Water meter inlet sizing and how it affects WH tank output

Our community is having all the water mains replaced. They are woefully undersized at 4" so they're digging up the streets and going to a 8" line.

As part of this project, they're running new service to each house in the community. They're also installing water meters. Previously no one was on a water meter here. You should also know that the community has separate water supplies for domestic vs irrigation water. The water meters are to be installed only on the domestic water supply.

The problem is, the HOA has decided in its infinite wisdom to install 3/4 inch water meters on the domestic supply. They claim that because this is for domestic water only, there should be more than adequate pressure. They are quoting a flow rate of 30 gallons per minute at 50-60 psi via an adjustable regulator.

The old 4" water line with no meter to the house had 85 psi.

Our house is 5 bedrooms, 4 baths with two laundry rooms. We have multiple head showers in one master and a large 120 gallon tub. If we have one or three showers going at the same time or even with a dishwasher in addition, are we going to have adequate water pressure? We will be installing two 75 gallon WH's, one on each side of this ranch style house so that each WH supplies one side of the house.

My contractor thinks that the 3/4 inch line coming in from the meter is likely too small for our needs. But the HOA maintains that it should be more than adequate and is not willing to upsize the meter for us. Thoughts?

A 1" line will give you the same water pressure, but more water volume. Maybe this is the reason the HOA is going from 4" supply to 8".
I agree with your plumber, for a large home it should be 1".

UPC Water Pipe Sizing

Turn the regulator up to 80 psi. If you overdraw the capacity, then the dynamic pressure may drop to the original 50 psi. The size from the main to the meter, and the meter, is sometimes irrelevant, because it is usually fairly short. The size from the meter to the house and through the house is critical.

hj said:

Turn the regulator up to 80 psi. If you overdraw the capacity, then the dynamic pressure may drop to the original 50 psi. The size from the main to the meter, and the meter, is sometimes irrelevant, because it is usually fairly short. The size from the meter to the house and through the house is critical.

Click to expand...

The distance from the new main 8" line to the backflow device and regulator is about 30 feet. The distance from that point to the water meter is quite a ways - about 120 ft or more. I suppose we could run a 1 to 1 1/2 " line from the regulator/backflow device to the water meter, but at the end of the day that water meter is going to only put out at a 3/4" size.

The quoted output from the meter is 30 GPM at 50-60 psi.

WHen the restriction is short, it doesn't have as much effect as when it continues for a distance. Running a larger pipe from the meter will cause the water to speed up through the meter (when required) an slow down through the pipe to the house...so, it would be nice if the water company could run larger pipe to the meter as well, maximizing your ultimate capacity with that meter. IOW, the size of the pipes make a bigger difference than the size of the meter, but the size of the meter will have some restriction.

jadnashua said:

WHen the restriction is short, it doesn't have as much effect as when it continues for a distance. Running a larger pipe from the meter will cause the water to speed up through the meter (when required) an slow down through the pipe to the house...so, it would be nice if the water company could run larger pipe to the meter as well, maximizing your ultimate capacity with that meter. IOW, the size of the pipes make a bigger difference than the size of the meter, but the size of the meter will have some restriction.

Click to expand...

Got it. That makes sense. The run from the street to the backflow device is fairly short (about 30ft or so). I have no control over that. But from the backflow device at the lot line to the water meter by the house is at least 120 ft and it has been suggested I run at least 1 1/4 if not 1 1/2 inch line.