DE vs SAND Filters

[joe123]

Hi.

I need to replace 20+ year old 60 Sqf Sand Filter and was wondering which to replace it with? Another Sand Filter or a DE Filter?

I have 2 inch pvc pipes, a Pentair 1.5 HP WhiserFlo, 400k BTU gas heater, 60 sqf Sand filter, large pool (not sure size) and spa.

In my previous home, I had a DE filter and it worked great. On my existing home, it's a Sand filter.

The filter I am looking at is the Pentair DE FNS 60 sqf filter. Any reasons to go with a DE vs a Sand Filter?

If this subject has been beaten to death already, please point me to the linkies.

Thanks a bunch,
Joe

 

[JasonLion]

There is no one true answer. Each system has it's adherents. Sand is a bit easier to maintain, DE filters a bit better. It really comes down to which system you feel more comfortable with. In either case getting a filter that is larger than what you need will help significantly.

 

[joe123]

Ok thanks and I agree 100% on over-sizing it.

Question on flow rate. Looking at the Pentair DE / Sand Filter flow rate for the same size filter, I see:

120 GPM - Pentair DE FNS Plus 60 Sqf
63 GPM - Pentair Triton II (TR60) Sand Filter 60 Sqf

I am not sure what the flow rate is on my current Sand filter, but it looks about the size of the Triton II (TR60).

If my old filter flow rate is around 60-80 GPM and I go with the Pentair DE FNS 120 GPM, would that not be consider a "larger" filter? I am not sure how to compare DE vs Sand filter to determine capacity.

Joe

 

[JasonLion]

You want to compare flow rates. If you can afford it, look for something that is at least double what you estimate the flow rate is for your system. For DE filters, look at the optimal flow rate, not the max flow rate. A 1.5 HP WhisperFlo can easily move 60 to 80 GPM, depending on the rest of your system, so I would be looking at filters much larger than the two you listed, or possibly look into getting a smaller pump. A smaller pump can easily pay for it's self in saved electricity, assuming you don't need the large pump for some reason (your pool is really huge or there is a spa or waterfall.

A typical sand filter is 1 to 8 square feet. The TR60 is actually 3.14 sf. Sand and DE filters work very differently, so you can't compare square feet directly. External dimensions are generally about the same for similar flow rates.

 

[joe123]

I would be looking at filters much larger than the two you listed, or possibly look into getting a smaller pump.

Ok, I lost you there.

When you say "much larger" than the Pentair FNS DE 120GPM, what are you suggesting, a 200GPM DE filter? Do they make those?

My limited understanding is that my current Sand Filter is similar to the TR60 which is rated at 63GPM. I thought going to a Pentair DE FNS filter at 120GPM would be a nice over size filter (2x size of previous filter), but you are saying that is not big enough?

I know that it varies a lot (lenght, turns, etc), but I thought 2 inch PVC pipes normally handles around ~150 GPM max.

What kinds of filters are you suggesting I get and of what GPM size?

Also, I recently replaced my old 2HP motor with a Pentair 1.5HP which was the right choice (.5HP less) in that my water flow is very strong and just a tad faster than with my old motor.

 

[JasonLion]

The Pentair FNSP60, which is the model I believe you are referring to, has an ideal flow rate of 60 GPM and roughly corresponds in size to the TR60. The 120 GPM peak flow rate is not the one you want to be looking at. Both of these filters are marginal for the pump you have, they *will* work but the flow rate is higher than you would really like to run them at. You only need to go a little larger, to 80 GPM ideal flow rate, to match the spec on your pump. I would go much larger than that to reduce how often you need to backwash the filter and to improve the efficiency of the entire system.

They do make larger filters, for example the Pentair Quad D.E. 100, which is designed for 100 GPM (or 160 GPM using the column that corresponds to the 120 GPM figure you were quoting earlier). In sand filters you could look at the TR100 or TR140.

2" pipe can actually run way above 150 GPM, but the system efficiency starts to fall dramatically when you do that. However, that is not what I am talking about. I am suggesting getting a filter rated for twice your actual flow rate but running it at the lower rate. The higher flow rates won't actually occur in your system. They do make very large filters, larger than the Quad D.E. 100, for commercial pools. With a large residential pool it is sometimes worth looking into such filters. You never said just how large your pool is. If it is larger than 30,000 gallons you might well want to look at commercial filters larger than the Quad D.E. 100.

