New Pool Question

[underwater]

Hey all,
Posted something similar in another thread, but I thought I would ask here as well.
Getting bids for new pool (16x32 diving grecian). I have estimated the capacity at about 20k gallons.
Both builders are bidding a DE filter, but it seems awfully big (FNS Plus 48). I want DE, but do I really need one this big?!?!?!?!
One is bidding a 1 1/2 hp pump and the other's is a 1 hp. I thought surely a 3/4 would get it , but what do I know. I bought a Blue Pearl so I won't need a pump for a cleaner. I'm a little confused. I have just about talked myself into a Whisperflo pump because I really want a 2 speed. They are both bidding a Challenger which appears to be single speed. Any ideas on a pump/filter combo recommendation? I'm all ears. :-D
Thanks in advance.
UW

 

[JohnT]

Bigger is better when it comes to filters. The larger filter will go longer between backwashes, which can be especially handy if you have an algae bloom.

A 1 HP pump will do the job. 2 speed would be nice though.

I suspect your pool is less than 20K gallons, as I have a 20X36 diving grecian that holds about 21K gallons.


A little more detail on the pool location (city/country? trees? climate? bather load?) will help with the recommendations.

 

[spishex]

You can get both the Challenger and Whisperflo in 2 speed models. The Challenger is a little less expensive and easier to work on, but the Whisperflo is more efficient and will move more water.

As for the filter, with DE and cartridge filters it's always nice to have a bigger filter than you need. It will mean you're changing the DE out less often, and that's a big plus. You'll need about 1.5-2 GPM per sq ft on that filter (48 sq ft), so 72-96 GPM. That will give you a 4-5 hour turnover and would probably require a 1hp Whisperflo or a 1.5hp Challenger. You can get away with a smaller pump, but you'd want to size the filter down with it and that would lead to more filter cleaning.

Low speed filtration works great with sand and cartridge filters, but you need enough pressure to keep your DE in place with a DE filter. The only two-speed + DE installations that I can remember working on have been on spas, which can get away with a smaller filter (we don't see a lot of DE around these parts). Perhaps some of the others have dealt with this issue more.

 

[mas985]

You'll need about 1.5-2 GPM per sq ft on that filter (48 sq ft), so 72-96 GPM. That will give you a 4-5 hour turnover and would probably require a 1hp Whisperflo or a 1.5hp Challenger. You can get away with a smaller pump, but you'd want to size the filter down with it and that would lead to more filter cleaning.

I'm not sure that I agree with this statement. My understanding is that there is generally no minimum flow rate for a filter only maximum ratings. In fact, filters will work better at lower flow rates than higher flow rates. So you should not need to reduce the filter size with the pump HP. However, the opposite may be true.

Having a larger filter will clean better and reduce the time between cleanings but may require more DE at the time of cleaning for recharging. The only downside is the cost but the cost difference is well worth it IMHO.

 

[JasonLion]

What I have seen with two speed pumps is that in most cases you need to run the pump on high to coat the grids after adding DE or bumping. Once the grids are coated it is usually fine to run on very low speeds.

 

[spishex]

What I have seen with two speed pumps is that in most cases you need to run the pump on high to coat the grids after adding DE or bumping. Once the grids are coated it is usually fine to run on very low speeds.

That's kind of what I was thinking. I'm OK with slower being better in general, but I'm just not sure what the minimum flow rate per square foot would be to evenly coat the grids.

The 1.5-2 GPM range I gave was what Pentair lists as the operating range for DE based on NSF filtration requirements for commercial pools. The corresponding rates for Sand and Cartridge are 15 and .375 GPM respectively.

I just gave Pentair a buzz to see what they had to say. Their guy told me the minimum for the FNS 48 would be 30-40 GPM.

 

[gtm]

The 1.5-2 GPM range I gave was what Pentair lists as the operating range for DE based on NSF filtration requirements for commercial pools. The corresponding rates for Sand and Cartridge are 15 and .375 GPM respectively.

Is the "15" correct for sand filters? Should that be "1.5"? Mine is not usually that high, which is why I'm worried.

