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?

Thanks in advance for any advice

Welcome to TFP!

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

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.

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

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.

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.

Thanks for all the detailed questions to help us with an answer. I'm going to follow up with more info.

Detailed questions that dovetailed from this thread here:

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