Pump flow

[Xrunner123]

Hi,
I have a hayward SP3007EEAZ pump which spring a leak in one of the seal so I got the rebuild kit and all is good I think.
The pump is old and I think I suffer from low flow issues so I bought a flow meter and measure vac and filter psi and converted it to head pressure.
The equation I'm using from research is Vac*1.3 + pressure*2.31= head.
Is this correct?

Vac measure 5.5inHg and pressure measured 10psi. Flow is 40gpm measured coming out of the filter.
Using the formula this gives 30 feet of head. I have 1.5” suction lines x2 and 1.5” return lines x2.

So if I look at the flow vs head pressure I should be at almost 90gpm but I’m measuring 40. Flowmeter is new.
What am I missing? Do pumps flow less over time? Is equation wrong?

Pool is about 35,000 gallons with FNS36 DE filter and heater.
Thanks

 

[Texas Splash]

Welcome to TFP! Your calculations are more inline with something @mas985 might be able to interpret. Stand by ......

 

[mas985]

Hi,
I have a hayward SP3007EEAZ pump which spring a leak in one of the seal so I got the rebuild kit and all is good I think.
The pump is old and I think I suffer from low flow issues so I bought a flow meter and measure vac and filter psi and converted it to head pressure.
The equation I'm using from research is Vac*1.3 + pressure*2.31= head.
Is this correct?

The correct equation is Vac*1.13 + PSI * 2.31 + Head Offset
Head offset is dependent on where the vacuum and PSI are measured. Were both measured on the pump drain plugs? If so, then there is no head offset.

Vac measure 5.5inHg and pressure measured 10psi. Flow is 40gpm measured coming out of the filter.
Using the formula this gives 30 feet of head. I have 1.5” suction lines x2 and 1.5” return lines x2.

So if I look at the flow vs head pressure I should be at almost 90gpm but I’m measuring 40. Flowmeter is new.
What am I missing? Do pumps flow less over time? Is equation wrong?

Again, it depends on where you measured both parameters.

I am questioning that head curve you posted as well. This is from the manufacture:

Hayward Super 2 Performance Data

	Pump Output (GPM) vs. Total Resistance To Flow (Feet of Head)
Model No. Max Rated	Model No. Full Rated	40 ft	50 ft	60 ft	70 ft	80 ft	90 ft
SP3005X7AZ		47	38	26	12	-	-
SP3007X10AZ	SP3007EECA	63	55	46	32	-	-
SP3010X15AZ	SP3010EEAZ	89	80	69	56	34	-
SP3015X20AZ	SP3015EEAZ	112	102	90	75	56	-
SP3020X25AZ	SP3020EEAZ	132	118	103	86	62	-
SP3025X30AZ	SP3025EEAZ	157	146	133	118	102	80
	SP303063AZ	157	146	133	118	102	80

Which does not match the head curve you are showing.

I also have Energy Star data measurements which more closely matches the table and not the head curve you are showing so I don't think that is the correct head curve.

If you measured on the drain plugs, I get 72 GPM @ 29' of head which still does not match the flow meter.

However, flow meters can be notoriously inaccurate.

What type of flow meter do you have and where is it installed (post pics)?

Also, you need to make sure the gauges are operating correctly. How old are they? Do they read zero when disconnected?

 

[Xrunner123]

Thanks.
The curve came from an owners manual i had but I found a later revison of the the manual on haywards site and the curves are not shown. So I agree maybe they are not correct.

I'm also now doubting the pressure gauge as I went out to check the zero reading which it is but when running and I put slight pressure on the gauge the needle changes. Maybe normal but I bought another one which is on the way.

The flow meter is an Blue-White Residential Pool Flow Meter for 1.50" Pipe.

Thanks again

 

[mas985]

Blue white error can be as much as 10 % full scale so are not very accurate especially if not plumbed in a very long straight pipe. It can't be anywhere near any other fitting. Did you follow their recommendations for placement?

 

[Xrunner123]

Blue white error can be as much as 10 % full scale so are not very accurate especially if not plumbed in a very long straight pipe. It can't be anywhere near any other fitting. Did you follow their recommendations for placement

Here is a picture. Maybe flow meter is too close to backflow preventer.

 

[mas985]

I would say that placement is going to be an issue.

 

[mas985]

Form my experience, I would skip the flow meter and just use pump PSI and vacuum. It is more accurate.

But why do you even care about flow rate?

 

[Xrunner123]

It wound up being a bad pressure gauge. All the numbers make sense now.

I cared about flow rate because the skimmer seemed like it wasn't getting enough flow as i had alot of surface debirs not being skimmed. I was thinking that the pump was not flowing as it should so I wanted to verify this and possibly upgrade to a higher hp motor.
I adjusted the suction valves slightly to fix the skimming issue.
Thanks for your help

 

[mas985]

As long as water travels over the top of the weir door, the skimmer should skim fine. It just may take longer at lower RPM to clean up the surface.