One pump or two?

15 years ago

Pool under construction is about 18000 gallons with a negative edge and associated trough outside the weir wall. On the return side, there is one pipe run in 2-inch pipe from the pad to six eyeball returns along the pool wall facing the negative edge. In addition, there is a separate 3-inch pipe run from the pad to three open 2-inch returns in the end pool wall to provide unimpeded high flow rates when returning water from the trough.

On the suction side, there is one pipe run to the pad from two drains in the floor of the main pool, in 3-inch pipe, and another pipe run to the pad from three drains in the trough, also in 3-inch pipe. Both runs use 2 x 45s rather than 90s where possible. In addition there is a dedicated 1.5-inch suction line to the middle of the long edge for a pool cleaner, and flow and return lines from the pad to ground-mounted solar panels. Filter will probably be a Pentair 520 cartridge filter.

I had been planning on using 2 Intelliflo VFs, one dedicated to the trough circulation and the other for the main pool circulation, but now that it is time to put my money where my mouth is I am wondering whether this is overkill and if an appropriately valved single Intelliflo VF would be sufficient.

While one might do the trick, what about the downside in terms of increased complexity and costs as regards automating flow/return set ups...? Should I just bite the bullet for a simpler life in the long term? How long can I reasonably expect the pump(s) to last?

I would much appreciate some words of advice from the wise regarding one or two pumps and pros and cons thereof...

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Comments (5)

poolguynj
15 years ago
How big is the negative edge?

Are you looking for sheeting down into the trough or dribbling down a wall and in?

How often and how long will the negative edge be running?

While the Intelliflow is one of the most efficient pool pumps available, if the edge is only going to run a couple hours and infrequently, a single speed Wisperflow may suit your needs as well. Food for thought. Is the extra energy used worth the delta in cost?

Scott
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kitamiman
Original Author
15 years ago
Thanks for responding poolguynj.

Inward sloping negative edge totals about 70 feet. Not looking to sheet - would rather water simply ran down outside of weir wall (quieter). Ability to adjust flow/overflow to achieve just that is a major reason that Intelliflo is attractive (as well as energy use). Would imagine we will circulate water from trough to pool for a short time each day to keep the trough water fresh, maybe with a brief boost to clear any trash stuck on the weir. In addition we would run after swimming each day to return overflow to pool and maintain the negative edge look.

Your post implies that you think two pumps would be a good idea, if not two Intelliflos. Given that the above trough routine is probably only an hour or two a day, leaving 22 hours a day to switch a single pump over to filtration/solar heating, why do you lean towards two pumps? Please understand that I am not questioning your opinion - just want to understand the pros and cons. I'm a pool virgin and want to get the best set up for an easy pool in the long term, even if it is at higher initial cost :)
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shellip, Scott is correct. There are several ways to plumb these pools. I have usually used a single pump system. As Scott indicated, it depends on the look you want on the backside of the dam wall and the length of the wall. I treat the basin as a big skimmer and pump everything thru the filter. A well built wall will only require 1-3 gpm/ft of wall to look good. Variable speed pumps work very well for these pool applications. It's also a good idea to run the pump while the pool is being used so the kids don't splash out so much water that the basin is overflowing. 2 pump system: One pump filters the pool water just like a normal pool. The second pump draws unfiltered water from the basin and puts it in the pool. The second pump should be running while the pool is in use(splash out reason I described above). It will also need to be run each day because the automatic water fill is placed in the basin. IMO the one pump system filters all the water all the time and I find it more efficient. Having a hand held or other electronic control is really handy for this application when you want to turn the pump on without having to go out to the equipment area each time. Biggest factor to good operation is sizing the basin correctly. Better to big than too small. You might ask your PB how he calculated the basin size. He should be able to tell you how much water will be in the basin with the pump running and about how much freeboard area they are allowing for. Good luck.
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golfgeek
15 years ago
kitamiman,
Your plumbing may dictate use of one pump or two. Some PB's put a skimmer in the pool and operate the pool filtration separate from the edge pump. Or, the basin acts as the skimmer and you can use a single pump for filtration and edge. It will take 1 to 5 GPM/FT of edge flow to get the look you want. Flow rates will vary depending on the material and workmanship on the edge.
The 4X160 Intelliflo works well because you can adjust the speed for the best efficiency of the edge and filtration.
Do you have an auto-fill on your project? This makes upkeep a lot easier.
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trhought
15 years ago
kitamiman-

I have a similar setup as yours....plus a few more water features. I have 4 pumps total but 2 do most of the work each day. The other 2 are just for pizzaz during parties.

The 2 workhorses are 2 speed pumps. One for the negative edge and pit and the other for the circulation pump. I also looked at a variable speed for each pump but could not justify the extra cost, especially since my return on investment was over 10 years at $.07/KWH. The 2 speed works fine for the negative edge...low speed provides a nice trickle throughout the day moving any surface debris to the weir and high speed is ran for short periods of time throughout the day to clear the weir. Integrating the variable speed to do both adds more complexity and moving parts to your job but can be done easily.

Also, I'm not a big fan of using a filter in the negative edge circuit. Our negative edge pit gets dirty especially this time of the year with all the pollen, tree husks and other debris from budding trees (It's essentially a giant skimmer). A simple scoop of this debris from the pit each day with a leaf net (a one minute task) is easier than having to clean cartridges more frequently in my opinion. Just thought I would mention this if you were thinking about using a filter in the negative edge circuit.

Also, I see you mentioned running the negative edge after swimming....actually you will need to run the negative edge during swimming to keep the pit from overflowing. Our 2 speed at low speed is adequate for this (40 gpm). Also, highly recommend the autofill in the pit as golfgeek suggests for negative edge pools.

In the end, the choice is yours and there are obviously many ways to approach this. Your philosophy and particular application may be entirely different from mine but I thought I would share my experience when deciding this very same thing during our build a couple years ago.

Hope this helps.
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poolguynj
15 years ago
Yes, I think you need two pumps.

How big are the pool and trough in terms of gallons.

Scott
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One pump or two?

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One pump or two?

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kitamiman
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