If you switched to a 3/4 HP pump, or got a two speed 1.5 HP motor and ran it on low speed, you would need to run the pump twice as long but you would use just a little more than half as much electricity total. The lower flow rate would also allow the filter to filter more effectively. There are cases where you need a 1.5 HP pump, if you have a spa or a waterfall for example. You would also need a 1.5 HP pump if your pool has say 50,000 gallons. If your pool is under 28,000 gallons and you don't have a spa or waterfall or anything similar, a 3/4 HP pump would save a dramatic amount on electricity costs and filter the water just as well or better.

 

[joe123]

Thanks Jason.

I was confusing the GPM readings. Also, thanks for the info on the Pentair WhisperFlo 1.5HP moving 60-80 GPM, I looked and looked and could not find that info on the web.

So it looks like the Pentair Quad 100 (maybe Quad 80) filter will work for my pool. I think the size of my pool is in the 30-40,000 size. I do have a spa, so I need to keep my 1.5 HP motor for the yets 8)

One last question on the Pentair Quad Filters please. According to the Pentair Quad Filters specs, is shows the GPM flow rate and turn over capacity for the 80 and 100 Quad units to be the same. So does this mean that the GPM flow rate is the same on both of these filters? So the only advantage of going with the 100 instead of the 80 is the less frequent backwashes and not any better GPM efficiency?

 

[Titanium]

joe123,

I know that you wanted to concentrate on sand or DE filters, but have you considered a cartridge filter? I have a 400 square foot cartridge filter that I only have to clean once or twice a year. And there is no wasted water due to back flushing. Although I have to admit that there is a fair amound of water used during the cleaning process.

Also, it would be great if you listed your pool specifics in your "signature" line. Here is a link on what kind of information should go in your signature - http://www.troublefreepool.com/viewtopic.php?t=52

Titanium

 

[JasonLion]

The data I have seen on the Quad DE 80 and 100 shows ideal flow rates of 80 and 100 GPM respectively with a maximum safe flow rate of 160 GPM for both. The Quad DE 100 has 25% more filter surface area so it will have less resistance to flow and go longer between backwashes. The data sheet you link to doesn't show the ideal flow rate, which is listed on this page at their web site.

 

[joe123]

joe123,

I know that you wanted to concentrate on sand or DE filters, but have you considered a cartridge filter?

Titanium

Hi.

I want to stick with DE or Sand. I asked several people and everyone has a different opinion about DE or Sand. The only thing that they all agreed on was to stay away from cartridge disposable filters.

I like the Pentair Quad which has cartridge filters, but they are not the dispossible type and it uses DE. These I like.

 

[Exchemist]

Well, just to confuse the situation, I would go with a cartridge filter.

I have a DE filter and find that while it filters well, it is a pain. Handling and disposing of the DE should be done with care -- it is a carcinogen. Also, the filter must be disassembled and washed out once or twice a year to remove accumulated DE. The people I know who have sand filters have just as many, but different problems. Everyone I know with a cartridge filter has few complaints.

 

[lovingHDTV]

I've had a sand filter for about 5 years and besides replacing the media with Zeo<something> I backwash once a month and have no other issues.

One neighbor has DE and I hear him cussing it all the time, another neighbor has catridge. I've not asked him how he likes cartridges, I'll ask him.

When I had cartridges for my hot tub I hated them. I could not clean them without getting dirty and all wet. Maybe I was just doing it incorrectly. I remember soaking them in big buckets overnight, is that still needed?

my $0.02

 

[joe123]

I've had a sand filter for about 5 years and besides replacing the media with Zeo<something> I backwash once a month and have no other issues.

My first pool had a DE filter. My second home which I am at now has a Sand Filter - some 10 years with it. I love the Sand Filters but everyone - and I do mean EVERYONE that I have asked in person says to go with a DE filter and not Sand. I don't know why?

