- Jan 4, 2016
- 5,295
- Pool Size
- 44000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
Summary
The FlowVis Flow Meter is a comparatively low cost addition to pool plumbing that provides a cross-check that your system is performing normally. The meter can help with optimizing a heating system. The information provided by the meter can also be estimated other ways. The FlowVis is reliable and will not add a noticeable amount to operating cost, provided it’s installed where you would otherwise have a check valve. The FlowVis can be shared with other pool owners, or on other plumbing circuits by moving it to other Jandy, Praher or Hayward check valves.
Description of the device
The FlowVis Flow Meter (FlowVis) is a device used to measure the flow rate of water in a plumbing system. The 1.5”, 2” and 2.5” models are a modification of a spring loaded check valve, and also serve as a check valve. The FlowVis can be installed anywhere in a plumbing circuit that has the flow you want to measure. Last I checked, the meter costs US$175 for the 2” model (AU$325, 50 mm).
The FlowVis should be installed so that you can look into the gauge, along the red vane. Here’s a video that shows the FlowVis in operation: FlowVis® Flow Meter - H2flow Review Overview - YouTube
The FlowVis can be installed as a stand-alone device, or as a retrofit to a Jandy, Hayward or Praher check valve. The FlowVis is simple, reliable and easy to install. With the circulation system running at a stable pressure, simply observe the gauge to determine flow rate in gallons per minute (or litres per minute in the metric version).
If installed as a stand-alone, head loss will increase by about 2 feet at 40 GPM (150 LPM) in 2" (50mm) pipe, and this is more than the head loss through a conventional spring-loaded flapper check valve. This manual has the head loss data: FlowVis Manual. I noticed a misleading statement on page 10: "NOTE: One 90o elbow equals 5.7 feet", which suggests this statement can be compared to head loss in feet shown for the FlowVis above. I believe the statement should read: "Note: One 90o elbow equals 5.7 feet of pipe" which would be roughly 0.6 feet of head loss at 40 GPM in 2" pipe. Suffice to say that in terms of head loss, the stand-alone FlowVis should be equivalent to three or four 90s (if compared for 2" pipe at 40 GPM).
[Edit 9-Feb-18] Flowvis 2"/2.5" version, 0.77 PSI at 20 GPM and 2.37 PSI at 112.6 GPM (1.8 feet and 5.5 feet respectively)
By comparison, figures from Jandy for a 2" check valve are ~0.7 feet at 20 GPM and ~3.4 feet at ~112 GPM [End Edit]
Accuracy is reported by the manufacturer as ‘greater than 95%’ and ‘>97.9%’. I’m able to realistically read the scale to increments of about 5 litres per minute (approx. 1.3 gallons per minute) with flows ranging from 80 to 220 litres per minute (approx. 20 to 60 gallons per minute). So in practical terms, I can get readings within +/- 6%. To achieve this accuracy, you need to be able to look at the FlowVis with your eye aligned with the upper surface of the gauge vane.
Practical uses
Flow rate can be estimated from a pump curve, by using the filter pressure and applying a factor for the likely flow resistance arising from the suction piping and fittings. Therefore there is no critical need for a flow meter on a residential pool circulation system.
But it’s been handy for me in a few situations.
If the suction side gets restricted, for example by dirty strainer baskets, then flow can be reduced without the filter pressure gauge revealing a problem. In these conditions, the pump’s ability to pull water is lessened. If the filter is clean, a lower than “clean pressure” reading will be seen. However if the filter is dirty, filter pressure may read as normal while the flow is actually significantly reduced. A quick glance at the flow meter reveals this condition. I took a few pictures which might help explain it.
My filter pressure was normal, but I noticed that my flow was low, checked the skimmer, and the thermometer was blocking the opening in the skimmer vacuum plate. Yep, I know. Why not just keep the strainer baskets clean? But that could be said about a lot of things. The extra information drew my attention to the problem and I went and found the thermometer blocking the hole in the skimmer vacuum plate. Once it was removed, my filter pressure went up along with the flow rate.
