Few service techs look forward to tearing down and cleaning out a D.E. filter, but it's something homeowners absolutely dread, and that spells opportunity. "Most homeowners only have to clean a D.E. filter one time before they decide they don't want to do that anymore," says David Hawes, owner of H & H Pool Service in Dublin, Calif.

Even though cleaning and maintaining D.E., sand or cartridge filters may not be your favorite chore, it must be done in order to deliver what clients want: crystal clear and clean water.

So what's the best way to keep the media in good shape.

The short answer is regular cleaning or backwashing. The long answer, including tips for servicing sand, D.E. and cartridges, follows.

Ancient Media

Sand is the oldest type of filter media - even ancient Greek and Roman baths used water filtered by sand. It's still a solid media today, and perhaps the easiest to maintain, but not so easy to replace.

To keep sand, or any filter media for that matter, performing as well as it should, pool water must be kept balanced. "You want to make sure the water chemistry is kept correct so that we're not building up a calcium cake inside the filter," says Sue Robach, national trainer for Pentair Water Pool & Spa. Water with a pH that's too low can also damage equipment in the filter and elsewhere.

Another good practice is regular backwashing of sand filters when the filter gauge reads 8 to 10 psi more than when the filter is clean (i.e., the starting pressure), although some techs don't even wait that long. "We use 6 pounds as a benchmark," says Hawes. "I leave it up to the technician and I know some go up as much as 8 pounds over, but we've just found 6 to be a good, comfortable number."

In general, pools with sand filters and medium-head pumps should be backwashed before the pressure rises 8 to 10 psi. Says Robach, "A highhead pump can handle when a filter reaches a 10-pound rise. We're adding a lot more friction to the system and a high-head pump can handle that pretty well and still give us the turnover we need, even with a dirty filter. A medium-head pump, however, doesn't perform as well once that pressure gets up to 10 pounds, and what we can do is almost compromise the circulation pattern in the pool. Usually, we recommend backwashing when there's a 7-pound rise on a pool with a medium-head pump."

But be sure not to backwash sand filters before the pressure has adequately increased. "A minor load of dirt in the sand filter actually helps it filter better," says Steve Gutai, product manager for pumps, filters and valves at Waterpik Technologies. "If you backwash too much, you don't allow that top level of dirt to load on the sand bed."

Adds Robach, "This is true with sand, D.E. and cartridges, by the way. What happens is as the dirt coats a sand bed or a D.E. grid or a cartridge, the dirt actually helps hold even more dirt onto that media, and we actually start filtering out finer material. But that doesn't mean you wait until you've got a 50-pound rise in pressure before you clean your filter."

If you're dealing with a problem pool or a pool that has just weathered a big storm or a big party, you may want to use a sand filter aid. "What we do for those pools is use either a cellulose-based product, one of the D.E. alternatives or D.E. I recommend that for clearing up the pool, and when that's all done of course backwashing that material out and then just going back to the normal sand operation."

A poorly sized pump can also negatively affect the sand bed. An oversized pump, for example, may create channeling in the sand. "And of course water is going to take the path of least resistance and it's going to follow those channels and you can actually blow dirt right back into the pool," says Robach.

An undersized pump, on the other hand, may not be able to lift the sand bed enough during backwashing, and as a result, not all of the debris gets washed out.

When sand reaches the end of its life span, which is often three to five years, though it could be longer, it's time for the dreaded chore of changing out the sand. "The sand removal is always the biggest difficulty," says Hawes. "You're trying to work through a hole in the top and many times if we have the ability to, we will remove the filter from the plumbing and tip it over and try to pour the sand out. If that's not possible, we'll use a vacuum to vacuum the sand out, but it's a very tedious job."

Says Robach, "There are some people that just prefer the old-fashioned way and that is a real long arm and a scoop and just scooping the sand out into a bucket and disposing of it. A lot of sand filters also have drain ports on them, so once you get a majority of the sand out, you can hose the rest of it out down through the drain port. Just getting that initial crust off is really the big key because that is what is keeping that sand solid inside the tank."

Then, when adding the new sand, it's a good idea to first pour some water in the bottom of the filter tank. "Once the sand is removed and all the laterals are checked and replaced as needed, we put water in the base of the filter and then pour our sand in carefully to make sure we don't break any of the laterals," says Hawes. "As the sand is poured in, then we add more water, and then more sand and bring that all up. I think that's where a lot of damage happens - if you get in a hurry pouring the sand in."

If both the sand and the filter are nearing the end of their useful life, it may be time for a new filter altogether. Says Hawes, "Sometimes we'll work with the homeowner in terms of the type of filter and the age and say, 'For the cost of the sand replacement, it may be time to look at a new filter or a bigger filter.'"

The Messiest Media

While backwashing is a reliable method of maintaining sand for a number of years, it cannot be relied upon to truly flush all the dirt and debris out of a D.E. filter.

"If we have situations where maybe we've got some oils that are in the pool, the D.E. doesn't have a tendency to want to fall off the grid as well, and especially during that backwashing process," says Robach. "Oftentimes, too, we may find a situation where maybe a pump is sized a little bit too large and we're actually pushing and embedding the D.E. cake somewhat into the fabric of the grid. So because of those two things, we may not get all of the D.E. out of the filter when we backwash. And sometimes people just don't backwash long enough."

