H2Flow Meter

[JPMorgan]

We recently had some new equipment installed on our outdoor pool. After the equipment was installed the flow rate dropped from 170 gpm to 135 gpm. The pump is the same and only minor plumbing changes were made (from what I can tell). The installation primarily involved a new liquid chlorine feeder and an acid feeder and a new Controller. Everything has been working well, except we are not hitting the required flow rate per regulations since this work was done (which is around 167 gpm).

The FlowVis flow meter that was installed says SCH 80 PIPE on it. However, it is installed on SCH 40 pipe. I looked up the FlowVis flow meter on the company's website and it shows these models for 3" pipe:
FV-3: FlowVis model with GPM scale for 3” pipe. Includes velocity scale and NSF 50 certification.
FV-3-40: FlowVis model with GPM scale for 3” - SCH40 pipe. Includes velocity scale and NSF 50 certification.

Could the flow meter that was installed (stamped SCH 80) be the problem here? Could it be reading the wrong flow rate for the SCH 40 pipe? Could it be that far off, i.e., around 35 gpm? The flow meter is new equipment and was included in the state-required engineering drawings.

 

[PoolStored]

Schedule 40 and 80 pipes have the same OD. Sch 80 has a smaller inside diameter, as the thickness of the pipe is larger.

The schedule 80 flow meter likely has a smaller inside diameter to match the pipe. Sch 80 smaller inside diameter can cause a reduction in flow rate IN GENERAL, and the meter is setup to measure the flow in that type of pipe.

Could it be 35gpm? I don't know, call h2oFlow. 888.635.0296

I'd have whomever did the work, come back and replace the meters with the correct meters.

@mas985

 

[mas985]

We recently had some new equipment installed on our outdoor pool. After the equipment was installed the flow rate dropped from 170 gpm to 135 gpm. The pump is the same and only minor plumbing changes were made (from what I can tell). The installation primarily involved a new liquid chlorine feeder and an acid feeder and a new Controller.

What other equipment was installed? Can you post some pictures of the equipment pad.

Everything has been working well, except we are not hitting the required flow rate per regulations since this work was done (which is around 167 gpm).

I am assuming this is for the Condo pools? You should select "In the Industry" in your profile settings.

The FlowVis flow meter that was installed says SCH 80 PIPE on it. However, it is installed on SCH 40 pipe. I looked up the FlowVis flow meter on the company's website and it shows these models for 3" pipe:
FV-3: FlowVis model with GPM scale for 3” pipe. Includes velocity scale and NSF 50 certification.
FV-3-40: FlowVis model with GPM scale for 3” - SCH40 pipe. Includes velocity scale and NSF 50 certification.

Could the flow meter that was installed (stamped SCH 80) be the problem here? Could it be reading the wrong flow rate for the SCH 40 pipe? Could it be that far off, i.e., around 35 gpm? The flow meter is new equipment and was included in the state-required engineering drawings.

This is from the manual:

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

 

[Lake Placid]

Could the flow meter that was installed (stamped SCH 80) be the problem here? Could it be reading the wrong flow rate for the SCH 40 pipe? Could it be that far off, i.e., around 35 gpm? The flow meter is new equipment and was included in the state-required engineering drawings.

Yes to question 1. Yes to question 2. Yes to question 3 if not installed to design specifications. And yes it’s required for regulation compliance, but that doesn’t mean the inspector has the knowledge or capacity to comprehend that the equipment if not installed as designed will return bad data. If it passed, the inspector was just checking a box. See post #3 by @mas985. Did the plans called out a specific flow meter by model number, or that a flow meter needed to be installed? The installer has verify the flow meter works correctly within the design of the system.

 

[JPMorgan]

What other equipment was installed? Can you post some pictures of the equipment pad.

An Intellichem Controller, a liquid chlorine feeder and an acid feeder.... that's it. I'll take some photos of the pad and post them

I am assuming this is for the Condo pools? You should select "In the Industry" in your profile settings.

Yes, but I don't consider myself "In the Industry". I am not a CPO.... just a fairly knowledgeable volunteer.

Thanks for the info from the FlowVis manual.... that helps!

 

[JPMorgan]

If it passed, the inspector was just checking a box. See post #3 by @mas985. Did the plans called out a specific flow meter by model number, or that a flow meter needed to be installed? The installer has verify the flow meter works correctly within the design of the system.

The installation was done in late May and it has not yet been inspected because of the flow rate issue (which we think will be problematic until it is corrected). The plans state only "install new h2flowmeter between pump and filter."

 

[Lake Placid]

The installation was done in late May and it has not yet been inspected because of the flow rate issue (which we think will be problematic until it is corrected). The plans state only "install new h2flowmeter between pump and filter."