I will say that my Sand filter does *not* filter as good as my DE filter did in my previous house. You are one of the few who has said Sand is better.

Has anyone done a Polling of this here? Sand or DE - which is better Overall?

 

[JasonLion]

There is no one best kind of filter. Different situations and personal preference will make different kinds of filters better for different people.

Sand
Pros: The simplest to operate, just backwash occasionally. No ongoing expenses except water.
Cons: Lets the largest particles through.

DE
Pros: Filters out smaller particles than any other filter.
Cons: Can require very frequent backwashing if you have algae. Backwashing is more complex than sand.

Cartridge
Pros: No backwashing, the best choice if you have expensive water or water restrictions.
Cons: Cartridges wear out eventually and can be expensive to replace. Some people don't like cleaning cartridges which can be messy.

I add a little DE to my sand filter to get filtering nearly as good as a DE filter without the (minor) hassles of a regular DE filter. Others love cartridges. If you get a large enough cartridge filter you may only need to clean it once a year. On the other hand, you can't beat a DE filter for water clarity. A little of this, a little of that, pick the flavor that you like best.

In all cases getting a filter that is larger than what your system requires will make everything simpler and more efficient.

 

[Butterfly]

Hey joe123,

The only filter we know anything about is the one that we have: SAND! It is easy to operate and we love it. Our pool stays pretty clean......and as for any large particles getting through?? ...don't know about that :? ...well, maybe the skimmer sock we constantly use helps keep the water so clean. Anyway, fwiw, if we should need to replace (circa 1992), we will stay with the SAND!

I think there was a polling of sorts on the filter choice this summer. Maybe somebody can drag it up for you!

Good luck with your decision!


Joyce

 

[SeanB]

I think the difference in water clarity between the three is so minimal, that it is a non-issue for most users.

The important factors are ease of use and cost.

We are in a MUD district and there would have been issues using sand or DE so went with cartridge. I have to say, I've been very pleased. In the past year, I've cleaned my cartridges twice - both times before we actually reached the recommended pressure, so they could have gone even longer. I believe 3-4 times per year is typical.

Cleaning is about a half hour process. You have to remove the lid, pull out the cartridges (4 in my case) and wash them individually between the pleats, using a pressure tip water hose. I think the life of the filters will be around 3 years. If you use lots of suntan oil or other greasy products that come off in the water, then you may have to soak the filters overnight in a degreasing solution. Our kids always use water-proof sunscreen and the wife and I don't put on oils, so it has not been an issue for us.

This is an often discussed topic and would make a great article for the newsletter. If anyone would care to write one, send me a pm - you would, of course, be given full credit. It would need to cover the basic operation of each type, pros and cons, maintenance and life expectancy and any other inoformation you think people would find usefull.

 

[PoolGuyNJ]

I care for a lot of pools in NJ. A pool of your size needs either a 30" diameter/500LB sand filter or a 60 Sq.-Ft. DE filter. Both will work well.

The sand filter will be easier to maintain, will take up a little more equipment pad area to install. It's media (the sand) normally needs to be changed about every 5 years. Backwashing procedures are similar to most DE filters.

DE filters, in addition to backwashing and recharging with new DE, need the grids removed and hosed down every couple months. Sometimes they need degreasing too (usually in a clean garbage can). They usually take up a smaller footprint at the equipment pad than a large sand filter.

Water clarity, as far as a person's eyes can tell is the same though a DE filter, when new can filter a smaller particle. Neglecting proper maintainence that will change that.

Repair costs are usually higher with DE filters.

What do I have on my pool? A sand filter. What will I replace it with? A sand filter because I hate dealing with DE and I don't want to be bothered with caring for a DE filter when I come home.

If I built a 40,000+ gallon pool for myself, I would probably go DE to help keep the equipment pad smaller.

 

[JasonLion]

If you use the BBB method of pool care and pay a reasonable amount of attention to your chemical levels it is very uncommon to need to disassemble and clean a DE filter or replace the sand nearly as often as you suggest. The principals are the same, both things need to happen occasionally, it is just that by avoiding putting things you don't need into the pool the filter will typically be able to go longer between cleanings.

