Filters aren’t particularly glamorous, but they are necessary to keep the showier equipment from becoming clogged, the system from accumulating too much head pressure or beautiful fountains from becoming bespeckled.

To help this steadfast category along, pool and spa professionals need to be well-versed in everything from installation to cleaning. These guidelines cover such basics for filters in all types of projects, including high-end aquascapes and their special needs.

All types of installations

Here are some general pointers for sizing and service of the typical filter you would encounter out in the field.

  • Follow basic hydraulic principles.

When basic hydraulic principles are observed, every piece of equipment benefits, including filters. However, too much water flowing too quickly through the unit will cause premature damage. “It hammers it too hard,” says Paul Palubicki, owner of Paul’s Pool Service in Orinda, Calif.
Reduce the chance of this happening by using large filters and plumbing, and smaller pumps. This slows down the flow, decreases head pressure and helps the filter trap more material.

Too much flow also keeps the filter from working at its best. “If you have [too large a pump] pushing water through there, it’s going to force the dirt back into a cartridge filter, and that’s not what you want,” says Ken Whitlow, owner of Watercolors, LLC, in Atlanta. “You want it moving slowly, so it’s caught on the outside of the cartridge, but not pushed inside.

“Then, when you turn the filter off, a lot of dirt will drop down to the bottom,” he adds.

If one unit won’t suffice, use two. Run them sitting next to each other — and divert half the water to each one.

When sizing a sand or diatomaceous-earth filter, be sure to consider the backwash rate. It’s generally less forgiving than the posted flow rate. “For filtering, as long as you’re not going over the maximum, the minimum is almost immaterial,” Palubicki says. “You can take a 6-square-foot sand filter, which is huge, and put 10 gallons per minute through it, or probably 200 with no trouble. But there’s less of an acceptable range for backwashing.”

Plumbing that leads to the filter should contain as few 90-degree fittings as possible. This reduces turbulence. If you must use an elbow, don’t place it right next to the filter’s union. After leaving the bend, the water needs a little time to smooth out.

  • Clean the filter thoroughly.

Clean the filter during or immediately after pool start-up to get it off on a solid footing. “That’s a good time to clean it because you’re loading the filter up with silt and soot,” says Blake French, who owns Millennium Pools of Austin in Texas. “With pebble [finishes], we get a lot of little pebbles that we suck into the tank.”
Afterward, there’s no prescription for how often to clean a filter. It depends on the manner and frequency in which the vessel is used. Just make sure that when the time comes, you do it right. Avoid the temptation to simply backwash or clean the cartridge.

“I’m always cleaning up inside the actual filter canister itself,” says Ed Penfield, president of Aqua Island Technologies, a service firm in Bellingham, Wash. “It has film, crud and hair, and all these things that can harbor and colonize bacteria.”

Penfield hoses out the container first. A brush may not reach into every nook and cranny, so he uses a more flexible scrub pad to slough off any unwanted matter. “If it’s been neglected, I might have to do a wash-down with a dilution of sodium hypochloride,” he says. Then he performs a final rinse and reinstall.

  • Don’t oversize spa filters.

If you oversize a filter, it helps reduce unwanted pressure while lengthening the span of time between cleanings or backwashings. Don’t get carried away, though. Penfield has noticed that many builders use the same size unit for the pool and spa.
In the case of sand or DE filters, they may be so big that it takes the entire spa’s water to backwash. “To try to get a big sand filter like that backwashed, you’d probably dump the whole spa,” Penfield says. This causes a hassle for homeowners and service technicians, who may backwash the filter less often than needed.

Result: Too much gunk builds up. A biofilm, which is a slimy protective shield that bacteria put around themselves to help them colonize more easily, can form. In addition, it can cost more, take up unnecessary space and waste water, Penfield adds.

When designing a system, take the extra time to size the filter to the spa. Don’t simply duplicate what the pool needs.

  • Minimize maintenance.

