New 4x160 pump question

[newfool]

Hello all, I have a 4x160 pump and wanted to know if this was a good way to go about finding flow rate.

I used my pump to draw water from the pool and used the drain valve with hose to fill up a 5 gallon bucket. I checked to see how long it would take on the first 3 speeds. The thing i was wondering about was how can I compare a 2" flexible vinyl hose running say 20' versus my 2" sch 40 inground run going back to the pool (returns). Or is this method accurate enough to give me a way of determining runtime to cycle my water at least 1 turn daily.

Thanks for any input!

 

[JasonLion]

There is no easy way to measure flow rate accurately unless you get a flow meter. Blue and White makes some flow meters that work well for under $100. Any kind of hose you attach is going to change the flow rate.

Most of the time there is no real need to know the flow rate. You can usually adjust things based on how the water looks after a week of operation, though doing that sometimes gets tedious.

 

[mas985]

As Jason pointed out, the most accurate method is with a flow meter. If you don't want to go that route, you can use the filter pressure and a vacuum measurement at the pump basket to determine total head and then look up the flow rate on the head curves. This is a little challenging for the Intelliflo since they don't show all of the RPM values but you can use this fitted curve approximation to determine the flow rate from head loss:

GPM = 218 * sqrt ((RPM / 3450) ^ 2 - (Total Head loss / 96))

If you don't want to get a vacuum guage, you can use and even rougher approximation of:

Total Head = 3.5 * Filter PSI (assumes suction head is 50% of return head)

That should get you pretty close.

 

[launboy]

The way I did it was to hold a short (2 foot)piece of flexible hose against my return and let it flow into a 5 gal. bucket sitting next to the pool. I ended up wath 30 GPM which seems low for a 1HP pump although it was filtering and pushing the water 12 feet up to the roof for the solar. It also has to suck the water 30' to and from the pool.(2 inch PVC)

Adam

 

[newfool]

Awesome info guys, thanks for the 411. I will look into the math aspect as I believe I have a vac. gauge that I can try.