 

[mas985]

30-40 GPM will be well exceeded by any size pump at full speed. Even a 3/4 HP Whisperflo at half speed will deliver over 30 GPM for a well designed plumbing system not that I am suggesting to use half speed for grid coating but one could. So I think a 3/4 HP 2 speed Whisperflo would work just fine with that filter.

 

[mas985]

Is the "15" correct for sand filters? Should that be "1.5"? Mine is not usually that high, which is why I'm worried.

NSF design guidelines are for commercial pools which have much different goals than a residential pool. High turnover rates is usually desireable in a commercial pool. This often is contradictory to the filter optimum flow requirements. I believe those guidelines were developed for the intent to allow for the maximum turnover while still maintaining adequate filtering capability since higher flow rates result in poorer filter performance.

A residential pool doesn't require the turnover rates of a commericial pool so the design criteria will be different. For general circulation of a residential pool, lower flow rates result in better filtration for the same number of turnovers and lower energy use. Therefore, the primary design goal should be the lowest flow rate possible to achieve the desired turnovers in a day.

Here is a very good tutorial on pump sizing which shows how to determine the best flow rate operating range. You will note that the minimum flow rate is usually set by the turnover rate and the maximum flow rate is below filter's maximum flow rate. Generally, the problem isn't reaching the minimum flow rate but exceeding the maximum flow rates. The smallests pumps can usually satisfy the turnover requirement and stay below the maximum flow rates.

Bottom line, no worries.

 

[spishex]

The 1.5-2 GPM range I gave was what Pentair lists as the operating range for DE based on NSF filtration requirements for commercial pools. The corresponding rates for Sand and Cartridge are 15 and .375 GPM respectively.

Is the "15" correct for sand filters? Should that be "1.5"? Mine is not usually that high, which is why I'm worried.

That's 15 GPM per square foot, so for your filter you'd need about 37.5 gpm. As has been said, filtering slower than that is fine, but in the case of a sand filter you'd want to be able to achieve that (15 gpm/sq ft) in order to be able to backwash properly.

 

[underwater]

30-40 GPM will be well exceeded by any size pump at full speed. Even a 3/4 HP Whisperflo at half speed will deliver over 30 GPM for a well designed plumbing system not that I am suggesting to use half speed for grid coating but one could. So I think a 3/4 HP 2 speed Whisperflo would work just fine with that filter.

Got all that, but after doing some checking I found that the 3/4 Whisperflo is a 115V only. According to the specs on Pentair's site, it will draw 4.7 amps at low speed where the 1HP is a 230V and will only draw 3 amps at low speed. So I would be better off (efficiency-wise) to go with the 1HP, correct? Then we know this pump will work fine with the filter, agree?

Now if someone could just tell me the difference between those two panels in my other post
Thanks again for all the help.
UW

 

[JasonLion]

There is a strange property of the WhisperFlo line. The single speed line is available in a high efficiency version that is really amazing. But the dual speed line is only available in standard efficiency. The net result is that the high efficiency 3/4 HP single speed is very close to the 1 HP dual speed on low in overall efficiency, not quite as good but closer than you might imagine.

Also, you can't compare amps at 115 volts to amps at 230 volts one for one. Each 230 volt amp uses twice as much electricity as a 115 volt amp does. The 1 HP at 230 volts and 3 amps is drawing the same amount of electricity as a 115 volt 6 amp unit would draw.

 

[spishex]

If you're looking for efficiency first and foremost, take another look at what mas was saying in the other thread about the Intelliflo. More expensive up front but it's much more energy efficient and will make this whole discussion on flow rates a moot point since you'll be able to run it at whatever speed you like from 1/2 to 3 HP.

 

[underwater]

If you're looking for efficiency first and foremost, take another look at what mas was saying in the other thread about the Intelliflo. More expensive up front but it's much more energy efficient and will make this whole discussion on flow rates a moot point since you'll be able to run it at whatever speed you like from 1/2 to 3 HP.

