the truth on DE filters

[PanamEric]

Hello All...

I am looking for sound advice and after spending hours and hours looking at various vendors web sites I decided to check TFP...hoping someone can shed some light on the topic.

I live in a tropical paradise...but every place has its inconvenients.
The temperature is nice (high 80s) all year round and we have two seasons. Dry season and rain season. For half the year we've got plenty of water but the other half it can get quite scarce to a point where doing a backwash is a big no-no . IN fact with the heat and lack of rain it is sometimes a challenge to keep a pool above the skimmer line.
If you happen to need to do a backwash at this point you are kind of screwed because you have no water to bring the level back up. This kind of stinks because the dry season (summer) is when you need the pool the most.
So I came across DE filters and retention tanks that from what I am reading allow to send the backwash water back to the pool...Perfect! That's what I need...So i started looking and after dozens and dozens of different web sites all claiming to have the best I admit I am more confused than anything else.
It sounds too good to be true...and when it does it usually is because it is too good to be true. So where's the catch?
can you really send the backwash water back into the pool if you are using a retention tank?
Also I read that perlite seems to be a better medium than DE because it is easily backwashable...? So does not need to be changed (or topped off) at every backwash.
So I am looking hopefully for someone whom can give me the ugly, naked truth on DE filters, retention tanks and perlite instead of DE as a medium...

Does it make sense? Is it really possible to re-use the backwash water with a retention tank? Does it make sense to use perlite instead of DE...and if doing so will the retention tank work the same way? Is it really possible to backwash perlite medium?
I find the info on manufacturer sites is very basic at best and somewhat biaised ...vendors are even worst in terms of information, so I am not sure I can fully rely on any of them but I do have faith in TFP members...
Thanks for any input
Eric

 

[Ohm_Boy]

You sure you wouldn't just like to have a nice, big cartridge filter? No backwashing, no retention tank, no topping off, just clean, clear, filtered water.

 

[PanamEric]

Hello Ohm_Boy,

Thanks for the input. I must admit I am not at all familiar with cartridge filters and always thought they were only for kiddy pools.
I have had one of these (for kiddy pools) and did not find it to be too performant and the cartridges needed to be changed real often as they were not really cleanable.

I am assuming that this is different on larger size but surely you have to change the cartridge at some point...
How well can you wash them? You wash with a hose? How long do they last?
My concern is getting a supply of cartridges here (and their greatly boosted cost).
Thanks
Eric

 

[257WbyMag]

I clean my cartridges once or twice a year. A set of cartridges will last years if treated right. They are cleaned by spraying them off with a hose.

Kiddie pool cartridges are not the same as regular filter cartridges. Two totally different things.

 

[Melt In The Sun]

My carts are 5 years old now, and are working well so far. The rule of thumb is 5-10 years of life.

You say you have no water to bring the level back up? Do you mean there's no tap water available at all? If that's the case, you wouldn't really have a way to clean cartridges when they got dirty. I hope I'm misunderstanding you...?

 

[PoolGuyNJ]

Recovery tanks usually have a heavy fabric bag that captures the spent DE and send the water back to the returns. When the back wash and rinse are finished, the tank bag is emptied. They usually work quite well.

Scott

 

[mas985]

I clean my cartridges once or twice a year. A set of cartridges will last years if treated right. They are cleaned by spraying them off with a hose.

Kiddie pool cartridges are not the same as regular filter cartridges. Two totally different things.

+1


If I had to do it all over again, I would probably still choose a cartridge.

 

[PanamEric]

My carts are 5 years old now, and are working well so far. The rule of thumb is 5-10 years of life.

You say you have no water to bring the level back up? Do you mean there's no tap water available at all? If that's the case, you wouldn't really have a way to clean cartridges when they got dirty. I hope I'm misunderstanding you...?

Thank you MITS,
I don't have city water. Some years are drier than others. I do have two wells but In those drier periods they get low and water becomes a very precious commodity. Ironically that is when we usually need the pool the most. Also collect rain water from all roofs but we nevertheless have to use the water diligently.Now guessing that I would have to get a fairly large one to match my app 120gpm flow (would like to keep same pump ) at what frequency would they normally have to be cleaned? Assuming little organic contamination, since I got no trees dumping leaves around it and as stated little rain to carry atmospheric dust in? I am not expecting a precise answer here...just an indication. I think I would probably be ok if I used a
pressure washer since they use little water and I assume the cleaning should only require a few minutes...providing of course that they don't have to be cleaned every other day!

