H2Flow Meter

[JamesW]

Since you have at least 3 different ways to calculate the flow, you should log all three over time and then run a statistical analysis on the readings to see how well they match by calculating the standard deviation.

I would suggest a maximum standard deviation of about 4.25 for a mean of 170 GPM.






y =0.0938688 e^(-0.0276817 (x - 170)^2)

y=0.0938688 e^(-0.0276817 (x - 170)^2) - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

For example, if you have these readings, the standard deviation is 4.55, which is acceptable.

171.139, 168.262, 172.618, 165.91, 164.537, 173.317, 170.344, 172.461, 170.075, 167.758, 163.227, 180.169, 177.31, 174.138, 169.025, 169.166, 175.105, 167.592, 172.223, 172.856, 162.286, 172.131, 167.155, 170.048, 171.169, 174.637, 175.298, 159.688, 175.546, 171.368

Standard Deviation Calculator - Sample/Population

Use this standard deviation calculator to find the standard deviation, variance, sum, mean, and sum of differences for the sample/population data set.

www.standarddeviationcalculator.io

For example, if your readings are 135, 155, 180, 145, 170, 160,

Standard Deviation is 16.355 and the mean is 157.5 GPM.



This would be an unacceptable data set and you would need to address the outlier variables like the 135 GPM reading.

The mean needs to be the minimum required flow rate and the standard deviation should be less than 5 GPM.

 

[JPMorgan]

Remember that the BW flow meter is installed incorrectly, as it is supposed to have a straight length of pipe that is 5x pipe diameter (15") upstream from the flow meter (and 10x pipe diameter down stream). The pool company installed it right next to the h2flowmeter, so my guess is that the 135 gpm reading on the BW flow meter is incorrect as it does not have 15" of straight pipe upstream and may be impacted by turbulence from the h2flowmeter. We'll start by affixing that new label to the h2flowmeter when it arrives and see where we are. If we get the 170 gpm we need, then no need to re-install the BW flow meter. If we are still under the required flow rate, I might have them clean and re-install the BW flow meter temporarily in the return line after the filter to see if we get a different reading there. Will update when we get to that point. Thanks.

 

[JPMorgan]

Here is the section of pipe after the filter where I would have the BW flow meter installed if necessary in order to double check the reading we are getting at the h2flowmeter. There is adequate pipe length in that section to meet the requirement for straight pipe lengths before (30") and after (15") where the flow meter would be installed.

 

[mas985]

Remember that the BW flow meter is installed incorrectly, as it is supposed to have a straight length of pipe that is 5x pipe diameter (15") upstream from the flow meter (and 10x pipe diameter down stream). The pool company installed it right next to the h2flowmeter, so my guess is that the 135 gpm reading on the BW flow meter is incorrect as it does not have 15" of straight pipe upstream and may be impacted by turbulence from the h2flowmeter. We'll start by affixing that new label to the h2flowmeter when it arrives and see where we are. If we get the 170 gpm we need, then no need to re-install the BW flow meter. If we are still under the required flow rate, I might have them clean and re-install the BW flow meter temporarily in the return line after the filter to see if we get a different reading there. Will update when we get to that point. Thanks.

I think you misunderstood my point. I was not referring to your current measurements.

The manufactures specifications for error are much higher for the BW (10% of full scale) than the FlowVis (2% of full scale) so even when both are installed properly, you still cannot trust the BW readings. The BW readings can still be quite a bit off from the FlowVis.

 

[JamesW]

Claims of ≥98.1% accuracy seem unlikely to me.

Maybe +/- 5% is more realistic.

B. Straight horizontal pipe of ≥11” before FlowVis is required for this accuracy.

https://static1.squarespace.com/static/6054f4b7f30c7f1e91e1f2e9/t/64234e3bf8631f21bbe21b47/1680035390691/FlowVis-Head+Loss+Data+R1.0.pdf

https://static1.squarespace.com/static/6054f4b7f30c7f1e91e1f2e9/t/645bfb63a1cb967315606938/1683749737544/FlowVis+Manual+Rev6.1.pdf

KEY FEATURES
Installation flexibility; installs horizontally, vertically, or even upside-down

Can be installed with little-to-zero straight pipe requirements with no effect on accuracy