I can see what to me is an obvious difference in the appearance of the water between sand and DE filters. Some people don't notice the difference, others do. In both cases the water is crystal clear and transparent (assuming everything is working correctly).

 

[carlos31]

maybe you should check clearpro

Pentair claims their new "clearpro" technology provides near DE performance with the ease of sand. I guess the first person on the forum to own one will need to tell us. You can read about it on their website under "what's new".

 

[Guest]

I'm gonna have to side with NJ pool guy. DE filters NEED to be broken down on a regular basis. In fact I will go as far as to say that backwashing them is not a good idea at all. When you backwash you never really know how much DE you remove so you never really know how much to put back in. The first time you have to break down a DE and chip away the hardened DE powder from between the grids of an overcharged filter you will understand what I mean! Also, backwashing forces dirty water BACKWARDS through the grids. We are always cautioned about running a DE filter without DE in it so we don't foul the grids but isn't that what we are doing every time we backwash one? Once again a good case for soaking the grids once or twice a year.

As far as sand goes, the filtering is done by the sharp edges of the granules which trap the dirt between them. As the water flows over the sand these edges get 'polished' and rounded off and the filtering ability is lessened. New sand filters better than old sand! Ask any aquarist who has ever used a sand filter! (I'm talking mechanical filtering here, not biological which is not applicable to pools.) Pools are no different. In fact some of the filters are identical! (For exanple, Pentair makes sand filters for large aquariums and ponds as well as pools. Funny thing is they are exactly the same!)

Sand does also need a more thorough cleaning than backwashing alone can do perhaps once a year. I recommend opening up the filter, sticking a garden hose in the sand and turning it on. Let the water flush out all the crud that has collected in the sand until the overflow is clean. You might have to CAREFULLY break up the sand with something like a broom handle if it is clumped together! (I said CAREFULLY so you don't damage the laterals!) If there is evidence of scale buildup then an acidic sand cleaner might be in order!

Don't get me started on Zeolite filter medium as a replacement for sand! Let's just call it snake oil and be done with it. (If anyone insists I can dig up the posts I made about it on some other forums and repost them here).

Now as to the GREAT DEBATE of which is better bottom line is this, most people are very happy with the type of filter they get once they get used to maintaining it. Each type has it's own set of tricks to get the most out of it.

Sand is by fart the easiest to maintain and probably the least maintenance but it's filtering ability is the lowest. This can be particularly evident if your pool is lighted at night. Filter aids such as DE powder or cellulose fiber can help improve sand's filtering ability. The constant backwashing will tend to throw your water balance off but it is useful if you use trichlor or cal hypo.

Next comes Cartridge filters. You either love them or hate them....there seems to be no middle ground here. Personally I love them. No backwashing so your water balance tends to stay put (a plus with a SWG, a minus if you use trichlor!). Their filtering ability approaches DE in particle size filtered out. Carts do wear out and need to be replaced every few years. For very big pools they are not practical since you will be stuck with one of those 4 cart monsters that are a real pain to clean! However, some townships have outlawed sand and DE filters so carts are the only choice. Proper cleaning is not hard but it can be a bit messy. Wear your swimsuit so if you get a bit wet it's no big deal.

Finally DE. No question, these really polish the water but is the work involved worth it for you? That is what you have to ask yourself. If you do a lot of night swimming in a lighted pool you might want to invest in one since this is where the difference in water clarity really can show up.
Now there are 2 basic kinds of DE filters, the bump and the backwash. Theory behind the bump type is that when the filter gets dirty you 'bump' the dirty DE off the grids so it can mix with the dirt and then recoat the grids with dirty DE! (I must confess I never quite understood the logic behind that--dirty DE is dirty DE!)

The second type can be backwashed but I've already said what I think of backwashing a DE filter. IMHO, ANY DE filter should really be broken down for cleaning!

Bottom line is this, any filter type you choose is going be a compromise between filtering ability, ease of maintenance, and real estate taken up on your equipment pad. Just research your options and make a decision on what you think will fit best into your lifestyle! I don't think you will regret your decision no matter which filter you choose!

Be aware that some townships require a DE separation tank for backwashing DE filters. This can add to both the expense and the space they take up on your equipment pad.