| When should a cartridge filter be acid washed? |
 Acid
washing is perhaps the biggest single factor leading to premature filter
cartridge failure!
For years, service technicians and homeowners have acid washed D.E. grids.
However, cartridge elements do not have the protective D.E. powder coating
that grids have and can be permanently damaged by the acid. As a rule of
thumb, acid wash only when required, if at all, and never without
thoroughly cleaning the element with a cartridge degreaser first.
Here's a simple test to determine if acid washing is required;
After thoroughly cleaning the cartridge with a degreasing agent, flush the
cartridge with a garden hose to remove all traces of soap, etc. Now apply
several drops of acid directly to a small area of the filter media. If
bubbling occurs, this indicates a build-up of calcium or minerals, and you
should proceed with a mild acid soak (see Unicel Cleaning Instructions for
more details). If no bubbling is observed, your cartridge most likely does
not require acid washing. |
| Is there an easy
way to know when to clean a cartridge filter? |
 Cartridge
filters work on the clarification process.
They utilize the debris they collect as an aid to improve filtration. As a
result, cleaning too often does not allow the filter to work at optimum
filtration efficiency, while not cleaning often enough will shorten the
life of a cartridge element.
So here's a tip.
When you replace the element with a new one, note the start-up pressure on
the tank gauge. This reading is the system's total pressure in
"pounds per square inch" or psig (gauge). Mark this point with a
drop of fingernail polish or a grease pen. Then add 8 pounds to the
reading and place another dot. You now have the normal operating pressure
for your cartridge in psid (differential). Allow the filter to operate
between these two points and clean whenever the gauge reaches the higher
pressure mark. |
| End Caps - Some cartridge end caps are hard and
others are soft. Some cartridges have one hard end cap and one soft end
cap. Why is this? |
When cartridge manufacturers design a new
filter element, several factors must be considered. One of the most
critical is the end cap hardness.
To determine the exact degree of shore hardness required, we first must
look at the element sealing points. Sealing points both position the
element and prevent water by-pass.
Historically, single cartridge systems all used cartridges with inside
i.d. friction seals with hard end caps. This design provided both strength
and pleat support. However, as filters became more sophisticated, so did
end cap design.
Sta-Rite's Posi-Flow element, for example, uses a soft vinyl bottom to
both seal the inside and outside edges and lock the cartridge into the
filter base, while the top end cap is a hard compound for cartridge
strength and integrity. Hayward's Star Clear filter uses hard end caps for
integrity with a soft gasket to allow a knife edge top seal. Both the new
American Predator and Jacuzzi CFR designs rely on a soft top and bottom to
achieve an o-ring seal. These end cap configurations are excellent
designs. Only the compounds change to meet the manufacturers'
specifications.
This is another reason why Unicel builds its replacement cartridges to
OEM design specifications, and why Unicel is number one in quality and
reliability. |
| What does the term
"plumbed backwards" mean and how can you tell if your system is
plumbed backwards? |
 Simply
put, waterlines that attach to the "inlet" and
"outlet" on the filter canister were reversed during
installation. In this case, the water flow through the filter element will
be from the "inside-out" rather than the "outside-in"
(as the filter was intended). Debris rapidly accumulates on the inside of
the pleats, water flow is restricted, and the cartridge begins to expand.
Eventually, the cartridge's end cap will split, releasing the internal
pressure. The filter element is now being by-passed in the filtration.
- Is the nature of the split in the end cap similar to this?
- Peel back the broken top and examine the pleats. Is there dirt
accumulation on the inside of the pleat pack?
- Does the support band on the outside of the cartridge, if present,
appear stretched and wrinkled?
- Do the outside of the pleats appear rounded and puffy?
If you are still not sure if your filter is plumbed backwards, shut
down the entire system and completely bleed the canister pressure. Remove
the cartridge and with the lid off quickly turn the pump on and off.
Observe which port is delivering the feed water and assure that it is the
"inlet." (Always consult the manufacturer's instructions before
removing the canister lid or working on any pressurized system.) |
| I saw a new filter cartridge made with yellowish
material. What is this and why are Unicel cartridges white? |
| Unicel and virtually every brand name company
in the filter business uses a spunbonded, 100% polyester material called
Reemay® as their filter medium. Reemay®, which has FDA compliance, is
approved for milk filtration and is white to indicate purity. The
yellowish material (technically also a spunbonded polyester nonwoven) is
less expensive.