To give you an idea, in summer the garden is being watered with a timer and individual mister for each plant. However things should be a bit better this year with the 10,000g tank I just finished.
Are there any suggestions on sizes and brand that outperfom others or have cheaper replacement parts or is it like sand, pretty comparable for one to the next?
Thanks for any input
Eric

 

[acroy]

Honestly I'd suggest do a backwash right at the end of the rainy season while you still have lots of water - then just let it go. Even if pressure goes a few psi over the rule-of-thumb 10psi increase, you'll be ok. You stated you have little load on the system during the dry season, no trees and no rain washing dirt into the pool, so I bet you'll be fine. I get 6-8mo out of a single charge of DE on my filter, and I DO have lots of trees etc

By the way, your signature says 600lbs sand filter, not DE... which do you have?

 

[Ohm_Boy]

I've known several folks with cartridge filters that need to be cleaned about once a year. The filtration can be pretty close to DE in quality, but cartridges may need to be replaced after ~5 years. They can get kinda pricey.

 

[257WbyMag]

Yes, the cartridge filters can get close to DE in filtration. I cannot remember the numbers but measured in microns, the DE filters down really small. However, I have a couple of friends who have DE filters. Some would say that the DE filter maintenance is a little more work than cart filter maintenance is and I can sort of see that. Had I the opportunity to do it over again, I think that I would still go with the cart filter.

Regardless of the filter that you choose, get a bigger filter than you think you need. This is always a good thing.

 

[PanamEric]

Thank you all for the input...
A bit weird I replied 2 hrs ago (with Quick reply) and my reply does not show here??

In any case in reply to Acroy. I do have a 600lbs sand filter as my signature says but because of reasons cited above I am/was considering switching to DE (with retention) and thinking of using perlite as a medium instead of DE. Anybody whom has input on perlite medium that would be great.
However I am now also looking at cartridge filters as well thanks to various inputs received here.
So basically looking at ways to recycle backwash water or eliminate the backwash cycle.

I have to look at this carefully as eventhough most things are ridiculously cheap here, swimming pool stuff is just the opposite, like 3 to 4 times the prices from back home. This is due of course to the relatively small percentage of swimming pool owners...and accordingly only a few retailers to service them and they really lay it on thick. Granted most pool owners are filthy rich but that's not my case, I still need to be careful how I spend my $...they are a lot harder to earn than they are to spend.

DE as an exception is fairly cheap (make that somewhat affordable) and readily available... Granular Chlorine is $3/lb unless you buy it wholesale. All parts and other things I bring in from the US. However cartridges I would assume are bulky so would make for expensive shipping...but don't seem to need replacing that often...
I am concerned with the impact of dumping DE which is why I am looking also at a DE canister with retention with perlite medium, which is somewhat permanent... :?:
I think cartridge and DE use the same canister? Am i right?
So with DE (or perlite) I would also have the extra expense of the retention tank.
Also in reply to Acroy I don't have any real contamination from leaves and only little rain (in the summer) but I do have a somewhat increased bather load...

Is my reasoning sounding right so far?
Any first hand experience with perlite would be great. I find it interesting but am curious to read real life experiences.
Thanks all
Eric

 

[chem geek]

Yes, the cartridge filters can get close to DE in filtration. I cannot remember the numbers but measured in microns, the DE filters down really small. However, I have a couple of friends who have DE filters.

It varies a lot by specific product, but generally speaking sand is in the 20-40 micron range when dirty (50-60 when not), cartridge in the 10-15 micron range for higher quality cartridges (20-25 micron for less expensive cartridges), and DE in the 3-6 micron range.

 

[Guest]

I spoke to my local Pentair rep; 4 microns on the Clean & Clear plus cartridge filters!

Almost 9 years on my cart's now. I clean them every 6 months, if they need it or not. Still like new. I've been doing this line of work for right at 15 years now and have never seen anyone replace a cartridge (StaRite, mostly, in my case) yet.

 

[Melt In The Sun]

I think geekgranny uses perlite...haven't seen her around in a while. You could send her a PM and see what her experience is.

