another cartridge filter question

I've been browsing around the Internet, trying to find out more about pool cartridge filters and flow rates. Came across a Unicel FAQ:

http://www.unicelfilters.com/retaile..._flow_rate.asp

which describes maximum flow rate of 1 GPM per square foot of filter area. I found similar numbers at one or two other websites, so I assume this number is in the ballpark at least.

Running numbers for our 1500 gph pump (came with a 18' x 48" Summer Escapes donut pool) --

1500 gph = 25 gpm

The standard cartridge filter that fits in this pump housing has 5 sq. ft. of filter area.

So, that means a flow rate of 5 gpm per square foot of filter area (25/5), if I'm plugging in the numbers correctly? That's obviously a lot higher than 1 gpm...

If these numbers are correct, that would help explain why the filter doesn't seem to be accomplishing much. Also, whenever I pull out the filter for cleaning, it has a large dirty spot right where the water intake hits the filter (water enters from the side, near the upper end of the filter), and some fainter dirt deposits distributed around the lower half of the cartridge (water exits from bottom center of the housing). The rest of the cartridge area still looks white, as if it isn't really participating in the cleaning process. Maybe that makes sense, if the pump flow rate is much higher than it really should be for the cartridge size.

We just put this pump in a few weeks ago (at the moment, it is filtering water in a 1000 gallon pool), and are observing its operation. The pump we used in previous summers was the smaller 600 gph pump that came with the 1000 gallon pool, and its filter cartridges always looked much more uniformly dirty when we took them out for cleaning.

This all makes me worry that the 1500 gph pump, and its associated cartridge filter, will do a very poor job once we set up the larger (18' x 48") pool. We do plan to try the better quality (Unicel or Filbur) cartridges, but that doesn't seem to solve the apparent flow rate mismatch.

I guess I'm hoping I made some dumb mistake in the calculations, and that the mismatch between pump and filter isn't quite as bad as it looks... ? Please feel free to point out errors in assumptions or calculations :)

Could something like this:

http://www.amazon.com/Hayward-C250-S.../dp/B00269IHBW

or this:

http://www.amazon.com/Hayward-C225-M...d_sim_sbs_lg_4

be put in downstream of the pump we have to provide larger filter area and better filtration (assuming we just get rid of the small cartridge inside the pump housing entirely)? I know there might be some plumbing issues in connecting stuff, but I'm sure we could figure that out. Just wondering if the idea is OK in principle?

I would still be happy to get some feedback on my question about larger filters...

For the moment, I've experimented with hooking up our two pump units (a 600 gph pump which uses a 2.5 sq. ft. cartridge, and a 1500 gph pump which uses a 5 sq. ft. cartridge) in series (with only one pump actually running) -- that way the filters in the two units are in series, and we get reduced flow rate and somewhat increased filter area. It's interesting -- this kludge does lead to noticeably better filtration (finally getting rid of dead algae that's been hanging around in the pool for the past three weeks or so). It also seems that the performance is almost as good when I plug in the small pump as when I plug in the larger one. For reference, this experiment is taking place on 1000 gallon volume.

This all makes me hopeful that a significantly larger filter area will really help. Comments on how large a cartridge filter we should look for (for future 6000 gallon pool) would be much appreciated.


On a different topic, how long does it usually take to 'escape' moderation? I've asked several questions about our pool and equipment, have made an entry in the Pool Chart, and have tried to post helpful comments in one or two other threads... is it just a matter of waiting a certain amount of time, reaching a certain post count, or what? I've read the sticky in the 'Getting Started' forum, but I'm still not sure if there is some step I've missed... I understand the reasons for moderation, but this certainly is the most lengthy moderation 'purgatory' I've ever encountered, among the various forums I've participated in over the years :)

I have read other posts that indicate that your type of pool is notorious for too small of a filter. Other advice includes "it'salways better to have more filter than you need". Filters and pumps get sized based on how many turnovers you want per day -usually a minimum of 1.

As far as moderation, - it's the height of the season and no doubt the Mods are really busy. (Either moderating or swimming). Wait a bit and if you don't get a response give them a poke by starting another thread. It says you are an "established user". You can escape moderation by suscribing. Use the $$$ you save not going to the pool store.

People with Intex pools are usually happy with the 2500 GPH pump/filter over the smaller pumps which just don't have the power for proper circulation and cleaning.

But for a 6000 gallon pool, you would want a minimum of 45 sq-ft but ideally a 90 sq-ft filter would minimize cleaning to once per season. So the 2500 GPH combo might be insufficient for this size pool. However, there are plenty of combo units made by Hayward and Pentair which would work well. For example, the PNCC0100OE1160 might be a good choice. If you want a two speed pump, I would go with the PNCC0150OF2160 which has a larger filter to match the larger pump.

You can check out all the Pentair combo units here:

http://www.pentairpool.com/pool-pro/...-system-26.htm

Quote:

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Originally Posted by mas985

People with Intex pools are usually happy with the 2500 GPH pump/filter over the smaller pumps which just don't have the power for proper circulation and cleaning.

But for a 6000 gallon pool, you would want a minimum of 45 sq-ft but ideally a 90 sq-ft filter would minimize cleaning to once per season. So the 2500 GPH combo might be insufficient for this size pool. However, there are plenty of combo units made by Hayward and Pentair which would work well. For example, the PNCC0100OE1160 might be a good choice. If you want a two speed pump, I would go with the PNCC0150OF2160 which has a larger filter to match the larger pump.

You can check out all the Pentair combo units here:

http://www.pentairpool.com/pool-pro/...-system-26.htm

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Thank you for the comments, and for the link!