I’ve learned the flow rate that satisfies my salt water chlorinator. By observing the FlowVis, I could observe the loss of flow as the filter gets dirty, and determine when the filter needs to be cleaned. I let my sand filter get considerably dirtier than the 25% recommendation because I’ve noticed that my water just gets that much cleaner. As I was getting used to this, I could glance at the FlowVis and know that I wasn’t going too far for the salt water chlorinator.
I may yet add a heat pump. Ideal flow for a heat pump is the slowest flow that extracts all the heat that the heat pump is capable of. Same can be said for a natural gas heater. According to a respected expert here at TFP, slower flow preserves the heat exchanger from turbulence wear. I can't speak to this from my own experience, but it's certainly consistent with my other water handling experience. That said, most heaters have internal bypasses which may or may not be user-adjustable. It’s challenging to fine tune a heater bypass and actually know the flow, but it could be done with the FlowVis. Certainly, ensuring the flow rate is within spec can easily be done.
The FlowVis might provide useful information for other things such as water features or negative edges, and would be useful during some trouble-shooting efforts. The meter is informative when messing around with pump speeds on a VS pump.
The next two are geeky and perhaps irrelevant to most.
I wanted to know how many Btu (kWh) I was getting out of my solar heating system, so I could know the value I’m getting from circulating water up onto the roof. The FlowVis gave me the flow rate and I measured the change in temperature, so I was able to make some reasonable estimates of heat gained vs. electricity needed to circulate the water.
I tested my return water for FC and compared this to the pool FC. I was able to calculate the contribution of FC from the salt water chorinator and know that it’s performing the way it should be.
Conclusion
Is it worth it? Only an individual pool owner can decide that one. If you got an extra year of life from a pool heater, there might be a payback, but I can’t see other monetary benefits. [Edit] A TFP member mentioned that taking a reading from a flow meter is a big time-saver compared to measuring the plumbing layout, recording equipment and fittings, and then assessing against charts or calculators, and for many people, time is money [End Edit]. It’s fair to say that I only really needed or wanted the FlowVis for initial measurements, and could certainly set it aside and put the original check valve back on. I leave it on because I enjoy the reassurance of knowing my flow rate(s).
For completeness, I have no financial interest in H2Flow Controls, FlowVis, or any other pool supply business.
The FlowVis Flow Meter is a comparatively low cost addition to pool plumbing that provides a cross-check that your system is performing normally. The meter can help with optimizing a heating system. The information provided by the meter can also be estimated other ways. The FlowVis is reliable and will not add a noticeable amount to operating cost, provided it’s installed where you would otherwise have a check valve. The FlowVis can be shared with other pool owners, or on other plumbing circuits by moving it to other Jandy, Praher or Hayward check valves.
Description of the device
The FlowVis Flow Meter (FlowVis) is a device used to measure the flow rate of water in a plumbing system. The 1.5”, 2” and 2.5” models are a modification of a spring loaded check valve, and also serve as a check valve. The FlowVis can be installed anywhere in a plumbing circuit that has the flow you want to measure. Last I checked, the meter costs US$175 for the 2” model (AU$325, 50 mm).
The FlowVis should be installed so that you can look into the gauge, along the red vane. Here’s a video that shows the FlowVis in operation: FlowVis® Flow Meter - H2flow Review Overview - YouTube
The FlowVis can be installed as a stand-alone device, or as a retrofit to a Jandy, Hayward or Praher check valve. The FlowVis is simple, reliable and easy to install. With the circulation system running at a stable pressure, simply observe the gauge to determine flow rate in gallons per minute (or litres per minute in the metric version).
If installed as a stand-alone, head loss will increase by about 2 feet at 40 GPM (150 LPM) in 2" (50mm) pipe, and this is more than the head loss through a conventional spring-loaded flapper check valve. This manual has the head loss data: FlowVis Manual. I noticed a misleading statement on page 10: "NOTE: One 90o elbow equals 5.7 feet", which suggests this statement can be compared to head loss in feet shown for the FlowVis above. I believe the statement should read: "Note: One 90o elbow equals 5.7 feet of pipe" which would be roughly 0.6 feet of head loss at 40 GPM in 2" pipe. Suffice to say that in terms of head loss, the stand-alone FlowVis should be equivalent to three or four 90s (if compared for 2" pipe at 40 GPM).
