Is a sand filter better for using with biguanide than a DE filter?

MITBeta

Well-known member
But wouldn't the algae be visible - as in green, yellow, etc.? There is no trace of anything like that - at least that can be seen. I moreso suspect the WWM (fungus).
No, not necessarily. As I found, a constant, low level amount might double in size during the day and have half of it killed off overnight. Level is too low to be visible, but dead algae appears on the pool floor every almost daily. It could be mistaken for dirt or something else.
 
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anthonypool89

Well-known member
Aug 26, 2016
423
Berks County, PA
Well, they WILL drain, but it takes an hour or more. You can grab the bottom of each grid and the water just sloshes around inside. Needless to say, this makes them a bear to try and lift out of the tank since they're probably like 10 times heavier than they should be. These are my original 31-year old grids, so perhaps just shot? I do have trouble with them turning - had the whole thing apart a few weeks ago (FUN!!!!...sort of like working with huge white dominoes to get the thing all back together again). On the end one, it seems the grid material does not stay under the round plastic piece - but I figure - water passes THROUGH these things constantly, so why don't they drain?
 

WilliamD

Bronze Supporter
Jun 23, 2020
35
Leicester, MA
Anthony...I don't know what brand or model of DE Filter you are using so I can only relate to my Hayward EC 50....If I had that problem, I would inspect the grids to make sure they are not clogged (Which seems to be the case) and clean them appropriately. As far as water getting into the grids when clogged...I would check for mis-aligned grids and ensure all the screws that attach from the manifold to the bottom plate are secure. Water could be coming in from the top of the grids and not actually passing through the grids because they are clogged so the water doesn't drain. Also look for any small holes or tears towards the top of the grids as well.....Hope that helps.
 

anthonypool89

Well-known member
Aug 26, 2016
423
Berks County, PA
Right now they are in a bucket of filter cleaner, but they had been cleaned the end of last season and did the same thing when I used them at the start of this season. As I said, I had them all apart. They may just be clogged to the point of no longer really being effective. There really are no individual screws - just one long bar that passes through the middle of all 10 grids and then a bolt on one end and an allen screw on the opposite end. Here is what I have: Val-Pak Products Grid Assembly 52-2 Apollo Complete 2in. If you loosen both ends, the thing falls apart like and each grid can be removed - not the easiest thing to get back together - takes two people to do it.
 

anthonypool89

Well-known member
Aug 26, 2016
423
Berks County, PA
Correct me if I'm in error on some of these observations: I'm told that DE is the best and finest filtration; however, it's because of this that DE with biguanide causes filter coagulation (and frequent cleanings) since the biguanide molecule cannot pass through it whereas with sand (not as fine filtration relative to size of particles it allows), the biguanide passes through - thereby creating less of an issue. One option I've been considering - as a result of my problems with biguanide (well known here 🤪), IS to go with a sand filter - but is the water going to be as clear? In general, IS sand as good as DE? What is the recommendation on this?

Let me go one step further - of these two options - which is the most preferable one: 1) stay with DE and convert to chlorine 2) stay with Baquacil and get rid of my DE filter (would sort of hate to do that - the thing is a proven workhorse for 31 years!!) and substitute for a sand filter???

Thoughts?? How good is the water quality with sand?
 

Msch99

Gold Supporter
Bronze Supporter
Jun 11, 2018
828
Verona, MO
We have a sand filter and our pool is partially under a tree. I have added a cup of DE to increase filtration when opening the pool, so that is always an option. But having said that, we don't have any issues keeping it clear.
(Clear referring to floaties in suspension, not clear referring to algae)
Pick a side on sand or cartridge...I can argue which is best either way! :laughblue:
 

anthonypool89

Well-known member
Aug 26, 2016
423
Berks County, PA
The pool store I've dealt with always has told me that sand is better with bigaunide because of what I mentioned in the initial post; however, they also jus told me that THEIR sand filters as fine as DE. If that's the case, I'd probably wind up with the same results if the sand doesn't allow the biguanide to pass through. This is all speculation and heresy of course.
 

anthonypool89

Well-known member
Aug 26, 2016
423
Berks County, PA
Maybe the better question might be..."should you use a flocculant" if you can't vacuum the waste? I imagine you could still use it but might need to backwash and/or take the filter apart several times. (I've been doing this anyway nearly every week since I opened the pool).