Consider future maintenance issues when installing a filter.
“With DE and cartridge filters, you’ve got to get half the shell off the top to be able to service them, so you need to watch out for head space,” says Steve Oliver, president of Creative Water Concepts in Scottsdale, Ariz. “The filters themselves should be 6 inches away from a wall, and you need the ability to remove a band clamp if necessary.” If possible, leave closer to a foot of clearance around the filter.

It’s also important to identify a place where sand and DE filters can be backwashed. Don’t simply assume the homeowner or tech will figure it out. “It doesn’t do much good to put that kind of filter on a pool that has no place to backwash it, such as next to a creek, a street or in million-dollar landscaping, where the customer will not allow you to backwash,” Palubicki says.

If there’s no acceptable spot to backwash, use a cartridge filter — or create an area to perform the task. A hidden pit will do the trick. “[Line it with] a geogrid material that will keep the roots from trees and bushes from getting inside, then just fill it with rock,” Palubicki says. “Place geogrid on top and 6 inches of dirt, and you can put lawn on top of it.

“Plumb the sand filter, so [the backwash] goes right inside the pit underground,” he adds. “If you have to dig it up, you dig up lawn. No big deal.”

High-end installations

Vanishing edges, waterfeatures and other more complex aquascapes often require extra filtration. Use these helpful tips:

  • Install a separate filter for a vanishing edge.

If you think it’s OK to just install a filter with your circulation pump on a vanishing-edge pool, think again. A vanishing edge performs like a large skimmer and attracts all the dirt and debris that congregates in the pool. The last thing you want is for debris to enter the vanishing-edge pump.
With a separate system, water moves from the catch basin and then the filter before going back to the main pool. “It’s just as important for the negative edge to have a filter on it as any other pump,” Millennium Pools’ French says.

“A lot of soot, leaves and biodegradable products that get in your pool would normally end up over the edge,” he adds.

  • Equip waterfeatures adequately.

Your filter choice depends on the project. If water shoots out of a smaller, narrower orifice, such as deck jets, bubblers and some sheet falls, you’ll need to filter out even the finest particles. Otherwise, the hardware will clog, preventing proper flow.
Some waterfeatures need more help sifting out larger debris. “A lot of fountains or waterfalls are not connected to a chlorinated system,” Palubicki of Paul’s Pool Service notes. “You could have less of a filtration system, but one that’s going to work with something that will get heavily loaded.”

If that’s the case, Palubicki might take a sand-filter shell and fill it with a coarser than normal grade of sand, or even gravel. He’ll sometimes use the bio-balls that can be found in ponds. “Even a large sand filter would tend to clog in just a couple of days,” he says. “If you have a fountain that has 300 gallons, and it takes 200 to backwash, it doesn’t quite make sense.”

Stream beds collect a lot of debris, too. To keep it from entering the filter, Watercolors’ Whitlow likes to pre-filter the water as it runs through the rocks. He’ll make the last pond deeper than the others so the sediment can settle there. A service tech or the customer can vacuum it out later.

“Before it drops over a ledge into the pool, it’s almost like a collection plate,” Whitlow says.

  • Upsize the filters on complicated waterscapes.

Intricate networks of water tend to attract large amounts of matter. This occurs more often if they fall over a lot of rocks, are surrounded by plentiful plantings or situated in high winds.
That’s why Oliver of Creative Water Concepts generally oversizes filters on pricey projects. “I inevitably upsize systems,” he says. When using sand or DE, be careful not to oversize the unit so much that it requires the whole body of water to backwash.

  • Factor lighting into the filter equation.

Designers put a lot of time and equipment into their lighting. Thus, they don’t want their well-thought-out nightscape thwarted by the sight of tiny particles floating around in the water.
“Light illuminates and has a tendency to draw dust toward it for those that are of a high-heat wattage,” Penfield of Aqua Island Technologies says.

For pools or waterfeatures that put a premium on lighting, Penfield recommends DE or cellulose fiber. This type of media sifts out the smallest particles possible.