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Post subject: how do i measure flow rate of water?
Posted: June 26th, 2012, 6:35 pm
 New User

Joined: June 26th, 2012, 5:35 pm
Posts: 1
I have a raypak above ground pool and spa heater I am newly installing, the instructions say I must have an external auxiliary bypass valve if rates exceed 70 gallons per minute. How do I measure flow rate?

Post subject: Re: how do i measure flow rate of water?
Posted: June 26th, 2012, 6:58 pm

Joined: May 7th, 2007, 3:03 pm
Posts: 29847
Location: Silver Spring, MD
Welcome to TFP!

There isn't any easy way. What size pump do you have?

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19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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Post subject: Re: how do i measure flow rate of water?
Posted: June 26th, 2012, 7:46 pm

Joined: April 30th, 2011, 3:17 pm
Posts: 390
Location: Lynchburg VA
Can you hook up a hose to the return fitting so you can fill a 5G bucket. You can see how long it takes to fill the bucket and do the math. I know it's a bit primitive but it will give you an idea.

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Post subject: Re: how do i measure flow rate of water?
Posted: June 26th, 2012, 8:04 pm
 TFP Expert

Joined: May 3rd, 2007, 9:45 am
Posts: 5345
Location: Pleasanton, CA
Putting a standard hose on the return fitting will increase head loss significantly so the flow rate will not be very accurate.

I can estimate the flow rate for you but I need the following information:

Suction pipe diameter (e.g. 1.5", 2", 2.5")
Average length of suction pipes
Number of individual suction pipes from the water to the equipment
Number and type of suction side valves
Current Pump Make/Model
Height of pump relative to the water level
Pipe size between pump and filter (e.g. 1.5", 2", 2.5")
Filter type, size and multi-port valve size
Filter PSI reading at the desired valve settings and pump's highest speed setting
Height of pressure gauge relative to the pump center line
Heater - yes or no
Number and type of return side valves
Return pipe diameter (e.g. 1.5", 2", 2.5")
Average length of return pipes
Number of individual return pipes from the equipment to the water
Return eyeball/jet inner diameter (e.g. 1", 3/4", 1/2") or Jets (e.g. 3/8", 7/16")
Number of return eyeballs
Optional: Pump suction reading (in-hg) - not necessary but improves accuracy

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Mark

Hydraulics 101;Pump Ed 101; Pump and Pool Spreadsheets; FSEC Solar Panel Information
18'x36' 20k gallon plaster/gunite pool, 1/2 FRHP 2 speed pump, Aqualogic PS8 SWCG, 425 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa/1 FRHP jet pump, 400k BTU NG Heater, ThePoolCleaner

Post subject: Re: how do i measure flow rate of water?
Posted: June 26th, 2012, 9:34 pm
 TFP Expert

Joined: January 6th, 2010, 10:54 am
Posts: 6871
Location: San Dimas, CA (LA County)
traciejo@gmail.com wrote:
I have a raypak above ground pool and spa heater I am newly installing, the instructions say I must have an external auxiliary bypass valve if rates exceed 70 gallons per minute. How do I measure flow rate?

Here's how I got a rough idea of my flow. I did mine to calculate how long to turn the water over so I could set my filter timer.

I set the valves to suck from the spa and return to the pool. I stuck a ruler in there and got a depth from the seat, then timed it until it went down 6". Then I shut it down, reversed the valves, and measured how long it took to raise the water level again. I figured going both directions would give me the average since the lines are all different lengths.

My spa is round. I broke out the tape measure and got the diameter, then crunched some numbers and came up with how many gallons I moved and how long it took to do it. Answer is GPM.

In case math isn't your strong point, just post the measurements and someone can crunch the numbers for you.

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Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
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Post subject: Re: how do i measure flow rate of water?
Posted: June 26th, 2012, 10:29 pm
 Special Expert

Joined: March 2nd, 2011, 8:02 pm
Posts: 2345

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Post subject: Re: how do i measure flow rate of water?
Posted: June 27th, 2012, 5:05 pm
 New User

Joined: June 25th, 2012, 7:43 pm
Posts: 3
Location: Springfield, OR
Hello, this is my first post. The 1st poster in this thread, traciejo (my gf) posted while I was out shopping for some parts for the pool we are assembling, I was having her read the heater manual and see if she could help me figure out our install.

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AG 7300 gallons, 18ft Wilbar Industries “Summerfield” (but sold as a “Key West”)
Filter: Millennium 22'' Sand w/ 1.5HP 1 speed 120V
Raypak heater Model 130A (P-R130A-EN-C)

Post subject: Re: how do i measure flow rate of water?
Posted: June 27th, 2012, 8:02 pm
 New User

Joined: June 25th, 2012, 7:43 pm
Posts: 3
Location: Springfield, OR
Detailed questions that dovetailed from this thread here:

many-questions-related-to-our-wilbar-18ft-ag-pool-install-t48479.html

_________________
AG 7300 gallons, 18ft Wilbar Industries “Summerfield” (but sold as a “Key West”)
Filter: Millennium 22'' Sand w/ 1.5HP 1 speed 120V
Raypak heater Model 130A (P-R130A-EN-C)

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