Choosing the Right Flow Totalizer

I don't know how to calculate from from raw pressure.

For water, a magmeter is ideal (unless it's deionized water).

Most magmeters have similar ranges over which they can make a measurement. These numbers are for a Siemens magmeter:
- Min. measuring range: 0 ... 0.25 m/s
- Max. measuring range: 0 ... 10 m/s

A nominal 1" (DIN 25) sized magmeter will measure from ~11 liters/min (~2.5 gpm) to ~250 liters/min (~85 gpm)

Most smart magmeters have a totalizer built into them. Use the mag for flow rate and flow total.

If you can measure the velocity of the water in the pipe, do it. Multiply this by the pipe cross-sectional area and you get your volumetric flow rate. Finally, size your meter at least 50% higher.

I paid a service $250 to come out and measure an unknown flow with a clamp-on ultrasonic flow meter. The deal was that they had to get a valid reading, or no charge (I'm suspicious of non-contact technologies). But the device worked and I got a readings in both velocity and volume from that model clamp-on flowmeter that were needed to size a permanent flowmeter.

The service was offered by the rep who sells the clamp-on flowmeter.

The pressure in the pipe will not suffice to calculate the flow rate. You don't know the pressure downstream of whatever the pipe is connected to, nor the losses. However, it is unlikely that the water velocity will be higher than 10-20m/s or noise and cavitation will be an issue. So let's assume 10m/s, then the flow rate is vA where v is the velocity, 10m/s and A is the cross sectional area of the pipe. This gives 5 L/s flow rate.

50USG/m is about 3.2 L/s so it could be a little undersized. However, it might be fine if your flow rate is less.

Just ball park figures so do as suggested and get a measurement if you can.

Cheers,

Frankston

Thanks all of you guys, it is really helpful all your comments.