Install a flow meter designed for your application. Follow the design specs for the specific pipe (sch 40/80) and the necessary dimensions of pipe length before and after the meter. Nothing you have installed….

An Intellichem Controller, a liquid chlorine feeder and an acid feeder.... that's it. I'll take some photos of the pad and post them

would have an effect on the required flow.

There is also the possibility that your pump wasn’t and hasn’t been providing sufficient flow required by the regs due to a degraded impeller or other design flaws……and it went unnoticed by the regulatory bodies that inspect the pool.

Case in point….I’m aware of a pool that is theoretically required to turnover the full volume of pool water a minimum every 8 hours, however, based on the botched design/installation of plumbing on the suction side of the pump……and confirmed by the flow meter readings on the effluent side it theoretically turns the full volume every 13 hours. It would never flow enough water to meet the required turn time, in theory…..The crack inspection team has never called out the issue that I’ve heard of, nor cared to do the math to figure out if the theoretical required turnover time is met.

Your call on what you should do if anything to remediate the issue.

 

[JPMorgan]

There is also the possibility that your pump wasn’t and hasn’t been providing sufficient flow required by the regs due to a degraded impeller or other design flaws……and it went unnoticed by the regulatory bodies that inspect the pool.

We were well shy of the required flow rate last year and had the impeller (and other parts) on the pump replaced. After that we were getting the required flow rate. When the equipment was started up this year we were at 170 gpm. After the new equipment was installed the flow meter is reading 135 gpm. The requirement in Illinois is a complete turnover of the pool every 6 hours, so... 60,000 gallons / 360 minutes = 166.7 gpm

Update:
I sent an email to the company that makes the FlowVis flow meter yesterday and got the following response this morning:
"Can you provide the model you are using? I’m guessing FV-3. If that is the case, the scale label w/ be inaccurate. We can provide a sch. 40 scale label to bring the accuracy to 98+%."

I will confirm the flow meter model number today. So.... possibly a simple fix with a new label applied to the flow meter??? In my reply I did also inquire about the need for 3-6" of Sch 80 pipe installed before and after the flow meter as stated in the Manual. We'll see what they say.

Thanks!

 

[JamesW]

Everything has been working well, except we are not hitting the required flow rate per regulations since this work was done (which is around 167 gpm).

The FlowVis flow meter that was installed says SCH 80 PIPE on it. However, it is installed on SCH 40 pipe.

The flow meter works on velocity.

3.042” schedule 40 ID.

2.864” schedule 80 ID.

To get 167 GPM in 3" schedule 80 pipe, the velocity is 8.32 ft/sec.

To get 8.32 ft/sec in 3" schedule 40 pipe, the flow needs to be 189 gpm.

So, that is a 22 gpm error.

If the reading would be 167 GPM with schedule 80 PVC Pipe, the reading with schedule 40 PVC pipe would be 148 GPM, which is an error of 19 GPM or 88.7% of full reading.

Hazen-Williams Water Flow Formula: Head Loss, Data, Charts & Calculator

Friction head loss (<i>ft_H2O per 100 ft pipe</i>) in water pipes can be estimated with the empirical Hazen-Williams equation.

www.engineeringtoolbox.com

 

[JamesW]

The plans state only "install new h2flowmeter between pump and filter."

The flowmeter needs to be After the filter to avoid debris clogging the meter.

When the equipment was started up this year we were at 170 gpm. After the new equipment was installed the flow meter is reading 135 gpm. The requirement in Illinois is a complete turnover of the pool every 6 hours, so... 60,000 gallons / 360 minutes = 166.7 gpm

In my reply I did also inquire about the need for 3-6" of Sch 80 pipe installed before and after the flow meter as stated in the Manual.

A reading of 135 GPM corresponds to a velocity of 6.73 ft/sec in sch 80 PVC Pipe.

For sch 40 pipe, this is 152.3 GPM.

If you used schedule 80 PVC pipe before and after the flow meter, the flow rate reading would change from 135 GPM to about 152 GPM.

This indicates an error of about 17.3 GPM or about 88.6% of full reading.


_____________________________________________________________________________________

 

[JamesW]

The difference in velocity depends on the internal cross-sectional area of the pipe.

Schedule 40 PVC pipe has an Internal Cross-Sectional Area of 7.26789 square inches.

Schedule 80 PVC pipe has an Internal Cross-Sectional Area of 6.44223 square inches.

7.26789 square inches/6.44223 square inches = 1.128.

6.44223/7.26789 = 0.8864.

135 x 1.128 = 152.28.

So, even with the correct pipe size, the flow reading will probably only be 152 GPM, which is below the required flow rate.

What exact pump model do you have?

Can you post the pump performance curve?

What are the suction and discharge pressures?

