Hi All – first post here. I’m having a home (3BR/3BA) built on our land in NC and the run from the water meter is 550′. I intentionally purchased a 1″ water meter for this reason.
I recently discovered that my builder’s plumber installed a reducer at the meter down to 3/4″ and ran 3/4″ the entire 550′ run. A wildly odd decision if you ask me.
I know someone will ask if it was specified. It wasn’t – I didn’t think I needed to because the meter was 1″. I didn’t think they would intentionally step it down.
The plumber is telling the builder that 3/4″ is code up to 4BR. Specifically: “Size of water service pipe: The water service pipe shall be sized to supply water to the structure in the quantities and at the pressures required in this code. The water service pipe shall not be less than 3/4″ in diameter.”
Am I at risk here of pressure issues? Some math and calculations show me that I will see a massive drop at higher flow rates (like 10 GPM). I believe specifically the pressure drop is on the order of 4x that of 1″ pipe due to frictional losses during flow.
Note, the upcharge and “change order” is wildly prohibitive to have them fix this problem. This alone blows my mind because it’s laying in an open hole. Would be pretty easy but of course I can’t touch it.
I called the inspectors office, and they are telling me there is no provision in the code to account for pipe run length.
Am I overthinking?
Replies
No, you're not overthinking. For a 550′ run, using 3/4″ pipe will likely lead to significant pressure drop, especially at higher flow rates. Upgrading to 1″ pipe is ideal for maintaining adequate pressure throughout the home, given the long distance.
"shall be sized to supply water to the structure in the quantities and at the pressures required in this code."
If the pipe is in the trench, get the inspector on site and ask for a demonstration of the capability to deliver the rated volume and pressure at the interface to the house.
https://up.codes/viewer/virginia/va-residential-code-2018/chapter/29/water-supply-and-distribution#29 Your state codes may vary a bit. Code has design numbers based on service points. (hose bibs, washing machine. sinks, toilets, etc)
Part of the puzzle is what the local utility maintains as water pressure. Sure looks to me like 550 ft of 3/4 pipe would loose 55PSI at ten gpm, while 1 inch pipe would loose 16PSI. If the pressure from the system is high enough to provide adequate flow with 3/4 inch feed, you likely would want a pressure regulator on the system.
https://toolbox.tlv.com/global/US/calculator/water-pressure-loss-through-piping.html
You are correct to doubt. This is a math problem, find a good online calculator. You need to know supply PSI and GPM demand. You already know your pipe type/size (make sure I.D. is right). It sounds like code requires a minimum GPM and PSI, so might have to look that up. Consider the demand that you or a future owner may have if you are irrigating lawn, watering a garden, or other high output outdoor needs.
I don't know your builder/plumber, but the cost for 3/4" is much less than 1", that could have been a factor.
Without doing the math I can say that I personally would be considering 1"-1.5", depends somewhat on your supply pressure.
Thanks everyone. I spoke up enough that ironically, after the inspection, the builder and plumber had a magical “change of heart” and agreed to swap out to 1”. I had to supply the line but no other charge other than that. My intuition says the inspector noted it and heavily suggested it be swapped out. I appreciate the feedback. My math wasn’t mathing as well.
So a great Thanksgiving blessing