To be sure they do get D.E. filters spick-and-span, techs should break down and clean out D.E. filters either twice a year or annually. Backwashing can be used as a stopgap measure in between, and when it is, you probably don't want to re-earth the filter with as much D.E. as you use just after it's torn down and cleaned because too much D.E. can result in bridging or otherwise compromise flow and/or filtration.

"What a lot of guys will do is if, for example, we're talking about a 60square-foot D.E. filter, we know it needs 6 pounds of D.E. That's 1 pound for every 10 square feet," says Robach. "If we backwashed that filter, some guys will say, 'Well, this time, because it's the first backwash I'll only put in 5 - pounds, assuming that about a half a pound is still in that filter.' They just don't put in quite 6 pounds and then after a six-month or year cycle, when it's time to break it down and clean it, we still shouldn't have compromised the water flow going through that filter system."

Before backwashing or tearing down and cleaning out a D.E. filter, be aware and follow local codes and ordinances. In many municipalities, it's not acceptable to hose off grids in driveways, because it can end up in rivers, lakes and other water supplies.

Just as with sand filters, it's critical to have an appropriately sized pump. "If the flow rate is too low for the D.E. filter, the D.E. will not coat on the grids evenly," says Gutai. "And if it's too high, you'll have issues with overly compressing the D.E. grids."

While D.E. does filter down to 3 to 5 microns, which makes it the media that captures the smallest debris, "it's absolutely the messiest to service and clean," says Gutai. (But at least you get paid to do it.)

Hawes describes the steps he takes when cleaning out D.E. filters: "First, we turn the system off, and if it's a computer-controlled system, make sure it's in the service mode so that nobody in the house walks by and sees their filter is off and turns it on while we're in the middle of working on it. Then we open up the drain plug on the filter, and open up the air relief so that the water can drain out and make sure there is no pressure in the filter.

"Once the tank is drained or while it's draining, we remove the clamp that holds the filter together. Then we remove the lid and, depending on the size of the filter and the type of filter, we will either remove as a complete unit the grid assembly or if it's too heavy or too tall, we will remove the manifold and then just remove the grids one at a time. Then we hose out the tank, and before we hose off the grids real well and spray them down with a material that we use to loosen up any mineral or oil deposits, we do try to lift off the main portion of the D.E. and put it in garbage bags.

"Then we hose down the grids again, and clean and lubricate the tank O-ring and make sure the O-ring seat, which is that part of the filter that curves out for the O-ring to sit on, is completely clean. Then we put on the O-ring, put the grid assembly together, install the grid assembly, put the lid on, put the clamp on and tighten it to the manufacturer's specifications. Next, we put the drain plug in, turn the system on, bleed the air out and close the air relief. When we add the new D.E. through the skimmer, we make a slurry mix with D.E. and water and then pour it in."

On The Rise

With various ordinances making it difficult to backwash filters and dispose of D.E. in some cases, it makes sense that cartridge filters, which are not backwashed, are becoming more popular every year. Cartridges are also quite easy to clean and they filter particles as small as 15 microns - a couple more reasons why customers are choosing these filters more often.

In fact, according to annual APSP industry statistics for filters, cartridge filters outsold sand and D.E. filters every year from 2000 to 2004.

Cartridge filter sales continue to grow, in part because of their ease of use.

Although they're not difficult to clean, Hawes stresses that it does take a little while to get all the dirt and debris out of the elements. "My homeowners, I love them to death, but it only takes them 15 minutes to clean the cartridge filter the first time and they put it all back together and then they tell me a week later that their pressure is back up. Well, it's because all they did is just barely spray off the outside. Cleaning four large cartridges takes some time. This is a long process, and by that I mean an hour and a half to two hours, because you need to get in there nice and deep and get the pleats clean. If you just spray the outside off and put them back in, 90 percent of the cartridge hasn't been cleaned. But if you clean it really well with water and a high-pressure nozzle, and you clean it regularly, that will give you probably the maximum life on your cartridges."

It's important to remember that you do not need to do a chemical treatment on cartridges every time you clean them. "You can usually just use a garden hose and water and hose them down," says Robach. "The only time you want to do a chemical treatment on a grid or a cartridge is when you've cleaned the filter system and it's short cycling. In other words, all of a sudden the pressure starts rising quicker than it used to. When people do a chemical treatment every time they pull an element out, what will happen is that acid treatment actually starts breaking down the polymers of the end caps of the elements, or sometimes can break down the internal structure of the cartridge and it makes them brittle and so they'll have a tendency to collapse sooner. So we never want to acid wash unless we absolutely need to.

"When it does come time to do some type of chemical treatment, keep in mind there are two different things that'll build up on that element: oils and/or calcium, and they're treated differently. If there are oils in the pool, we want to degrease it first, and then we want to remove the dirt and calcium with some type of acid product. The reason for that is if we don't remove the oils first and we do an acid treatment on the cartridge, we set the oil into the fabric and that shortens the life of the filter cycle."

Hawes says it's critical to stress to clients that elements don't last forever. "We always try to let people know cartridges are great, they do a good job, but you need to understand that after so many years, you're going to have to replace them."

On a pool with well designed hydraulic system, Robach says elements can last anywhere from two to 10 years, depending on the element and the filter and how they are treated. "It's hard to say exactly how long a cartridge will last," she says. "It depends on how well you take care of it, and that's true with everything. How long does an engine in a car last. It depends on how you take care of it."

So just like car engines, all types of filter media will perform better and last longer when they're maintained in a timely and appropriate manner.