≥98.1% accuracy across the entire model range

Models available for 1.5” - 8” and metric units for DN80 - DN200

More NSF 50 certified models than any other brand of flow meter

Doubles as a check valve (1.5”, 2”, and 2.5” models)

Digital upgrade (model FV-D) available for all FlowVis models

The first and only flow meter for pools and spas to be certified for outdoor use

Clear, easy-to-read scale in GPM or optional LPM or m3/h

Installs quickly and easily with no calibration required

Manufactured in the USA

15-year design life, 3-year warranty

FlowVis flow meter — H2Flow Controls

FlowVis flow meters are a revolution in reliable flow measurement. With unrivaled average accuracy, greater installation flexibility, and more NSF 50 certified models than any other brand, it’s easy to see why FlowVis® is a brand of flow meter you can put your trust in.

www.h2flow.net

 

[JamesW]

In my opinion, 170 GPM is a bit ridiculous for this pool and unnecessary.

167 GPM is required to turnover 60,000 gallons in 6 hours.

However, the code is what it is, so you probably have to meet the requirements.

If you had the Schedule 40 scale and schedule 80 pipe before and after the flowmeter, that would improve the flow reading, but don't do that.

The flow based on head loss and the pump performance curve seems to be significantly off from the flow meter readings.

Maybe the pump is underperforming for some reason?

 

[JamesW]

Claims of ≥98.1% accuracy seem unlikely to me.

Basically, this means that a reading of 170 GPM will indicate that the actual reading is between about 166.243 and 173.757 GPM to 98% certainty.

bell curve mean 170 standard deviation 1.615 - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

 

[JPMorgan]

B. Straight horizontal pipe of ≥11” before FlowVis is required for this accuracy.

We definitely have 11" of straight pipe before the FlowVis.... more like 30". Just have to remove that BW flow meter that was installed in front of it.

 

[JPMorgan]

167 GPM is required to turnover 60,000 gallons in 6 hours.

However, the code is what it is, so you probably have to meet the requirements.

Yes.... I agree. Even at 135 gpm, that is more than 3 turnovers of the entire pool daily. At 155 gpm we are almost turning the pool over 4 times daily (3.7 x by my calculations). State wants 4 x turnover of water daily. It will be interesting to see how rigid the inspector is when we finally get the inspection done... especially since that flow meter is a little tricky to read given the way it was installed.

 

[JPMorgan]

The flow based on head loss and the pump performance curve seems to be significantly off from the flow meter readings.

Maybe the pump is underperforming for some reason?

I guess this is the next thing to consider if the flow rate doesn't improve after the new label is affixed... why is the pump not producing the flow that it should? Will cross that bridge when we get there...

 

[JPMorgan]

I think you misunderstood my point. I was not referring to your current measurements.

The manufactures specifications for error are much higher for the BW (10% of full scale) than the FlowVis (2% of full scale) so even when both are installed properly, you still cannot trust the BW readings. The BW readings can still be quite a bit off from the FlowVis.

I guess what you are saying is that there is really no point in installing the BW flow meter as a check on the flow rate that we are getting from the h2flowmeter because the h2flowmeter is the more accurate device.

 

[JamesW]

Looks like the same issue as we had before?

Filter capacity?

We are currently getting about 100 gpm from our outdoor pool pump. I'm told the pump is capable of much more flow than that. The state regs say our pool should turn over every 6 hours, so that's 167 gpm required for our 60,000 gallon pool. We had the pump checked out and were told the...

www.troublefreepool.com

 

[JPMorgan]

Looks like the same issue as we had before?

Filter capacity?

We are currently getting about 100 gpm from our outdoor pool pump. I'm told the pump is capable of much more flow than that. The state regs say our pool should turn over every 6 hours, so that's 167 gpm required for our 60,000 gallon pool. We had the pump checked out and were told the...

www.troublefreepool.com

Yes.... we were well below the required flow rate when I posted that. We had the pump serviced.... spent about $1,800 to replace the impeller and other internal pump parts. After that work and at the start of this season we were getting readings of 170-180 gpm. Then the new equipment was installed in late May (including the new h2flowmeter that I just figured out is the wrong one) and the flow rate is now reading 135 gpm.

 

[JPMorgan]

Maybe the BW flow meter that was installed on the plumbing previously was giving false readings.... who knows. Just hoping that I see 170 gpm when we put the new sticker on the h2flowmeter and that will be the end of it. If not, more investigation will need to be done.