[Edit 9-Feb-18] Flowvis 2"/2.5" version, 0.77 PSI at 20 GPM and 2.37 PSI at 112.6 GPM (1.8 feet and 5.5 feet respectively)
By comparison, figures from Jandy for a 2" check valve are ~0.7 feet at 20 GPM and ~3.4 feet at ~112 GPM [End Edit]
Accuracy is reported by the manufacturer as ‘greater than 95%’ and ‘>97.9%’. I’m able to realistically read the scale to increments of about 5 litres per minute (approx. 1.3 gallons per minute) with flows ranging from 80 to 220 litres per minute (approx. 20 to 60 gallons per minute). So in practical terms, I can get readings within +/- 6%. To achieve this accuracy, you need to be able to look at the FlowVis with your eye aligned with the upper surface of the gauge vane.
Practical uses
Flow rate can be estimated from a pump curve, by using the filter pressure and applying a factor for the likely flow resistance arising from the suction piping and fittings. Therefore there is no critical need for a flow meter on a residential pool circulation system.
But it’s been handy for me in a few situations.
If the suction side gets restricted, for example by dirty strainer baskets, then flow can be reduced without the filter pressure gauge revealing a problem. In these conditions, the pump’s ability to pull water is lessened. If the filter is clean, a lower than “clean pressure” reading will be seen. However if the filter is dirty, filter pressure may read as normal while the flow is actually significantly reduced. A quick glance at the flow meter reveals this condition. I took a few pictures which might help explain it.
My filter pressure was normal, but I noticed that my flow was low, checked the skimmer, and the thermometer was blocking the opening in the skimmer vacuum plate. Yep, I know. Why not just keep the strainer baskets clean? But that could be said about a lot of things. The extra information drew my attention to the problem and I went and found the thermometer blocking the hole in the skimmer vacuum plate. Once it was removed, my filter pressure went up along with the flow rate.
I’ve learned the flow rate that satisfies my salt water chlorinator. By observing the FlowVis, I could observe the loss of flow as the filter gets dirty, and determine when the filter needs to be cleaned. I let my sand filter get considerably dirtier than the 25% recommendation because I’ve noticed that my water just gets that much cleaner. As I was getting used to this, I could glance at the FlowVis and know that I wasn’t going too far for the salt water chlorinator.
I may yet add a heat pump. Ideal flow for a heat pump is the slowest flow that extracts all the heat that the heat pump is capable of. Same can be said for a natural gas heater. According to a respected expert here at TFP, slower flow preserves the heat exchanger from turbulence wear. I can't speak to this from my own experience, but it's certainly consistent with my other water handling experience. That said, most heaters have internal bypasses which may or may not be user-adjustable. It’s challenging to fine tune a heater bypass and actually know the flow, but it could be done with the FlowVis. Certainly, ensuring the flow rate is within spec can easily be done.
The FlowVis might provide useful information for other things such as water features or negative edges, and would be useful during some trouble-shooting efforts. The meter is informative when messing around with pump speeds on a VS pump.
The next two are geeky and perhaps irrelevant to most.
I wanted to know how many Btu (kWh) I was getting out of my solar heating system, so I could know the value I’m getting from circulating water up onto the roof. The FlowVis gave me the flow rate and I measured the change in temperature, so I was able to make some reasonable estimates of heat gained vs. electricity needed to circulate the water.
I tested my return water for FC and compared this to the pool FC. I was able to calculate the contribution of FC from the salt water chorinator and know that it’s performing the way it should be.
Conclusion
Is it worth it? Only an individual pool owner can decide that one. If you got an extra year of life from a pool heater, there might be a payback, but I can’t see other monetary benefits. [Edit] A TFP member mentioned that taking a reading from a flow meter is a big time-saver compared to measuring the plumbing layout, recording equipment and fittings, and then assessing against charts or calculators, and for many people, time is money [End Edit]. It’s fair to say that I only really needed or wanted the FlowVis for initial measurements, and could certainly set it aside and put the original check valve back on. I leave it on because I enjoy the reassurance of knowing my flow rate(s).
For completeness, I have no financial interest in H2Flow Controls, FlowVis, or any other pool supply business.
