Pump Efficiency, Head, Flow, and related technical info

[msm859]

Can someone give me the short answer? Would it be more efficient(least costly to run) with the Intelliflo to have the slowest GPM to turn over 1x per day AND have the largest pipe with minimum 90's to have the lowest pressure/head???

I am having a pool built and using the Intelliflo and my builder thinks I am too concerned with the over use of 90's and pipe size. He indicates in the past--with the regular Whisperflo he has to use eyeballs to get the head up.

[mas985]

Low head loss in plumbing is a good thing up to a point. As head drops, flow rates increase but so does the power draw of the pump. The peak efficiency of a pump (GPM/Watt) is generally near the middle of the pump head curve.

Another consideration is if you have too little head on the return but too much head on the suction side, you run the risk of sucking in air or worse, pump cavitation.

The only down side of the opposite case (too much return head) is that it reduces the potential flow. So it is best to error on this side which is why most pool plumbing has larger suction pipes than return pipes.

So you really need to match your plumbing system with the pump. To do it properly requires a bit of work which is why most pool builders simply do what they have done before.

If you look at the curves for Richard's pool and the Intelliflow, with the solar off is about as low a head I would go on that pump and with solar on is about as high as I would go so I think it would be well suited for his pool.

Usually 1 - 2 1/2" suction line and 1 - 2" return line is sufficient for most pools. If you have mutliple suction lines from pool to pad I would go with 2" lines and if you have more than 2 return lines, I would go with 1 1/2" return lines.

2 - 2" lines is about the same head loss as 1 - 2 1/2" line.
2 - 1 1/2" lines are about same head loss as 1 - 2" line.

Having said all that, it is much easier to add head to a plumbing system then it is to reduce it as your PB pointed out. So I would always error on the side of large pipes and use ball valves at the pad to control and balance the head for the suction and return. This way you can adjust the plumbing system to get the most GPMs/Watt no matter what pump is put on. Plus, it is difficult to predict exactly how much head a plumbing system will have and is best to measure it after the fact.

Also, post the details of your pool and equipement so we can comment further on the design.

BTW 2 x 45 degree bends are only slightly better than 1 x 90 degree.

[msm859]

Thanks for the explanation. It is an 18 x 36 pool with separate built in spa 6 jets, both have 400 sq" cartridge filters, 2 - intelliflo pumps, single 400 btu mastertemp heater, water feature with Pentair waterfall pump, still debating final finish.

[mas985]

You did not mention your plumbing. What does the pool builder want to put in and what do you want? Lines sizes, number lines, returns, skimmers, main drains, etc. Also, how far from pool to pad.

Your pool size is pretty close to mine and I have two skimmers, a split main drain and 4 returns.

Ideally, I would have each skimmer and the main drain pair on a separate 2" lines all the way back to the pad. 3, 2" lines are equilvalent to a single 3" line plus it will allow you to turn on just one of the three to isolate a suction line for repair or to drain the pool via the main drain only.

For the returns, you could go with one 2.5" line, two 2" lines or four 1.5" lines. Each configuration is equilvalent in terms of head loss. If the pad is close to the pool, you could go with 1, 2" or 2, 1.5" lines.

This should give you pretty close balance between suction and return. Adding ball valves at the pad to control flow will allow you to fine tune your flow rates.

[msm859]

I have two skimmers and the main drain with 3 - 2" lines going back to the pad which is @ 25' from the pool. There is a single 2.5" return line. Each line has a neverlube valve on it at the pad

There is no extra plumbing to divert the water to drain the pool via the main drain. Wouldn't there have to be a diversion valve to send the water somewhere other than back to the pool?

[mas985]

I have two skimmers and the main drain with 3 - 2" lines going back to the pad which is @ 25' from the pool. There is a single 2.5" return line. Each line has a neverlube valve on it at the pad

There is no extra plumbing to divert the water to drain the pool via the main drain. Wouldn't there have to be a diversion valve to send the water somewhere other than back to the pool?

Yes usually, a drain pipe is placed right after the pump with a manual valve so you can dump the water with either a hose or directly into a drain. You can also use flexible backwash hose to dump it on the lawn.

Also, it sounds like your plumbing is fine and will give you decent flow rates.