I have decided you are right about that. Question, though, there is a high perf and a regular and the Intellipro (sta-Rite brand). Should I basically go with which ever one I can get the cheapest?
Since I have about decided to build/contract this thing myself , I can use some of the savings on it.
I called to check on a kit yesterday. The guy was very nice and kinda respectfully tried to steer me away from a DE filter. The periodic maintenance doesn't bother me. Aside from that why would it not be such a good idea?
Thanks again and please keep 'em coming.
UW

 

[JasonLion]

The IntelliFlo costs much more up front, but it will save a significant amount of electricity. In many areas, depending on your electric rates, the long term savings more than pays for the up front costs. The IntelliFlo also has the advantage of starting up for a short period on a relatively high speed and then ramping down to the set speed. That helps keep the DE grids coated.

Each kind of filter has it's advantages and disadvantages. All three of the major kinds of filters (sand, cartridge, and DE) will work in nearly any situation. The differences mostly have to do with small differences in water clarity and how much trouble they are to keep clean. In a few areas DE filters are required to use DE recovery tanks, so no DE is released into the environment. I personally like sand filters, but DE should work just fine for you.

 

[spishex]

DE means more maintenance (though with proper pool care it won't be much) and some people are averse to it because the powder itself is a carcinogen and there are sometimes restrictions on whether or not you can discharge it through your waste line. Be sure you have a separation tank on your backwash line if code requires it and wear a mask when you're recharging the filter.

As for the Intelliflo, you have a few different options. First, Sta-Rite vs. Pentair. I'd go with the Pentair just because I prefer the Whisperflo housing to the Max-e-Pro, but they're both made by Pentair and both good pumps.
Your next option is Variable Speed (4x160) vs. Variable Flow (High Performance). It's a few extra bucks, but the Variable Flow model is a much smarter pump. Rather than just maintaining a set RPM, the VF will monitor your flow rate and change RPM to compensate for changes in the system such as a filter that is getting dirtier. Again, both good pumps but the VF more fully realizes the potential of the motor.

 

[underwater]

EXCELLENT INFO!
Thanks.
I have 2 more questions and then I promise I will leave you all alone (for a little bit). The guy also recommended an Aqua Genie.
It seems like that would probably work fine on this pool. What are your thoughts?
The other one is - he said unless local codes call for it, I didn't need/have to put in a main drain in the deep end. I have never heard of this. Good idea/bad idea? Why? I like the idea of not having to do that since I will be doing this myself, but if I'm gonna need it . . . . . . might as well.

Thanks again. I might catch on after all.
UW

 

[spishex]

I think the aqua genie is inane. It's just made to sell the little chlorine canisters that go with it. You can get a skimmer that is plumbed into your return line to get more of that elusive "Skimming Action", but even those I find to be of little use.

Going without a main drain is doable, and it is nice knowing all your plumbing is accessible. The two drawbacks I find with no-m/d systems are not being able to run the pump when water is low (you can run a line into the skimmer from the wall just below the skimmer opening to solve that) and increased accumulation of dirt and heavier debris that falls before being skimmed (the suction side cleaner will help with that).

All things being equal I'd rather have a [dual, VGB compliant :-D ] main drain, but you can live without if you compensate for it properly.

 

[JasonLion]

There have been a couple of comments from Aqua Genie owners here. The general reaction has been that it is cool but perhaps not quite as amazing as they make it out to be. In a couple of cases, having an Aqua Genie has created secondary problems. Winterizing can be slightly more difficult and there are disadvantages to not having a standard return fitting.

It is nice to have a main drain, but hardly essential. I have gone several years without one and never really had any problems. One the other hand, if I were building from scratch I would probably get one. It is less common to see main drains on vinyl liner pools because the extra holes in the liner give you more places where you can have a leak (though leaks like that are actually very rare).

 

[underwater]

Those thoughts are kinda the way I felt about it. Think I'll go more the "traditional" route. I like returns AND the main drain. Although, I am curious, why would you want to run the pump when the water is below skimmer level anyway.? Never crossed my mind.
With all that being said, is there a general consensus on where to order these kits from?
UW