18,000 gallons on a DIY build.

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ImLon2

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Apr 13, 2018
42
Granite City, IL (St. Louis area)
I have everything picked out for the pool build in late spring except for the pump.
It’s going to be a 20x40 Mountain Loch style from an online supplier with a 10’ tanning ledge, 42” to 57” deep.

2 skimmers, 2 main drains, 3 returns (may add 2 more to push water across tanning ledge to clear debris) Sand filter, Pentair salt generator, 140 btu heater.

Pump will be 30’ from center of the pool, so not sure on head loss. I do plan to run 2” lines with long sweep 90° elbows to the outlet. Do I need 2” on the returns or is 1.5” fine?

I will run the pump 8-10 hours using 20,000 gallons to make things easy I’m at 42 gpm on 8 hours/day and 33 gpm on 10 hours/day. In the past I had a 1hp on my 15,000 gallon pool with no issues.

What pump size would you suggest? Single speed, dual speed, VS. If VS can I run the pump on a timer or is that all controlled from the control board on the pump?
 
I have a 3hp VS that i run 24/7 at low RPMs. We like the look of the moving water and its cheaper than running 2/3 speed for a few hours a day. The added bonus is that my pool is always skimming and always producing FC with the SWG. It makes care easier overall but also somehow saves money. The onboard controller has programable times and speeds if we chose to use them, just walk over to the equiptment and press a few buttons. Or if you wanted full automation, you could control it all from your cellphone. The sky is the limit.

I have a 20X40 rectangle with 2 returns. 'Mountain Loch' sounds like it would be more free form than square. With my rectangle, 2 returns in the shallow end is plenty. If yours has alot of curve it could react differently on the backside of the inward curve. Although my straight walls work great with just 2 returns, my stairs are a dead zone for debris. Both the floating and sinking kind. It stinks because its the first place most people go to and its got sand/leaves within minutes of cleaning them. For this reason i would recommend returns for the stairs along with the tanning ledge returns. Just enough power to move it all out to where the regular flow can get it.
 
I'm curious why the 57" depth? That's gonna be a 4 and a half ft deep pool with water? You dont need drains especially in a shallow pool they stink to step on and do nothing overall. Get a robot save the effort of putting them in. You want opposite on piping. 2" home runs for skimmer/drains and 1.5" home runs for returns. You want 4 returns for that size pool minimum AND you want returns to clean ur stairs and ledge so 6 at least. You can stack pairs of returns so you have 3 home runs and use 2" pipe then and go 1.5" after the split off. Its nice to have valves individually you have total control and balance and you can only do it once at install. VS is the way to go nowadays
 
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2,

In general, for residential pools, the size of the pool has nothing to do with the size of the pump..

VS pumps come in two basic sizes.. 1.5 HP and 3 HP give or take a little bit.

I am a fan of having a large VS pump, so that you can run it as slow as possible and still move a lot of water.

The "Gold Standard" of VS pumps is the IntelliFlo... I would recommend the 011018 or the newer 011028.. Both are VS only pumps.

The only warning is never, and I mean never... buy a VS pump with the SVRS option... Safety Vacuum Release System (SVRS).

Just for reference... I run my IntelliFlo at 1200 RPM, 24/7, for less than $20 bucks a month.. There is no requirement to run 24/7, just an example of the low cost to run.

Thanks,

Jim R.
 
Won't be much swimming going on in that shallow of a pool. Scraped knuckles for sure! 3' water height is very uncommon. If you're set on a shallow pool I'd suggest it be 4' to 5'... perhaps a sports pool where it goes 4-5-4.

Maddie :flower:
 

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If you have kids the 6ft end will be the fun cannonball end. The pool you propose is a wading pool. As long as you thought it thru well go for it. I agree that you cannot swim laps in 3ft depth or jump into 4.5ft. Me, I would make a steep bowl and leave a large part shallow if there are kids in the picture
 
borjis said:
big difference between gas heaters and heat pumps.
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ImLon2 said:
Me too!! Glad you brought it up.
Click to expand...

There are a few big differences and they can be drastic based on how you plan to use the heater.

A heat pump is best when the air/water is already relatively warm and you want it warmer. Ideally, think of somebody in Florida who wants to make their 78 degree pool warm to 90 degrees. Under 70 degrees in either air or water temp, and the heat pump will struggle to make any difference at all. Once the pool is already warmed, the heat pump is more efficient keeping the pool warm, providing the ambient air temp is 70 degrees or higher, but running 24/7 can cost a small fortune early/late in the season.

