# Do municipal water meters measure entrained air?

1. ### gary.walker2

1
I have just now seen an advertisement on tv that claims to save up to 40% on residential water bills by inducing the meter to not measure the volume of air bubbles represented by entrained air in the supply line. This device is to be placed immediately DOWNSTREAM of the meter and presumably somehow compresses the bubbles upstream of the meter! Not being an engineer but with average knowledge of homeowner issues and a desire to keep my water bill down, I'm curious. Does this device make physical sense. Could entrained air bubbles really significantly affect the measured volume? To whoever wants to respond I'll be grateful and will answer questions about the claims although I think I've stated it succinctly. gw

### Staff: Mentor

No, that isn't possible. I don't know if it can do what it says to entrained air (unlikely), but there isn't that much entrained air in a domestic water system to begin with.

3. ### brewnog

2,793
At the kinds of flow rates I'm interested in when testing engines, entrained air can make a significant (perhaps a few percent) difference to the true reading. The idea that I can fit something downstream of this (rather than spend thousands of pounds on a fancy water meter) is ridiculous, and would make bugger all difference for a domestic supply anyway.

File under C for Cobblers.

4. ### dr dodge

336
upstream, maybe downstream, no way
I can't imagine there is actually that much air

I would be concerned that all it was doing is slowing down the flow, making it appear like your getting the same amount of water for less \$, but in actuality slightly reducing the water you use.

If you are serious about saving water and money there are better ways. improved showerheads, always wash full loads of clothes, hand wash dishes, toilet water reductions, etc
we even re-use the water that I get from the de-humidifyer heating the house for laundry water (we get ~5 gallons per day)

don't skimp oin the showers, though, you can lose friends

dr

5. ### waterman

1
First of all, there is a lot of air in domestic waterlines, hence "air vaccuum assemblies" are installed in high points of waterlines. But for the average homeowner, this meter air strainer would probably only be the most beneficial if you live on a hill or higher than the watermain you're connected to.