Figuring Flow Rate

[bottomcat]

Okay, so maybe my pressure is not too low. Are you running 1.5" line or something larger?

[bottomcat]

Maybe I shouldn’t be trying to calculate flow rate but just finding the correct performance curve? Is there anyone out there who can provide the curves for the pump I describe in tis thread? The performance curves given here: http://www.pentairpool.com/pdfs/stariteoptifloDS.pdf only go down to ¾ HP but I need the data for ¼ HP. Even with the curve, what formulas should I use to compute the total head?

Appreciate any help I can get, as I won’t buy the heater until I know if it will work with my system.

[mas985]

Assuming you have the 1 1/2 HP Optiflo pump, flow rate on typical AG plumbing is 50 GPM on high which means it would be about 25 GPM on low speed. So marginal. But a heater's operation is dictated not on flow rate but on pressure. If the pressure is too low, the heater will not kick on but because you have an AG pool, the pressure should be fine on low speed.

If you want more than guess, I would need a picture of your equipment setup and also the filter pressure on high speed.

[GaryT]

Get a 40 - 60gal barrel and backwash into it for 1 minute.
Volume will give you your flow rate

[mas985]

Backwash flow rates can be significantly higher than normal flow rates because backwash mode bypasses most of the return side plumbing so that method will not be very accurate.

[bottomcat]

But a heater's operation is dictated not on flow rate but on pressure.

@mas985: Thanks for replying. The reason I said the heater required a minimum flow is because the Service and Installation Manual specifies minimum flow on page 26 here: https://www.hayward-pool.com/pdf/man...stallation.pdf

If you want more than guess, I would need a picture of your equipment setup and also the filter pressure on high speed.

The pressure on high is 15 psi. I'll send pictures tomorrow.

Thanks!

[nefretrameses]

You can put a flow meter in your system. Try www.bestbuypoolsupply.com. Look under "in ground solar parts" and scroll down to the bottom of the page. About $60.00. Mark may want to comment about their accuracy.

[bottomcat]

'rameses, I considered getting one. I might use Gary's trick, but just disconnect the return line to fill the bucket.

[mas985]

Any modification to the return side plumbing will have a dramatic affect on the flow rate so again, would not be very accurate.

[bottomcat]

If you want more than guess, I would need a picture of your equipment setup and also the filter pressure on high speed.

Mark, here are the pictures (I think… never done this before):