Some low-end manufacturers are utilizing this material to reduce costs;
however, there is a significant difference in performance. |
| How can I tell when a cartridge filter element
needs to be replaced? |
 With
no moving parts or electrical switches to fail, cartridge elements do not
have a defined termination point. Instead the fine interstices of the
media matrix gradually plug up over time. In a typical spa, the culprit
that plugs the media is perspiration and body oils combined with soaps,
chemicals and very fine particulate. In a swimming pool, the loading is
primarily debris along with sun tan lotions and organic matter such as
algae.
Assuming the filter is properly maintained and correctly sized to the
pump, determining when the cartridge is exhausted depends primarily on
three factors:
- Shorter cycle time between cleanings
- Low water flow rate and high differential pressure
- Catastrophic failure such as a tear in the media or center core
collapse
All three are dependent upon proper pool or spa water chemistry and
following a routine maintenance schedule. Homeowners should be reminded
that filter elements are plastic and should be handled and maintained
accordingly.
To maximize the life of a cartridge I suggest:
- Clean the elements per cleaning instructions.
- Never use a stiff brush to scrub the media.
- Maintain pool or spa water chemistry in proper balance.
- Do not allow the differential pressure to go over 8 psi between
cleanings.
- Alternate two sets of cartridges when cleaning.
|
| Sharp pleat folds vs. rounded pleats — is
there a difference? |
| Absolutely! One of the first things a
filter expert will look for when examining a pool or spa element is the
pleat fold or "knuckle radius" of the pleat. Why is this
important? If you look carefully, you will notice that some manufacturers'
pleats are very sharp while others are rounded and even appear puffy. With
Reemay or other spunbonded polyester medias it is much easier to make a
rounded fold than a sharp pleat. Moreover, a rounded fold can mask the
filter manufacturer's inability to make straight pleats or maintain proper
pleat spacing.
Unicel takes great care to make sharp pleat folds for the following
reasons;
- Cleanability:
sharp folds increase the spacing between pleats making it easier to
flush out loose debris.
- Eliminates bridging:
allows particles to get down into the pleat instead of laying across
the top of two or more pleats. This assures maximum dirt holding.
- Full utilization of the pleat surface:
allows debris to build up from the inside out, critical to obtaining
the maximum cycle life between cleanings.
Maximizes flow, minimizes pressure loss - by decreasing the surface
contact between the inner pleat knuckle and center tube.
* This information pertains to elements
made of spunbonded polyester. Paper type media is not considered in this
presentation. |
| Support bands — why are they put on some
cartridges and not others? / What if the band breaks or comes off? |
 The
bands you see on swimming pool cartridges are added to prevent pleat
flutter caused by turbulence inside the canister during the filtration
cycle. In addition, bands maintain pleat spacing and make cartridge
cleaning and maintenance easier.
Skim filters used in spas rarely require bands. This is because the
water flow through the element is under less pressure and is more laminar.
Furthermore, the generally smaller size of cartridge used in skim filters
can actually make separating the pleats for cleaning more difficult if
held firmly in place by a band.
On a well-made cartridge, the bands are carefully adhered to the outer
edge of the pleat knuckle and rarely come loose or break in normal use.
However, acid soaking or rough handling can cause the bands to break and,
in some instances, even separate from the element.
A split band - even if broken in several places - will not affect the
filtration performance of the element and is not considered a cause to
warranty the cartridge. Loose or missing bands is often a sign that the
cartridge is worn out and can be a good indication that it's time to
replace the element.
Here's a quick tip. When buying a new filter, place your thumb
between the pleats and under the band to check for adhesion. The band
should be firmly attached and not separate easily. |
| What is the procedure to clean my cartridge (chlorine
and bromine spas)? |
|
- Remove the cartridge from the filter housing following the
manufacture’s instructions.
- Use a garden hose with a straight flow nozzle to wash down the
filter element. Work from the top down, holding the nozzle at a 45
degree angle, and wash all the pleats with emphasis between pleats.
- Rinse until all dirt and debris is gone.
