Its that time of year again, getting your pool ready for the summer, maybe even replacing your original filter and buying a new one this year. If you have been running a sand filter but have been thinking about changing over to the D.E. filtering system and are not sure, this article will explain the differences. What are the Differences Between Sand and Diatomaceous Earth (DE) Pool Filters?
Sand will filter to 30 microns
D.E. filters down to 3 microns
Sand is back washed without losing media
D.E. needs to be recharged when you backwash & loss DE needs to be captured.
Sand is replaced 3-5 years.
D.E. has to be completely torn down once a year
Sand is more economical & practical
D.E. is costly
DE Filters use a combination of DE powder, also known as Diatomaceous Earth, and sometimes referred to as “dirt” Water is filtered through the media, DE, which is a sedimentary rock composed of chemically inert fossilized, skeletal remains of billions of microscopic organisms called diatoms.
What is Diatomaceous Earth Used For
Diatomaceous Earth (DE) is a white clay-like powder found in various areas around the world. Diatomaceous Earth is composed of diatoms, a specific type of hard-shelled fossilized algae. Diatoms, at one time, served as a primary aquatic food source for marine life. There are many uses for D.E.
As these diatoms died, their exoskeletons fell to the bottom of the seas and became fossilized. Eventually, after millions of years, large deposits of the fossilized rock formed into what we now know as diatomaceous earth or D.E
Diatomaceous is a very fine powder and is very light due to its’ high porosity. DE contains between 80-90% silica, 2-4% alumina, and 0.5-2% iron oxide. The remaining percentage is mostly traced minerals like calcium, zinc, copper, and magnesium.
Food grade diatomaceous earth, the only form safe for human use is a white powder, while other forms of diatomaceous earth may have a brown/reddish tint. The Food Grade form of DE is the highest grade of it.
Besides pool filter Media, Diatomaceous Earth has many uses. In food processing and its used as a filtering agent to remove impurities from a variety of foods and drinks such as beer and soda. They are used in toothpaste and polish agents along with cosmetics. They have the ability to absorb water and the Food and Drug Administration endorses it as a safe way of dealing bugs instead of insecticides.
Diatomaceous earth is also quite frequently used as an insecticide and pest repellant in home gardens and on large-scale farms. Diatomaceous earth actually has sharp edges, which look like shards of glass under a microscope. There are forms of DE that are used in powders and in medicines that are used on pets that will keep pest off of them.
The sharp edges of the D.E. scratch the exoskeletons of insects, which cause insects to lose fluids and die. Diatomaceous earth also has the ability to absorb fluids rapidly, which means insects either have to flee the area or they die very quickly.
Diatomaceous earth can also be used in the same manner naturally as a pest repellant on animals. A simple coating applied to an animal’s fur is more than enough to kill any existing pests and prevent future pests from affecting dogs and cats.
Diatomaceous Earth can also be used to flush the human body of impurities, detoxing or cleansing. It has the ability to purge the human body of toxins and heavy metals. This allows the human body to operate efficiently and to improve overall health.
Backwashing DE Filters
Most sand filters require from 50lbs up to 300lbs of sand, depending on the filter size. Once filled, the sand can last 3-7 years according to use.
One big difference between Sand and D.E. is that Sand is reusable and can be backwash and cleaned. In a D.E. system, it can’t.
Once the filter dirties up, it is lost and needs to be replaced by the pool operator with new Diatomaceous Earth.
There are 2 basic kinds of DE filters the Bump and the Backwash. The theory behind the bump type is that when the filter gets dirty, 25% above the clean pressure, you ‘bump’ the dirty DE off the grids so it can mix with the dirt and then re-coat the grids with dirty DE. Its a way to try and get around the job of tearing it down. But…….
If the pressure does not reduce, then the filter should be torn down and cleaned anyways. The other type is the Backwash type and when the filter pressure rises 25% above the clean pressure you need to flush the DE and dirt out of the filter by backwashing.
After each backwashing, you will need to replace about 50% of the total DE. Be aware that some townships require a DE separation tank for back-washing DE filters. This can add to both the expense and the space they take up on your equipment pad.
Backwashing Sand Filters
With a Sand Filter, as the Sand gets dirtier the flow will decrease and the pressure will start to rise. This is an indication that it’s time to backwash. The pressure rate will increase to about 7-8 lbs. over the normal operating pressure. D.E. Filters also work off the pressure gauge.
After backwashing a D.E. filter, the dirty filter powder is discharged, and a new D.E. filter powder is added to the filter, by pouring it into the skimmer directly or you can mix it in a bucket with pool water.
