Filtration, Sanitation & Circulation

Adult Swim: Learn to Swim America!
by Rob Cox, July 18, 2012

Filtration, Sanitation & Circulation


For clean, clear pool water, one needs a balance of Filtration, Sanitation & Circulation. These three work together to keep pool water fresh and inviting.

It's true that if you have a large DE filter, you can get by with less sanitation and less circulation. Or, if you shock the pool with chlorine daily, the water will be quite sanitary and you'll need less of the other two.

And if you have the circulation of a rushing river, hundreds of gallons per minute in a small pool, the amount of filtration and sanitation needed, diminishes.

Balance is what's important, an equal and fair amount of work is expected from our pump, filter and sanitizers. Here's some ways that you can improve each of these, should they be lacking in any way.


Your pool filter is designed to trap particulate matter and small contaminants. In terms of particle size, DE filters offer the best filtration ability, followed by Cartridge filters, and then Sand filters. No matter which pool filter type you use, having a larger filter than you need will serve you well. If you oversize your pool filter, you get more filter surface area, lower operating pressure and longer time periods between cleanings.

If you wanted to maximize your pool filtration, you would install the largest D.E. filter, either a 60 or 72 sq ft. DE filter. Not planning on buying a large D.E. filter? Here's some tips to improve filtration on your existing pool filter.

  1. Use Clarifier to coagulate small particles into larger, more easily filterable clumps.
  2. Use Filter Cleaner annually to remove oils and minerals from your filter media.
  3. Replace your filter media (Sand, Grids, Carts) when it no longer does the job or time between cleanings increases to an inconvenient level.
  4. Robotic pool cleaners filter as they clean. Many models will filter the water that passes through them, down a very small 2 microns, equivelent to a DE pool filter.


Purifying the water is important because filters cannot trap all pathogens and bacteria that can be present in your pool water, and because many forms of algae and bacteria are not free-floating, but attach themselves to your pool walls and like to hide under ladder treads and behind pool lights.

Proper water balance it also part of the equation. Not only do we need to introduce chemicals that will attack these contaminants, but we also need to create the best aquatic environment through balancing pH, alkalinity and calcium hardness levels. When your water balance is out of whack, chlorine and other sanitizers don't work as effectively, and it creates an environment that is suitable for algae and bacteria growth.

Some pools operate very well with nothing more than balanced water and a 1.0-2.0 ppm chlorine reading. These pools usually have great circulation and filtration helping out. If your pool needs help in the sanitation department, here's some ways to improve purification of your pool water.

  1. Install a Mineral Purifer like Nature2 or the Frog. Silver & Copper ions act as a bacteristat and algaestate, respectively, reducing your chlorine demand, and raising your overall pool sanitation. 
  2. Shock your pool when levels of combined chlorine are greater than 0.3 pm, or if the water smells strongly of chloramines and your swimmers eyes are burning.
  3. Keep a level of chlorine Stabilizer in the water, in the range of 40-80 ppm. Especially important during the hottest months, to shield your chlorine from the sun.
  4. Use an Enzyme, like products from Orb-3 or Natural Chemistry. Just like the enzymes used to clean up ocean oil spills, pool enzymes digest organic matter, oils and invisible contaminants, which reduces the workload for your primary sanitizer and your pool filter.


High flow with no dead spots. Churning and moving water - never stagnant. If you shut off your filter pump for 12 hours per day, as most people do, circulation and filtration stops, and sanitation has to take up the slack. Good pool circulation moves unfiltered water into the suction ports, and distributes filtered and treated water to all areas of the pool.

Older pools can have poor cirulation in some cases. Most newer pools were designed with a few calculations on the pump size and number of suction and return outlets. It's common that old main drain lines can collapse or be sealed up to prevent leaking. Dirty filters or pump baskets reduce flow rates. Connecting pool cleaners that raise the filter pressure slows the flow and inhibits designed circulation patterns and flow rates.

Here's some things you can do to improve circulation in your pool, should it be lacking.

  1. Point eyeball return fittings in the same direction, to create a circular flow pattern around the pool.
  2. Robotic pool cleaners can be a big help, especially in pools with abandoned main drains.
  3. Brush your pool! It not only improves circulation, but de-dusts the surfaces, so it can be filtered. 
  4. Go swimming! Nothing helps circulation quite so much as some active swimmers in the pool.