Sand Filter Sizing

[mas985]

I think you are better off with the PNSD0060DP2160. I says it has a 2 HP pump but in reality it is SPL rated which means it is identical to the 1 1/2 HP pump. But the flow rate is not all that much higher than the 1 HP:

51 vs 48 GPM on Curve A

67 GPM vs 61 GPM on Curve C

The big difference is the filter size (~2x). So the PNSD0060DP2160 is bit more oversized for the pump vs the PNSD0035DE2160.

 

[pooldv]

The 3/4 hp pump max is 60 gpm. Smaller 2 speed pump and bigger filter is good. Yes, that is all Mark's stuff, he is a pool pump genius. Listen to him over anyone else, like me.

 

[Schnozz]

pooldv....how did you arrive at 60 GPM as the max from the chart.. I don't think I understand how to read it. Or is that number more from your experience in understanding pump gpm?

 

[Schnozz]

Pentair lists in the specs that PNSD0035DE2160 has a 16" sand filter while the PNSD0060DP2160 has a 22" sand filter. (Amazon has it incorrectly listed as a 32" sand filter instead of a 22"). That seems undersized from my limited knowledge base. And, it's still seems much smaller than the table in Hydraulics 101 would recommend. I'm not going to stress about why these companies undercut the NSF standards for sand filters as presented in the table.

It's probably just old thinking, like bigger is better with regards to pumps and that the pool water must be turned over once or twice a day for every pool in every location or that you can never have too much CYA. LOL

I think I have enough information ( I believe I said that in another thread) to make an informed decision..Ill probably stick with a larger pump/motor than the 3/4 HP just in case I upgrade. I f I don't go with a factory combination, I may run my selection as well as the GPM flow charts by you guys before I make the pruchase so as not to blow $600.00 on a bad decision. I really appreciate your input. Hope others got a chance to check out this thread. Lots of good clarifying information...

Im sure you'll here from me again.

 

[pooldv]

pooldv....how did you arrive at 60 GPM as the max from the chart.. I don't think I understand how to read it. Or is that number more from your experience in understanding pump gpm?

So, the chart reads almost 70 gpm max flow. But, that is with not much head pressure. So, I went down to the next line, which is 60 gpm.

 

[Schnozz]

Mas..

So, for my own clarification.......Where the Pump Curve Graph (from the pump manufacturer) for the pump I select intersects the Plumbing Curve Graph (In the Hydraulics 101 Sticky. I believe you said in an earlier post that you generally use Curve A for AGP's.) This intersection is the point I use to calculate optimal GPM Flow through the Sand Filter and select the proper size (sq-ft or inches) to use for my needs, and that matches up best with the pumps GPM Flow. Maybe a 10% to 15% bigger sand filter for good measure?

Did I understand that correctly?

Not sure why I need to know that, your spreadsheet does all that...

 

[Schnozz]

I'm sorry...I want to make the point about matched sets of pumps and filters, again. Looking for a response and some clarification. For example...

Line 58 of the Pump Database I was provided earlier says that the Hayward Matrix 2-Speed 1.5 HP Pump (SP15922S AG) requires a sand filter with a Effective Filtration Area of 4.4276 sq-ft at 53.04 GPM.

Hayward sells that pump in combination (S230T932S) with a 23" Filter (S230T). That sand filter has an Effective Filtration Area of 2.7 sq-ft at 54 GPM.

Isn't the 23" filter (S230T) with an Effective Filtration Area of 2.7 sq-ft, provided in the combination pump/filter setup from Hayward, undersized for the 1.5 HP 2-Speed Pump (SP15922S) it's paired with by NSF Standards? NSF recommends a Sand Filter with a 4.4276 sq-ft Effective Filtration Area.

I hope I'm not beating a dead horse. But either the NSF standards for sand filters are unnecessarily high or the equipment companies are selling combination set ups with either undersized filters or oversized pumps. Both those scenarios are detrimental to effective pool maintenance. All the equipment companies seem to do the same thing. A filter with smaller Effective Filtration Area than what is recommended by NSF Standards.

I realize there may be other factors to consider ( distance of equipment from pool, changes in elevation and pool size) but I can't see those factors making such a large difference in variation in the sizing of pump and filter between the NSF Standards and Manufacturers combinations.

Or, am I not understanding the spreadsheets provided here or the spec sheets provided by the manufacturer?

I can't thank you guys enough for taking the time and sharing your expertise with us when considering our questions.

 

[mas985]

Line 58 of the Pump Database I was provided earlier says that the Hayward Matrix 2-Speed 1.5 HP Pump (SP15922S AG) requires a sand filter with a Effective Filtration Area of 4.4276 sq-ft at 53.04 GPM.

At 53 GPM, you could go as small as 2.65 sq-ft using 20 GPM/sqft. 3.5 sq-ft using 15 GPM/sqft I am not sure where you get 4.4 sqft. Yes, bigger is always better but not necessary. Damage to the filter probably wont occur until you reach well over 25 GPM/sqft.

However, Curve A may be overly optimistic for smaller sand filters. As the filter gets smaller, head loss increases and flow rates decrease so in fact, the Matrix may very well have flow rates less than 53 GPM.

Also, I would not get overly concerned about the GPM/sqft but focus more on the size of filter you may want. Larger filters offer less frequent cleaning and that is probably more important than the exact GPM/sqft. Remember too that with a 2 speed pump, you can run on low most of the time anyway.

 

[Schnozz]

OK....I can see that..

If I remember Flow at 20 GPM per sq-ft of Sand Filter and match that with the pump GPM, I should be good..I'm just trying to make sure I don't have too much pump for the sand filter selected. I'll probably purchase a combination matched by Pentair or Hayward rather than buying them seperately anyway, but I didn't understand what I thought was a discrepancy in the figures I was seeing.

I got 4.4 from Pump Database - Google Sheets Line 58, Column AF, Titled SAND. The figure in that box is 4.4.
I thought that was Sand Filter Size in sq-ft for the pump on Line 58? Not true?

I'm apparently trying to get a Masters Degree in Pump/Filter Theory by means of a few dozen posts.....:study: Interesting, considering I'm a guy with an Intex Temporary Pool set-up in his first year of pool ownership.

Thanks for your time and talent...

 

[mas985]

Unfortunately, I had not updated that tab when I changed the format of the database so it was not showing correct data. Now it is. But again, that uses the more conservative 15 GPM/sqft.

 

[Schnozz]

Mark:
I cannot thank you enough for your help with this. :handshake: And all of you who responded as well. I guess it's what the site is truly all about.....

My plan over the next few weeks is to layout my proposed location change for the equipment (including hard plumbing, solar on the roof and an upgraded, meaning larger AG pool) and try to figure head loss and appropriate pump/filter size. Then I will select a pump and filter combination based on this research from Pentair or Hayward (my personal preferences) and run it by the forum to see if my calculations are correct and to see how much I've learned. Maybe you CAN teach an old dog new tricks.;-)

I'll download the spreadsheet again for my files. Thanks for the update..

Thanks again to Mark, pooldv, denniswiseman, JamesW, singingpond and to everyone else who took the time to help me understand.....(I know the thank yous make it sounds like I'm dying. I'm not, just finished for now)......Bob