If the pump is variable speed, what speed are you running?

For flow rate monitoring on a commercial pool, I would prefer to have at least two independent ways of measuring the flow rate.

Maybe get a second flow meter to compare.

 

[JPMorgan]

I will confirm the flow meter model number today. So.... possibly a simple fix with a new label applied to the flow meter??? In my reply I did also inquire about the need for 3-6" of Sch 80 pipe installed before and after the flow meter as stated in the Manual. We'll see what they say.

The company informed me that with the new label they are sending there is no need to install 3-6" of Sch 80 pipe before or after the flow meter. The new label to be affixed to the existing flow meter will give a different reading that will be accurate for Sch 40 pipe. Based on JamesW's comments above it seems doubtful that we are going to see a 35 gpm difference, though. We'll see.

 

[JPMorgan]

Here are photos of the FV-3 flow meter installed on our system. As noted above, the flow meter is for Sch 80 pipe, but it is installed on Sch 40 pipe. The flow meter company says they have a label we can affix to the FV-3 that will provide an accurate reading for the Sch 40 pipe which they are sending to us. it gives us the 167 gpm flow we are looking for.

The second flow meter which sits in front for the FV-3 was installed by the pool company in an attempt to check the flow rate reading on the FV-3, but they are giving roughly the same flow rate. (These are not that easy to read... especially the way the FV-3 was installed.)

 

[JPMorgan]

What exact pump model do you have?

STA-RITE #DMJ3-172

Can you post the pump performance curve?

Where do I find this?

What are the suction and discharge pressures?

I will check these and post

If the pump is variable speed, what speed are you running?

Pump is single speed

I have attached some pics of our set up and the current reading on the extra flow meter... right around 135 gpm

 

[mas985]

Pipe flow is non uniform over the area of pipe. At these velocities, velocity will generally go from 0 near the wall to ~1.2 x Uave at the center line.

Using the power law velocity approximations & assuming the actual flow rate is 170 GPM, the velocity distribution in each schedule of pipe would be similar to this plot:


http://www.eng.famu.fsu.edu/~shih/eml3016/lecture-notes/pipe flow considerations.ppt

The size of the measurement paddle as well as where it sits in the velocity stream comes into play as well as the transition between schedule 40 & 80 will likely introduce additional velocity gradients making the problem even more complex.

Actually, the movement of the check valve is dependent on velocity squared and not just velocity because it is the fluid momentum (i.e. kinetic energy) that moves the paddle. So if we assume the paddle is 2" wide and intersects half the flow, the ratio of KE hitting the paddle is around 1.25x which is very close to the actual ratio of flow rate.

Changing the scale is the easiest thing to try first.

 

[JPMorgan]

Pipe flow is non uniform over the area of pipe. At these velocities, velocity will generally go from 0 near the wall to ~1.2 x Uave at the center line.

Using the power law velocity approximations & assuming the actual flow rate is 170 GPM, the velocity distribution in each schedule of pipe would be similar to this plot:

View attachment 607000
http://www.eng.famu.fsu.edu/~shih/eml3016/lecture-notes/pipe flow considerations.ppt

The size of the measurement paddle as well as where it sits in the velocity stream comes into play as well as the transition between schedule 40 & 80 will likely introduce additional velocity gradients making the problem even more complex. So while the ratio of "average" velocities is around 1.1, the measurement ratio could possibly be more than that although I would not expect to be that much more.

Changing the scale is the easiest thing to try first.

Complicated stuff!!!
Yes.... I agree that affixing the new scale is the first thing to do. Hopefully, that will do the trick. If we were hitting 170 gpm before the install, hopefully we will get that flow rate again. If not, it sounds like a new pump may be the only solution ... unless anyone sees anything in our set up that could be restricting flow. We did recently have our regular pool company (not the one that installed the new equipment) replace some 2" pipe with 3" pipe on the discharge line. They thought that might be restricting the flow, but it didn't make much difference at all.

 

[mas985]

I modified my post above to include this part:

Actually, the movement of the check valve is dependent on velocity squared and not just velocity because it is the fluid momentum (i.e. kinetic energy) that moves the paddle. So if we assume the paddle is 2" wide and intersects half the flow, the ratio of KE hitting the paddle is around 1.25x which is very close to the actual ratio of flow rate.

 

[JamesW]

The Blue/White Flow Meter indicates about 135 GPM on the Schedule 40 scale.

However, this is highly susceptible to debris interfering with accurate operation.

The Blue/White Flow Meter has a tube that should be in the center of the pipe.

 

[JPMorgan]

Here are photos of the pump label and of the suction and discharge pressures for the filters.

 

[mas985]

The BW is also installed right in front of the check valve which you are not supposed to do: