss in 600'. He doesn't need more than 1" for the average 3 bath house (without large tub or multiple shower head showers) so 1.25" would be oversized one size which makes 1.5" overkill. He has 138 psi at the street. I vote 1.25" if he needs more than 15 gpm.
Quality Water Associates