# need to know flow rate

I have 5/8" PEX piping (I.D. .475") throughout house. Am connected to city water supply (@ 40# psi) all new PEX pipe, all new valves....no leaks

In April, 57,000 gallons reportedly flowed thru the house. In May, 37,000 gallons reportedly flowed thru the house. In June, 11,00 gallons reportedly flowed through the house.

History, In January, February, and March...only 2000-3000 gallons flowed each month. From July to Dec, the flow rate was back to 2000-3000 each month.

Based on the 5/8" PEX pipe diameter, with the 40 psi pressure, how many gallons is possible to flow in one hour? With a 30 psi, whats the flow rate per hour? With a 50 psi, whats the flow rate...in gallons per hour for the 5/8" PEX?

How do I figure the flow rate, (gallons per hour) coming to/through the 5/8" PEX depending only, on knowing the cities psi at the time? The psi could be a variable.

• While I think there's room for working through the actual calculations, the most likely situation is that you have a burst / leaky pipe between your residence and the water meter. Depending upon how deeply the line is buried and ground conditions, you may not see the leak from above. Also worth noting that you may have a different pipe material from the meter to the house.
– user16
Commented Feb 4, 2019 at 2:12
• Thnx. had the entire home repiped in Jan 2018, city inpector signed off with no leaks. all new piping and all new valves. avg usage 2000 gal prior and after unusually high bills of April, May, and June......why? No leaks, normal usage. Commented Feb 16, 2019 at 9:09

The easy way is to put a big bucket under each water outlet in the house and turn every one of them on at the same time, and let them run for exactly one minute. then shut them all off and measure how many gallons of water you got.

To do this, you turn on all the faucets, shut the main supply off, position your buckets, and turn the main on for one minute, then shut it off again.

When you do this experiment, you should also have a pressure gauge near the main valve so you can repeat the test for different values of the source pressure.

If you need to convince someone else (especially an engineer ;-)) that your water billing is in error, you'll have a much easier time using experimental data than by theoretical calculations!

• thnx. I did that and timed exactly one gallon per minute. multiple tests, same results. one gallon per minute. Commented Feb 16, 2019 at 9:11

Instead of going to all the hassle of using all the taps and 1 minute of flow etc.

Consider closing the main isolating valve to the property overnight for 8 hours or 6 and see if the main meter records a reading - will at least confirm any leak upstream of the property.

Did exactly that on a house I had and there was a leak. Then the water people replaced the supply pipe for free ! Special offer to reduce leaks...

• that test, conducted by me with a city water employee, showed all flow stopped with the valve closed. multiple tests, same result..no leaks. thnx Commented Feb 16, 2019 at 9:13

Not sure how your setup works, but here a city employee has to physically read the meter at your location at regular intervals.

What happens in practice is that instead of reading the meter monthly and sending you a bill based on actual consumption, they work on historical averages when they bill you and only send someone to physically read the meter once or maybe twice a year.

If the meter reading is significantly higher or lower than what it was predicted to be using monthly historical average consumption, they make a once-off adjustment (or split over two or three months if it is a very large discrepancy) so you get a high bill or " zero use " bill for a month or two before the consumption figures return to something "normal".

In the same way in some suburbs the metres get read so rarely that many people get a nasty surprise when they sell a property and are suddenly told they have to pay off an enormous water bill.

In some areas, city officials have admitted that they have a problem and are allowing property owners to send in meter readings with photographic/video evidence if they want to avoid the "monthly average" billing.

If your city system is the same, It might just be that the inspection after your re-pipe is the first time in a year or more that someone actually read the meter and there was a large discrepancy - e.g. maybe you filled a swimming pool or had long term guests or something in the last year or so that meant your consumption was higher than predicted for several months.

• This exact thing happened to me with an electric bill for the first month in a new apartment. Commented Aug 18, 2020 at 18:34

Instead of coming up with values that can be explained away, you should have concrete evidence on your side. Most pipes coming from the city water supply meter to your house are 3/4" (check yours first). Install or have a flow meter installed directly off the water meter supplied by the water company for numbers that can't be easily refuted by the water company or you, should there be an underground leak (since the values went back down isn't the case here). Everything from the water companies meter to your house is the responsibility of the home owner so as long as you follow your areas building code there wont be a problem installing it. A lot cheaper than an additional 34k gallon water bill. You should also be able to check the water companies meter yourself by looking at it.

FLOW METER,

https://www.amazon.com/DAE-AS200U-75-Couplings-Measuring-Gallons/dp/B06XJZSWQ2/ref=sr_1_7?s=industrial&ie=UTF8&qid=1549247199&sr=1-7&keywords=flow+meters

• yes, I had a water meter installed downstream of the city's meter, two months before the unusually high water bills of April, May, and June. My meter showed only the normal usage but the City of Houston IS NOT HEARING IT. I know their meter is reading accurately, because I always get billed for 2000-3000 gallons every month. So what caused the meter to read 57,000, 37,000, and 11,000 for three months, then magically revert back to the 2000 gallons? No changes have been made on my side of the meter.. I made all my changes prior so that I wouldn't have high water bills. Commented Feb 16, 2019 at 9:21