The gauge will indicate the need to backwash just a Sand Filter gauge would. With DE Filters once the pressure gauge reads 8-10 pounds over the start-up and normal operating pressure then its time to backwash the D.E. Filter.
Sand can filter down to around 30 microns in size. so D.E. filters have that advantage of filtering the pool water to the smallest microns and will keep the water cleaner and clearer than any sand media could but additives can be used to lower the microns and raise the efficiency of Sand.
Diatomaceous Earth Pool Filter Problems
A disadvantage of the D.E. filter is that it requires the most amount of maintenance. DE powder is always needed after backwashing.
Some states require a Separation Tank when using a DE filter to keep DE powder from streams or sewers. Your D.E. System may need a Separation tank like this one from MyWaterEarth& Sky and Amazon. Hayward D.E. Separation Tanks are ideal for water conservation and savings during backwashing by returning chemically treated backwash water to the pool.
Hayward D.E. separation tanks hold up to 10 lbs. of used D.E. filter powder and compliment both New and existing vertical grid D.E. filter installations.
Also with a DE Filter, you typically have to take apart the filter once or twice per year, to clean the filter grids or tubes with water. Typically a good wash with the garden hose is all that’s needed.
This filter definitely requires the most of maintenance but it will filter the water to the smallest micron size, around 2-3 microns. Although DE filters are the most expensive to purchase, and they require more maintenance than other types, they are the best form of filtration available.
The D.E. powder is poured into the skimmers and will soak inside the filter applying a coating to the panels on the grid inside that will filter the pool water. The normal amount after backwashing for a medium to the large pool is around 8 lbs.
DE Powder in Sand Filter
Diatomaceous Earth, used in D.E. pool filters, can also be used in Sand filters to trap particles down to 3 microns in size. Use 1-3 cups depending on your filter size, by pouring it into the skimmer after backwashing, and it forms a layer on top of and down into your sand bed. Also useful, and some say better to use is Aqua-Perl, a volcanic mineral filter aid used as a substitute for DE powder.
There are plenty of aids that can be used with the Sand media in your filter. Clarifiers with polymer added can with just a couple ounces a week to improve your Sand media or D.E. to add more efficiency and a noticeable difference. The polymer will attract particles so they stick together. Once together they are easier to remove from the pool system. The DE will help the Sand polish the pool just like the Clarifier or Gel Bag which take filtering down further to about 1 micron.
The Slime Bag™ is another filtering product like D.E. that features a unique combination of material that allows it to filter particles as small as 1 micron, while returning the clean water to your pool, allowing you to completely clean your pool without dumping water and money down the drain. Once you get the Diatomaceous Earth in the Sand Filter you can use this instead of buying other products that will only do the same thing.
Small amounts of DE can be added to a High-Rate Sand Filter after each backwash to add efficiency to you filtering normally lost with sand. Figuring out how much DE to use:
- Start by noting the PSI reading on the filter with the pump running.
- Mix 1/4 cup of DE with water in a bucket and pour that slowly into the skimmer. Remove the skimmer sock, if any, before adding DE.
- Give the system about two minutes to stabilize.
- Note the pressure on the filter and repeat the second and third steps until the pressure has gone up by one PSI. This will typically take around 1-2 cups of DE.
The first time you try this keep a keen eye on the pressure gauge for the next 24 hours so that it doesn’t shoot up too fast. Make sure that DE that you use id the kind for swimming pool use.
Diatomaceous Earth is an option that is often used when the size of the swimming pool is a little smaller and the usage is a little less than normal than a larger size swimming pool.
Bigger type public pools are normally High-Rate Sand Filter systems and for good reason. Even though the results of D.E. systems are very good the maintenance time and cost are somewhat too much. There are many products like the Slime Bag, Clarifiers and Diatomaceous Earth Powder that when added to Sand can bring it up to the filtering efficiency of a whole D.E. Filter System.
Sand is a standard for bigger type pool filters and is practical, economical and for me the best and easiest way to keep my inground pool looking great every year.
How long do pool filters last?
With basic maintenance, a High-Rate Sand Filter can last 10 or 12 years if you change Sand ever 5 years or so and break it down every winter properly.
How often do you clean a pool filter?
DE filters should back-washed after one to three months of use, or after the filter has built up 8–10 PSI of pressure over start-up pressure. You should also dismantle and clean the D.E. filter at least once a year. Depending on usage
How often should you backflush a pool?
As a rule of thumb, you should backwash and rinse your filter about once a week. The optimal time is right after you vacuum the pool. A rise in pressure and high usage.
Jim has over 30 years in Water/Wastewater & Water Filtration Business and has written over 250 articles on the World Wide Water Situation and has owned a 45,000 gal Inground Concrete Swimming Pool for 30 years.