What you say tends to confirm that the stock filters that come with the Intex-type pool packages, especially the filters for the larger volume pools, are woefully undersized. I don't really mind cleaning the filter a few times during the summer, but that still seems to put us in the realm of ~50 sq ft filter area (the stock filter is 5 sq ft, so that's apparently too small by an order of magnitude -- no wonder the darn things don't work well).

The Pentair units certainly look nice. However, having spent only $199 on the pool package (Sam's end-of-summer price for the 18' x 48" Summer Escapes pool), we're not immediately likely to spend $500+ on a better pump/filter combo. I had been thinking of getting just a new (larger) filter and putting it in downstream of the existing pump -- that could be done for <$200. Is there a major flaw with that approach?

In terms of complete packages, what about something like this:
http://www.poolbargains.com/above-gr...w-element.html

Is this likely to be a total piece of junk at the price?

Quote:

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Originally Posted by nefretrameses

...
As far as moderation, - it's the height of the season and no doubt the Mods are really busy. (Either moderating or swimming). Wait a bit and if you don't get a response give them a poke by starting another thread. It says you are an "established user". You can escape moderation by suscribing. Use the $$$ you save not going to the pool store.

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Thank you for your comments.

Yes, my user description has apparently changed, and I can now post directly, which is nice.

I agree that a subscription would be worthwhile -- there certainly is a great deal of valuable information here. However, I wouldn't be saving anything on pool store purchases; haven't set foot in one yet :) As owners of a 1000 gallon donut pool, we're pretty much on the penny-pinching end of the spectrum, and our pool expenditures are only gradually growing as we learn more about necessary pool maintenance.

I don't know much about Advantage Manufacturing so I can't really comment on performance or reliability of that combo unit. But given the price, you can't expect too much.

http://www.advantageman.com/category_s/36.htm

I noted in another thread that you are high in DIY, and short on $$. Same situation here.

Knowing that Intex/Summer Escapes and many other low cost starter pools have very poor filtration/circulation, I've been slowly working on my 15' x 48" Intex, trying to work out some of these inherent problems.

Here are a few pics of what I've been doing in that respect:

I have been able to pick up a pair of used 2500 gph units, One with a bad motor, and the other was leaking between pump and motor. I took the cartridge canisters from both, and using 1-1/2" PVC pipe and fittings, plumbed them in parallel. Using the good pump from one of them, I've come up with this:

http://i1094.photobucket.com/albums/...ps1a85a189.jpg

I've given myself a spot for a third canister, if I can find one. Even with two, the filtration difference is noticeable. I do use Unicel cartridges in them (C-5315) giving me 30 sq ft of filter area. Still not as much as it should be by the 1:100 rule, but getting closer. Note: I do keep my pool a little fuller than Intex intended, so it calculates out to 4800 gal.

These canisters are easy to remove from the base, just a couple of clips on the transfer tube, and a large nut on the bottom of the canister.

I've also been hard plumbing my pool. I started with the returns, adding two using Hayward vinyl liner fittings with the 1-1/2" internal threads.

http://i1094.photobucket.com/albums/...ps227d30e1.jpg

http://i1094.photobucket.com/albums/...ps37c038db.jpg

http://i1094.photobucket.com/albums/...ps6cc65047.jpg

Doing this has given better water circulation in the pool, and definitely helps with keeping it clean and clear.

Yes, I used an electrician friend's trick and warmed the PVC pipe to bend it around the pool, allowing for less connections so lower potential for breakage/leakage. PVC will flex some in this situation, so should give a few good years of use.

I am also planning on installing a Hayward SP1091LX or similar through the wall skimmer, and a low suction port next year, to complete the hard plumbing.

I may try a cheap 1 hp pump, given that the Intex pumps aren't known for being very efficient.

Let me know if you have any questions on how I've done any of this.

Charlie_R, thank you for taking the time to post this -- very cool! I had been wondering about using defunct units as filter housings; interesting to see that you have had success with this approach.

One question, regarding multiple return points -- does that mean you had to cut additional opening(s) in the pool liner? If so, no problems with doing that in a non-reinforced spot on the pool wall?

Since we happen to have a donut pool (LOTS of wall movement with swimmers in the water) we wouldn't be able to do hard plumbing all the way up to the pool... but your setup gives a lot of food for thought. Thanks again for posting the description and photos.

Yes, I cut new holes in the pool liner. No I didn't add any reinforcement. Another forum I frequent has many people hard plumbing their Intex regular and ultra frame pools, with no reported problems. One of the main advantages of hard plumbing is the ability to upgrade to normal above ground pool pumps and filters.

If you are worried about it needing reinforcement, find someone who is replacing their pool or liner, and see if you can get either the whole liner or just part of it. You can use this to reinforce the areas you want to add intakes or returns. With yours being a donut, it would be a good idea. If you upgrade to either the regular frame or ultra frame, you could hard plumb. Actually, there is a flexible PVC available, that would handle the movement between the intake/returns, and hard PVC. Unfortunately it does get a bit pricey.

I don't know if you noticed in the pics, I've done a partial bury of the pool. If I'd have had more energy and less pain, I would have gone at least a foot deeper. This has had the effect of stabilizing the pool, even with it only buried to the band. I've had guests with kids in the pool, jumping off the ladder platform. Very little wall movement. Note that Intex doesn't like the idea, probably due to the potential of the legs rusting off below ground level. The pool liner itself will handle the dirt being up against it, no problems. I'll handle the leg problem if/when it happens.