Low Flow Meter

[z8e]

To keep the jurisdiction happy, I need to measure flow either going into or coming out of a large septic tank. The flow is going to amount to a few to several hundred gallons per day--not much. All the meter guys say the accuracy goes to he11 at low flows. Does anyone know of an inline flow meter that would be accurate at low flows?

4" diameter pipe.

Thanks.

 

[dicksewerrat]

Can you meter the water going into the bldg? See if they will accept that.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[rjanoch]

if the tank is empty to begin with, and the volume going in will be less than the tank volume....you could measure the level in tank at the beginning and end and calculate the storage volume.

 

[bimr]

If you want to spend the money, an Endress + Hauser mag meter will provide you a flow meter with less than 1% error.

Howeveer, you will have to install the meter such that the metering point is full of water at all times.

 

[Watthour]

A flume is almost definitely out of the question.

 

[greenone]

Actually, I have acquired a client with the same need this last week. We don't want to use the water meter input reading, as quite a bit is used for landscaping, domestic and into the product; we need to meter just the effluent from a settling tank to the sewer.

z8e, if you find one that is suitable, I would appreciate your posting the info. So far, I haven't found one.

 

[bimr]

greenone,

It is common practice to install multiple water meters. You can have one meter for the sanitary service and a second water meter for irrigiation purposes.

You do not have to pay the sewer charges for the water used on the irrigation meter.

 

[greenone]

Bimr-yes, thanks, but actually, quite a bit of water goes out in the product, through ways other than the sewer or landscaping (our estimate for last year was a couple thousand HCF loss.)
An effluent meter would be the fairest way for both the utility and my client.

 

[bimr]

Water is still relatively inexpensive. If water costs $1 per thousand gallons, you are not talking about much money.

Assume couple thousand HCF loss is -
2000 * 100 CF *7.48 gal/CF = 150,000 gallons

Is that correct? your additional water cost is only $150 per year?

There are gravity flow meters available with that accuracy. However, the meters are for larger flows (greater than 15 gpm) and larger diameters (greater than 12") with that accuracy

Again, you would be best served with a mag meter. Magmeters have that accuracy.

 

[tkall]

If the regulators are really going to make you do this the only practical way is with a pump. In my experience a flow meter for this application will be expensive and inaccurate. A small pump chamber at the end of the tank will allow you to count cycles and multiply by the volume per cycle. Anything else seems like snake oil to me.
Tom

 

[SteveWag]

I would agree with “tkall” and would add that a small pump with a 1 ¼- inch discharge would lend itself to the use a line size mag-meter. The meter would indicate rate of flow and totalize (integrate) and provide a read-out. This will give a readout that the Utility is happy with. I have found that counting pump cycles and doing some math is beyond some data readers abilities.
Steve

 

[greenone]

Hi bimr-here in CA Bay area, water is quite expensive-about $4 for 748 gallons. But it's the sewer charges that are driving my client's issues-there are surcharges based on various constituents present in the effluent. By showing the utility the correct reductions of water to the sewer, I was able to reduce my client's sewer bill by about $75,000.