 

[chem geek]

I spoke to my local Pentair rep; 4 microns on the Clean & Clear plus cartridge filters!

This brochure says that the Pentair Clear & Clear® Plus filters down to 30 microns. I don't think your Pentair rep is correct.

I have a Jandy CL340 cartridge (4-cart) filter that I clean once a year. I did replace the cartridges at the start of this year after 6 years. I could have probably gone longer, but the straps were not holding the pleats well anymore and I just thought it was time. Usual quotes for cartridge filter elements is that they last 5-10 years.

 

[Guest]

I have that brochure, and I had called to specifically ask about the 420 (which is listed on the brochure). We are considering moving away from the large sand filter in our trailer on future trailer builds to a cartridge filter, and I needed a comparison. The sand filter is large and heavy, and we would like to lose some weight, but not compromise that portion of the filtration in the system (although the R/O membranes are doing the majority of the work and this filter is more for "pre-treatment").

I'm going to call the Rep again to clarify. Thanks Richard; I don't want to spew false information, and we definitely have a conflict of information here!

 

[PanamEric]

Thanks Chemgeek,

Your post was just on time...I was just finishing to check the best deal I could find on a Pentair and was prepared to order it...only had 3 or 4 more vendors to check.

The 4 microns argument had won me over... cartridge with same as DE mechanical filtration, no backwash, no retention tank...what's there to think about? I was actually wondering why this was not the only type of filter in use.

I know you are a strong proponent of proper chemical treatment but I think that with improved mechanical filtration the battle would be easier to win? Would it not?
For the sake of argument and better understanding filtration vs chemical treatment...let's say one could effectively filter to super small size, say 1/10th of a micron, how would it affect the need for chlorine (or other oxydants)? Just thinking out loud...
Thanks again...you saved me from a "stupid day".
Eric

 

[chem geek]

Different manufacturers make different claims and except for DE which has a specific test as part of NSF Standard 50 that is quite stringent for water clarity, the other filter types (sand and cartridge) do not have a tight standard to meet. They do have a standard, but it's loose and the same for sand and cartridge. Hayward says that sand filters to 20-40 microns, cartridge to 10-15 microns and DE to 2-5 microns. The only consistency is with DE where pretty much everyone is somewhere in the 2-6 range.

It's very likely to be bogus marketing for a cartridge filter claiming to filter to 4 microns. It's not that there aren't microfiltration cartridge filters, but they are more expensive and are used in lower flow rate conditions such as drinking water filtration. There is also The Slime Bag but you will note that only a portion of the water goes through the bag on every turnover in residential pools. It's not impossible to get fine filtration out of a cartridge filter, but it would require a different design with very high surface area in order to allow for reasonable flow rates without extraordinary pressure (head).

As for filtration vs. chemical treatment, both are important, of course, but filtration is mostly about water clarity (whereas circulation is about even distribution of chemicals including chlorine and also about skimming action to remove surface debris). Micro or ultra filtration would be great for removing Cryptosporidium and other protozoan oocysts that chlorine has difficulty in inactivating. It would also be good at removing some organic precursors in fine particles such as dead skin, pollen, etc. though most filters do a decent job with this, but would need to be backwashed/cleaned to remove them from the water flow (otherwise chlorine demand is still high oxidizing such material in the filter). So for commercial/public pools, such filtration is more useful, but for residential pools it's overkill except for water appearance with DE. Most chlorine demand in outdoor residential pools is from breakdown of chlorine in sunlight; relatively little comes from bather load or other organics in the pool unless one gets a lot of debris (including pollen).

 

[Ranger987]

I've heard the various sales reps use the 4-5 micron number for cartridge, but it's related to "loaded" cartridges, which have a coating of debris which helps filter out smaller particles. Clean filters obviously don't do that. When customers ask me about the lifespan of a particular product, I try not to be specific. I'm told that many products are designed with an 8 year life expectancy, although most get much better than that, some less - depending on maintenance. In my my experience, the difference in quality of filtration between DE and Cartridge isn't visible, chemistry & runtime being equal. I've seen suspended particulate in DE filter pools (nighttime with the light on) after 10 hours of runtime too. The type of pool cleaner has a lot to do with the suspended particulate, as a "bag-type) cleaner will put particles back into suspension even though the pool looks clean.