A gas heater can have triple the BTUs of a heat pump and therefore can heat the pool much faster, but once the pool is warm, it uses more energy than the heat pump to maintain the warm pool, everything else being equal. It is ideally suited for a situation where you want to swim occasionally on a early/late season weekend and not spend money between uses. If you spent $100 to be able to swim thanksgiving weekend with your guests, it would be money well spent.

Of course there are many variables that could change the equation, but this is just the general overall comparison. There have been people simply with no access to one of the energies at their pool site. Their choice was made for them and it was still better than no heater. For everybody else it is best to first decide how often they plan on using the heater, and what the local energy costs will be to do so. Then compare that to what your local weather temperatures will allow. For myself in NY, i simply cannot use my heat pump for 5 months out of the year. It just wont work.
 
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Newdude said:
There are a few big differences and they can be drastic based on how you plan to use the heater.

A heat pump is best when the air/water is already relatively warm and you want it warmer. Ideally, think of somebody in Florida who wants to make their 78 degree pool warm to 90 degrees. Under 70 degrees in either air or water temp, and the heat pump will struggle to make any difference at all. Once the pool is already warmed, the heat pump is more efficient keeping the pool warm, providing the ambient air temp is 70 degrees or higher, but running 24/7 can cost a small fortune early/late in the season.

A gas heater can have triple the BTUs of a heat pump and therefore can heat the pool much faster, but once the pool is warm, it uses more energy than the heat pump to maintain the warm pool, everything else being equal. It is ideally suited for a situation where you want to swim occasionally on a early/late season weekend and not spend money between uses. If you spent $100 to be able to swim thanksgiving weekend with your guests, it would be money well spent.

Of course there are many variables that could change the equation, but this is just the general overall comparison. There have been people simply with no access to one of the energies at their pool site. Their choice was made for them and it was still better than no heater. For everybody else it is best to first decide how often they plan on using the heater, and what the local energy costs will be to do so. Then compare that to what your local weather temperatures will allow. For myself in NY, i simply cannot use my heat pump for 5 months out of the year. It just wont work.
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I do not plan on extending my pool season but maybe 1-2 weeks on each end of the swimming season we normally have. I will have a solar cover on the pool for 1. to help not lose as much heat at night, and two to help heat the pool during the day with the sun. In St. Louis we get from Memorial day (if your lucky a week or two before) and Labor day (if your lucky a week or two after).

I have had a pool for the last 25 years, we just built a new house, and plan on bumping up the size of the pool and this will be the first time with the heater. I'm just looking for something to help it get a little warmer here and there. We like the pool around 88-90° depending on the time of day we are swimming. I do know with a heat pump it does not heat no where near as fast as a gas heater so it will take sometime to get adjusted.
 
ImLon2 said:
I do know with a heat pump it does not heat no where near as fast as a gas heater so it will take sometime to get adjusted
Click to expand...

If it can physically catch up at all. The larger pool makes it harder for the smaller (btu wise) heat pump to raise the temperatue. If you had a 10k pool and a 140k btu heater it would work better. I have a 20x40 with 35k gallons and the only way my 120k heatpump will work early/late is to leave it running 24/7. Which costs a small fortune. If i was to turn it off for 2 weeks on Sept 10, i would not be able to warm the pool back up. (As an example, on the average year).

You are also right that the solar cover is an absolute must with either system. It cut my elecric cost roughy in half down to $400 a month.(for just the heater). Again, with different regional costs on different years with different weather/temperature, this can vary greatly.

I have a similar climate to yours and i wish i had gotten a gas heater. My neighbor had one and i knew she spent alot on gas. The delivery truck was at her house every 3 weeks. So when we asked the PB he said the electric heaters were much more efficient than they used to be, which was complete truth. They still cost a fortune to run 24/7 though in our weather. For my families use we would have been better suited with gas. Just turn it on the night before and if we were busy for 2 weeks between swim weekends, it was free by turning it off. In my case i had to leave it running the whole time we ended up too busy to swim once school started back up.

Im most likely going to end up with solar power at some point. That will change my equation again, where i will care much less about how much electric goes to the heater

There are also people that will only swim in 90+ degree water and only during the warmer months. The heat pump is the more economical/efficient of the two for them.

There are 100 variables to the equation. Write down all your pros/cons and go from there. Everybody has a different answer but this will help you get where you need to be.
 
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