Backwash procedure for pool with 2 filters

[JamesW]

With the VS Pump, you could adjust the speed up to the exact required level and not higher.

This will meet the needs without going higher than necessary.

 

[JPMorgan]

Variable speed would allow you to turn it down at times where the full speed is not required.

I believe the state requires 170 gpm constantly. If that is the case does a VS pump make sense?

 

[Lake Placid]

VS would allow you to run at the lowest speed possible to maintain 170 gpm, thus some potential for energy savings. Given the referenced pump has flow control, you could try and use that to maintain the requisite GPM flow as the filters clog etc, it theoretically would increase speed to allow you to stay within regs. Is that really necessary, no. I’ve never seen a health inspector standing over a flow meter waiting to shut you down when the flow rate drops to 169 gpm. Typically they just check the box that you have a flow meter installed and move on with their day, probably not even looking at the flow rate.

 

[mas985]

If the flow meter is correct and the pressure/suction measurements are correct, the current operating point would be
120 GPM @ 81.5 ft of head and a plumbing curve of:

Head (ft) = 0.00566 * GPM ^2

Which crosses the Whisperflo 5 HP head curve close to the same operating point of 120 GPM @ 81.5' of head. So this pump may not be any better.

Of course we are still not certain which measurements are correct and if the current pump is operating as indicated by the head curve.

 

[JamesW]

 

[mas985]

DMH impeller is actually closer to the measurements.

 

[mas985]

Operating point A assumes:
- Pump pressure and suction gauge measurements are correct
- Flow meter measurement is incorrect
- Pump is operating on the DMJ head curve

Operating point B assumes:
- Pump pressure and suction gauge measurements are correct
- Flow meter measurement is correct
- Pump is NOT operating on the DMJ head curve

Operating point C assumes:
- Pump pressure and suction gauge measurements are incorrect
- Flow meter measurements are correct
- Pump is operating on the DMJ head curve

Only one of these is valid

 

[JamesW]

Only one of these is correct

Maybe put a new vacuum gauge on the suction and a new pressure gauge directly after the pump.

 

[JamesW]

Are we 100% sure that the pump is rotating the correct direction?

For 3 phase power, it is easy to get reverse rotation.

Can you show a video of the operation with the rotation being verified?

Can you check the RPM?

Can you check the power being used?

What is the voltage being used?

Check amperage on all three wires.

 

[JamesW]

Only one of these is valid

It could be a combination of all three things being off.

- Pump pressure and suction gauge measurements are incorrect
- Flow meter measurement is incorrect
- Pump is NOT operating on the DMJ head curve.

In my opinion, the Pump NOT operating on the DMJ head curve is the most likely issue.

 

[mas985]

In my opinion, the Pump NOT operating on the DMJ head curve is the most likely issue.

That was my thought as well.

 

[JamesW]

 

[mas985]

A clog in the impeller would steepen the head curve which could explain the measurements:

 

[JamesW]

First.... thanks for all your help with this.... invaluable and greatly appreciated!

Pictures of the impeller that the pool company sent me this morning are attached. I asked them to return the part, so I have evidence for the Board (in case questions arise). The Service Manger told me the impeller and diffuser were "on their last days and I doubt they would have made it much longer"

I'm not sure if the pump ever worked properly. I have been here 2 years and I understand the pump is about 10 years old. The highest flow rate reading I see from past records going back 2-3 years was 100 gpm. Mostly, the flow rate was never recorded! No one ever made an issue of it, including our current pool company (not the same company that replaced the impeller recently). I'm trying not to use our current pool service provider because I think they are incompetent and am trying to replace them. It isn't until recently that I became aware of the minimum flow rate requirement by reading the regulations and doing the calculations myself. The pool company should have known this and addressed it long ago. (They also allowed CYA in the pool to get to 180 ppm before I arrived here and tested the water..... they should have been fired immediately!)

 

[JamesW]

Why was the impeller so torn up?

Maybe a cavitation problem?

 

[mas985]

That looks like it might have experienced some cavitation.

 

[JamesW]

 

[JamesW]

Are the parts brass or bronze or cast iron or what?

 

[JamesW]

 

[JamesW]

Probably need to open the pump and check the condition of the parts.