Filter Types

[rweccleston]

Bought house in January with 20 year old IG 20 by 40 rectangular pool. Had been closed for 6 - 8 years and was a swamp when we opened it (mud, snails, tadpoles, swamp grass, opaque green color). Fun!!
Pool clean now, want to replace sand filter which appears to be original equipment. Pinhole leaks in housing that pump bolts to, multiport valve leaks, and so on.

Reading about Sand vs DE vs Cartridge, I get the impression that a sand filter is inadequate in that it won't filter out algae, which seems to be the most common contaminant.
DE will remove algae (down to approx. 5 microns or smaller).
Cartridge will remove the algae and anything else that gets in because it filters down to bacteria size.

I am leaning toward a DE filter (easier to clean than Cartridge, IMO) combined with a robotic pool cleaner.

Any better suggestions?

Thank you!

 

[mknauss]

Welcome to the forum! :handshake:

A filter is not designed to nor should be expected to filter out algae. Algae is a chemistry problem, not a filtering problem.

Sand filters are the simplest and are great in areas that fill water is not an issue (no iron, cheap to obtain, etc). DE is great at filtering but take more effort as they need to cleaned thoroughly at least once per year. Also the effluent during backwash has DE in it that can be an issue. Cartridge is great for areas that water is not cheap, for SWCG pools such that you are not having to add salt due to backwash, etc.

Pool School - Pool Filter Comparison

The most important thing is to get the largest filter you can fit on your equipment pad and can afford. Bigger means cleaning less often.

If you are interested in learning more about TFPC, I suggest you read Pool School - ABCs of Pool Water Chemistry and consider reviewing the entire Trouble Free Pool School book.

 

[Donldson]

Welcome to TFP!

Just to throw some personal experience in, I switched from a cartridge filter to sand filter when the cartridge housing on my filter started to degrade. My water has been clearer since the change. Now sand filters don't filter as finely as cartridges, so how is this possible?

Well, the most important thing to clear water is proper chemistry. That is not the same thing as a pool store saying that your water levels are fine, as you will find out reading here. So there is virtually no algae in the pool to be filtered out to begin with. Next, the cartridge was somewhat undersized for the pool and I will sheepishly admit to not cleaning it as often as was probably required. The sand filter is well oversized for my pool and with the ease of backwashing I am more on top of doing it as soon as needed.

I'm not trying to dissuade you from a DE filter or any other type, they all work great when properly sized and paired with a properly sanitized pool. I just want to make sure you are picking one for the right reasons and understand what is a chemistry issue and what is a filtration issue.

 

[rweccleston]

Thank you both for your responses.
I completely agree with everything you said.

I have to admit that I am still favoring a DE filter after cleaning up the swamp I encountered. The algae had to be pumped out of the pool wasting thousands of gallons of water. The sand filter just recycled it back into the pool.

Going forward, the DE filter should remove any algae blooms that occur if the chlorine levels drop for any reason. As you stated, algae is a chemical issue, until it blooms, then it's necessary to filter out the dead algae.

Since the old sand filter container is not damaged, I might keep it (new sand), put in a DE filter, and set it up so that I can switch between the two. Has anyone else ever done that?

I plan on replacing the filter in the spring when I reopen the pool, so I have lots of time to think on it.

 

[MrGreg]

As a long time pool owner, I would lean very hard towards a DE filter. Mine is a Hayward "Perflex" bump style filter. I am not sure what you meant by a DE not filtering out larger material. As mentioned above, anything larger than 3 micron. That includes dirt and sand. DE powder is the consistency of talcum powder. Once your pool is clean you will not be bumping, or recharging, the filter often at all.
I am not familiar with the "backwash" type DE filters but it would be a pain to replace half my powder every time I backwashed.
After the bumping process, (simply raising and pushing down hard on the handle 3 times or so) you simply start your pump up. A small poof of DE powder will be noticed, but that has never been an issue.
My system involves a sand filter+DE filter. I use the sand filter only when vacuuming. It picks up larger debris(bugs, leaves, etc.) The DE filter then gets all the very fine matter. I have it valved so I can bypass the sand filter back to DE only.
I have also reduced my chemical usage by more than 50 percent with this system. Why is that? A clean pool with polished water reduces the ability of algae and bacteria to grow and fester.
Plus, as mentioned on this site, keeping everything balanced.
Pool supply stores will push you to the cartridge, and especially sand filters. You will use more chemicals with a sand system, and repeat sales of cartridges is the name of the game. A 20lb bag of DE powder lasts me 2 seasons.
As an added bonus, DE powder is used in organic gardening as an insect killer. It wont harm humans, as long as you don't inhale the dust.
Hope this helps a little and good luck.

 

[duraleigh]

ANY type filter will filter dead algae and that is it's SOLE purpose. It will not keep algae out of your pool.

Regardless of filter type, if you have live algae in your pool no filter will ever get it out.

Kill the algae with chlorine and then use whatever type of filter you like to get the dead "carcasses" but do not expect any cartridge to have any affect on live algae in your pool.

 

[Donldson]

You will use more chemicals with a sand system

Not a single bit of truth to this statement. The type of filter used has no effect on water chemistry. There is also far less difference in water clarity between them than many believe, I doubt most could pick out the type of filter used between different TFPC managed pools.