Filter capacity?

[JPMorgan]

We are currently getting about 100 gpm from our outdoor pool pump. I'm told the pump is capable of much more flow than that. The state regs say our pool should turn over every 6 hours, so that's 167 gpm required for our 60,000 gallon pool. We had the pump checked out and were told the impeller is worn and needs to be replaced.... recommended new impeller, diffuser, and shaft seal. Make sense?

Is there any reason why the flow rate on the pump might be throttled back via some valves in the plumbing system, i.e. to match what the filters can handle? We have 2 Pentair TR-140 sand filters on the system. After backwashing, PSI on filters is usually around 22.

 

[JamesW]

Pictures of the system, pump, pump labels and motor labels?

 

[JamesW]

We had the pump checked out and were told the impeller is worn and needs to be replaced.... recommended new impeller, diffuser, and shaft seal. Make sense?

Show the impeller.

Did they provide pictures of the impeller to prove that it is worn?

Is the impeller plastic or metal?

What is the make and model of the pump?

Did they take the pump apart to inspect the impeller or are they just guessing about the impeller being worn?

 

[ajw22]

If the flow is split in parallel between the TR140s then the filter should not be your limitation…

 

[JamesW]

The TR-140 is rated at 106 GPM (7.06 x 15 gpm/sqft).

2 = 212 GPM.

At 106 GPM, the head loss is about 12 feet from the filter, which is about 5.2 psi.

At 106 GPM, the head loss from the multiport is about 6 psi.

That is 11.2 psi from the filter and valve at 212 GPM total system flow.

https://www.pentair.com/content/dam/extranet/nam/pentair-pool/commercial/manuals/filters/triton-instructions-english-spanish-french.pdf

https://images.inyopools.com/cloud/documents/PRAHER-MPV-OWNERS-MANUAL-MPV031017-REV-2.pdf

https://www.pentair.com/content/dam/extranet/nam/pentair-pool/residential/manuals/valves/hiflow-side-mounted-backwash-valve-manual-english.pdf

 

[JamesW]

SS Pump (SIR "D" Series #DMJ3H177)

Is it this: DMJ3-111

https://images.inyopools.com/cloud/documents/starite-d-series-pump.pdf

 

[Bperry]

The TR-140 is rated at 106 GPM (7.06 x 15 gpm/sqft).

2 = 212 GPM.

Finally some math from James that I can follow along with.

 

[JamesW]

22 psi is about 51 feet of head.

You also have the suction head loss, which can be estimated to be about 9 feet of head for a total of 60 feet of head.

That should provide about 200 gpm.

Maybe the suction is clogged?

Do you have a suction pressure reading from a vacuum gauge?

If not, you should get one.

After backwashing, PSI on filters is usually around 22.

 

[JamesW]

100 GPM on a DMJ is way too low and implies a total system head loss of about 129 feet.

The impeller is bronze and it might be damaged.

Sometimes a metal impeller will get corroded or damaged by chemicals or maybe cavitation.

Are you sure that your flow meter is working correctly?

https://www.pentair.com/content/dam/extranet/web/nam/sta-rite/data-sheets/s4517ws.pdf

Pentair Sta-Rite D Series Medium Head Centrifugal Pumps

Available in high head or medium head series (high-head in separate listing). Feature leak-proof mechanical seals, easy service design, heavy-duty motors, rugged construction.

www.pentair.com

 

[JPMorgan]

Pictures of the system, pump, pump labels and motor labels?

I will post pics tomorrow.

 

[JPMorgan]

Show the impeller.

Did they provide pictures of the impeller to prove that it is worn?

Is the impeller plastic or metal?

What is the make and model of the pump?

Did they take the pump apart to inspect the impeller or are they just guessing about the impeller being worn?

The technician was having trouble accessing the impeller due to frozen bolts and didn't want to force the issue and cause our pool to be out of service for the holiday weekend, so he snapped these pictures from inside the pump pot. I believe it is a metal impeller. Pump is SIR "D" Series #DMJ3H177

 

[JPMorgan]

SS Pump (SIR "D" Series #DMJ3H177)

Is it this: DMJ3-111

View attachment 527249

https://images.inyopools.com/cloud/documents/starite-d-series-pump.pdf

I will check the model number on the pump and post in the morning

 

[JPMorgan]

Maybe the suction is clogged?

Do you have a suction pressure reading from a vacuum gauge?

If not, you should get one.

I will check and post in the morning.

 

[JPMorgan]

100 GPM on a DMJ is way too low and implies a total system head loss of about 129 feet.

The impeller is bronze and it might be damaged.

Sometimes a metal impeller will get corroded or damaged by chemicals or maybe cavitation.

Are you sure that your flow meter is working correctly?

Agree...all signs are leading to a damaged impeller. Yes.... pretty sure the flow meter is working correctly. It is installed in the plumbing after the pump, but before the filter. Is that the correct location for the flow meter? It looks like another one was installed in the return line (after the filter), but that one is inoperable.

 

[JPMorgan]

Here are pics of the two flow meters. The one with the red float in it has a valve at the top to allow it to be flushed and the float moves freely in the tube when that valve is opened. The other flow meter seems to be out of commission.

 

[JamesW]

SIR "D" Series #DMJ3H177

I don't think that that is a valid pump model number.

How old is the pump?

How much is the repair?

You might be better getting a 5 hp commercial Whisperflo VS pump.

That way you can adjust the speed to whatever is required.

Most of the time, you don't need 200 gpm.

 

[JamesW]

The flow meter should be after the filter so that small debris does not get in the meter.

I would question the accuracy of the flow meter.

The cast iron from the pump looks rusted and the repair is likely to not go well.

You probably don't need a 5 hp pump running 24/7 on this pool.

That's probably 5,000 watts.

At $0.20 per kwh, that is $1.00 per hour, $24.00 per day and $720.00 per month.

You can probably cut the cost in half and still maintain the same, or better, water quality.

 

[JamesW]

You might have a suction side air leak at the pump strainer lid.

That can possibly be the reason for the low flow.

Even a small air leak can cause a significant loss of flow.

The metal should be clean and smooth and the O-ring needs to be in good condition and lubricated.

The impeller might or might not be worn, but it seems like more of a guess than anything.

I would start with the strainer lid seal and making sure that the flow meter is functioning properly.

 

[Bperry]

The technician was having trouble accessing the impeller due to frozen bolts and didn't want to force the issue and cause our pool to be out of service for the holiday weekend, so he snapped these pictures from inside the pump pot. I believe it is a metal impeller. Pump is SIR "D" Series #DMJ3H177

The picture just show a bolt with a nut that has surface rust on it. Nothing about the impeller fins that would affect its operation.

 

[JPMorgan]

I don't think that that is a valid pump model number.

How old is the pump?

How much is the repair?

You might be better getting a 5 hp commercial Whisperflo VS pump.

That way you can adjust the speed to whatever is required.

Most of the time, you don't need 200 gpm.

Checked the tags on the pump and motor today along with suction pressure reading on the vacuum guage (see pics). Pump model is DMJ3-172. Pool company quoted repair at $1,800. The engineer we are working with on pool modifications thinks it makes sense to do the repair. Pump is about 10 years old.
If we went with VS pump like the one mentioned, then we would be able to set flow rate at exactly what is required.... is that correct? How much for a new pump like that.. installed? If we do the repair what should we expect in terms of future life of the pump?

Updated Signature with correct pump model.