is 1/2 hp pump too small for 18" sand filter?

[singingpond]

Hi, I've posted a previous thread which included the question in the subject line above:
http://www.troublefreepool.com/threads/84519-asking-advice-pump-filter-upgrade-for-EasySet-type-pool
but thought it might work better to post the question with its own subject line.

Our existing pump is a Krystal Kleer model #51 (Intex pump/filter combo), looks like this newer model:
http://www.amazon.com/gp/product/B004P3HCPE/ref=ox_sc_sfl_title_5?ie=UTF8&psc=1&smid=A2V87KZI7RGEC0

From what I find online, this is described as a 1/2 horsepower pump. It is also described as moving 2500 gph (probably an exaggeration of what it does in real life).

Is this size pump too small for an 18" sand filter?

I'm looking at this Hayward filter:
http://www.amazon.com/gp/product/B000EVSGRE/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A2N5I30GK5BT1C

I realize there would be plumbing complexities in connecting the pump to the sand filter, but that's not really my question at the moment.

Thanks!

 

[mas985]

I think you are opening a can of worms with trying to swap the filter. If you want a sand filter, then just get one of these:

http://www.amazon.com/Intex-28651-1...TF8&qid=1409928728&sr=1-4&keywords=Intex+pump

And sell the old one.

 

[singingpond]

The 28651 is the other option I'm considering. It's just tempting to get the slightly larger Hayward sand filter (for not much more money than the 28651) to start moving away from the Intex equipment. If our current pump lasts another year or two, then we could upgrade the pump also in the future.

However, if a 1/2 hp pump just doesn't work with an 18" filter from the outset, then there's no point in pursuing the idea further.

Could you elaborate on the 'can of worms' you see? Is it the small size of the pump? Or the fact that no specs are available for it (none that I can find, anyway)?

 

[mas985]

The Intex series of pumps are designed specifically for the filter attached so there is no telling what can happen if you try a different filter. I am not sure you can even do it because of the way they connect the filter and pump so you may end up with a lot of leaks. Plus the pump may not be large enough to backwash the filter properly. I just think the risk is much higher than the reward. A 2" difference in the filters isn't going to matter much.

 

[scooperhsd]

If you want to swap out the Intex stuff - do it all at once - that way you will minimize any problems . and a 1/2 HP pump would be plenty - just don't go overboard on too large a pump.

 

[singingpond]

Swapping everything at once certainly makes sense. However, it costs more money up front, unless I opt for the Intex sand filter combo (28651). That is probably the most sensible approach, in many respects.

So, a 1/2 hp pump (like Hayward or Pentair) is plenty for an 18" sand filter (in your opinion, scooperhsd)?

If I understand the reservations expressed by mas985, it's the fact that our current pump is Intex that is a potential problem in running a different filter... not so much the rated size of the pump... I don't really see the greater leak hazard though -- I would probably just attach the output fitting of the existing pump/filter contraption to the (new) sand filter. Some transitional fittings would be needed in the plumbing, I'm sure, because of different sizes/standards at the two ends.

Thank you both for the information and opinions!

 

[mas985]

If you are going with both a pump and filter, I would look at one of the combo units. Here is a decent one:

http://www.amazon.com/Pentair-PNSD0060DP2160-Dollar-Aboveground-Blow-Molded/dp/B008HYKWJK

 

[singingpond]

If you are going with both a pump and filter, I would look at one of the combo units. Here is a decent one:

http://www.amazon.com/Pentair-PNSD0060DP2160-Dollar-Aboveground-Blow-Molded/dp/B008HYKWJK

If I'm reading that right, that's a setup with 250 lb. sand filter, and a 2 hp motor (it does say on Pentair site that it's a 2 speed motor). I suspect this is overkill for my 5500 gallons . I'd be scared (or amused) to see what a 2 hp pump would do.

Maybe this is more to scale, 3/4 hp, albeit single speed?
http://www.amazon.com/Pentair-PNSD0...qid=1410269317&sr=8-1&keywords=PNSD0035DD1160

 

[mas985]

You can but you don't get the two speed with that model and I think that is more important because you can run most of the time on low speed.

Also, keep in mind, the 2 HP that comes with the other setup is SPL rating which means it is the same "size" as a 1 1/2 HP up rated pump which is the same as a 1 HP full rated pump so you can't always judge a pump size by the label. In fact that pump has lower flow rate than a 1/2 HP Whisperflo and 1 HP Superflo. For your setup, the flow rate for the 2 HP would be around 51 GPM and for the 3/4 HP would be around 47 GPM so not much different.

 

[singingpond]

Thanks for the added explanation. Where can I find that sort of detailed information about the various pumps? The table (http://www.pentairpool.com/products/aboveground-systems-sand-sand-dollar-filter-systems-148.htm) I found at the Pentair website just had an indication that the 2 hp pump is a 2 speed model, but none of the other detailed information that you mention. It just says 60 gpm, which I imagine is what it does at its higher speed? For the 3/4 hp model, the table lists 35 gpm in the same column.

I did do a Google search on the model number and "specs" but didn't find many details -- maybe I just didn't look hard enough... ?

 

[mas985]

I have information from many sources that I have put together in a set of spreadsheets (see signature) that you can use to determine operating points for many different pumps. The primary data source is from the APSP and CEC which have measured pump data on their web sites but not for all pumps so I augment that dataset with theoretical pump data. However, if you want a simple comparison, here is a table that is in the Hydraulics 101 sticky in my signature.

 

[singingpond]

Thanks!! I'm continuing to read -- your Hydraulics 101, and other material on the web. Why do the manufacturers make it so hard to extract this info!? I think the pump on the Sand Dollar system you linked (the Amazon link) is a Dynamo pump -- even making that connection is a roundabout process, via replacement parts lists on Pentair site. Do the manufacturers just assume potential purchasers don't want to know anything on the technical side (rhetorical question, I guess) Coming from a household where we peruse data sheets for light entertainment (only half kidding), this absence of information strikes me as rather bizarre.

 

[mas985]

I think you are right. You might want to go with the PNSD0060DO2260 because that has the 1 1/2 HP SPL rated two speed pump with the same filter.

 

[singingpond]

Let me try one other tack, realizing we're in the theoretical realm... Assuming that money is no object, and that I'm not bound to prepackaged pump/filter combinations --

What is a good size sand filter for this relatively small pool? The chart in the Hydraulics 101 link doesn't go any lower than a 2.64 sq ft sand filter, which makes me wonder if nothing smaller is really recommended, no matter how small the pool volume.

What is the best pump size (in terms of low energy use, while still large enough to backflush the filter)? I'm assuming the ideal recommendation would still be for a 2-speed pump.

If I know what might be recommended as an ideal setup, that will be food for thought in terms of figuring out real world compromises.

 

[mas985]

The reason that the chart does not go below 2.64 sqft is that there is really no pump that can produce that low of a flow rate (on full speed). So there would be a risk of either damage or under performing filters. Even that filter size is really too small. The minimum is probably a 3.14 sqft.

Also, when it comes to filters, bigger is usually better for both performance and cleaning frequency so you want to always error on the side of a bigger filter.

For backwashing a filter, there are recommendations for 15 GPM/sqft but I believe you can adequately backwash a filter at lower rates as long as the filter flow rate is lower than the backwash rate.

If pool size is not a consideration, then first choose the smallest two speed pump you can find which is the 3/4 HP Dynamo and produces about 45 GPM on AG plumbing. Then the minimum filter size for that pump would a 3.14 sqft filter. Those two would be properly matched for both filtering and backwash.

 

[singingpond]

Thank you!! This is very helpful, especially the explanations behind the recommendations!