- For all spa cartridges and elements used in swimming pools where
perspiration, suntan lotions, and other oils are present, soak the
element for at least one hour (over night is more effective) in (1) a
commercial filter cleaner; or (2) one cup trisodium phosphate (TSP) to
five gallons water; or (3) once cup dishwasher detergent to five
gallons of water.
- Rinse the cartridge again to remove oils and cleaning solution.
- If the filter has a coating of algae, calcium carbonate (residue
from calcium hypochlorite), iron, or other minerals, soak the
cartridge in a solution of one part muriatic acid to twenty parts
water until all bubbling stops. WARNING: Failure to remove all oils
and cleaning solution before acid soaking will result in a permanent
restriction of water flow and cause premature cartridge failure.
- Rinse the cartridge clean an reassemble housing.
WARNING: Wear rubber gloves and safety glasses when using
acid and chorine. Do not add water to acid. Do not mix chlorine and acid.
NOTE: Unicel does not recommend the use of diatomaceous earth (DE) with
cartridge filter. DE particles will become trapped in the body of the
media and shorten cartridge life. If desired, a cellulose fiber (synthetic
DE) can be used in moderation.
|
| Is there a glossary of filter terms? |
BACKWASH
The process of cleaning the filter medium or septum by reversing the flow
of water through the filter.
BASECOAT
A layer of filter aid between the precoat and septum.
BLINDING
Filling in and clogging of a filter medium caused by entrapment of
particles from a filtered liquid. When the medium becomes
"blind," an increase in differential pressure and reduction in
flow results.
BRIDGING
Debris which arches, or bridges, the individual pleats in the filter
cartridge or between two filter elements.
Cartridge Filter
A filter that utilizes a pleated, porous medium as a filtering material.
Clarification
The process by which the filter removes progressively smaller particles on
each successive turn over, thus improving efficiency and extending the
cycle life. Cartridge filters use the clarification process.
Clarifier (also called coagulant or
flocculent)
A chemical that coagulates and neutralizes suspended particles in water.
There are two types of clarifiers: inorganic salts of aluminum or iron and
water-soluble organic polyelectrolyte polymers.
Coagulation
The process by which very small, finely divided solid particles -- often
colloidal in nature -- are agglomerated into larger particles.
Compressibility
Degree of physical change in a filter cake when it is subject to pressure,
resulting in increased differential pressure and reduced flow.
D.E.
Abbreviation for diatomaceous earth. Fossil-like skeletons of microscopic
water plants called diatoms.
Denier
The relationship between cross sectional area and weight. Denier is
numerically equal to the weight in grams of 9000 meters of individual
fiber (i.e. 1 gram equals 1 denier). Most filtration grade Reemay use 4
denier fibers. These fibers are approximately 28 microns in diameter.
Differential Pressure
(1) The difference in pressure between two given points. (2) The combined
pressure caused by the debris, filter cake, precoat and septum, expressed
as ("delta P"). (3) The effluent pressure minus the influent
pressure.
Effluent
Fluid which has passed through a filter. Also called the filtrate.
Enzymes
An organic protein, also known as amino acids. Enzymes are non-toxic and
biodegradable. Although they are not an oxidizer or clarifier, enzymes
significantly reduce cartridge maintenance by breaking down oils into
carbon dioxide and water.
Feed
The mixture of particles and fluid that is introduced into the filter.
Terms used synonymously include "influent" and "incoming
slurry."
Filter
Verb: To pass fluid containing suspended particles through a filter medium
whereby the particles are separated from the fluid. Noun: A
"device" for carrying out the filtration process, consisting of
the filter medium and suitable hardware for constraining and supporting it
in the path of the fluid.
Filter Aid
Any material (usually diatomaceous earth) that enhances the separation of
solids from liquids in the filtration process.
Filter Cake
The combined layers of solids, precoat, and debris removed in the
filtration process and accumulated on the surface of the filter medium.
Filter Cycle
The operating time between cleaning or backwash cycles.
Filter Medium
The permeable material such as diatomaceous earth, sand, or polyester
nonwoven material used to separate suspended particles from liquid.
Filtrate
Fluid that has passed through a filter. Also called the effluent.
Filtration
The process by which particles are separated from a liquid by passing
through a permeable material.
Filtration Rate
Flow in gallons per minute (GPM) through one square foot of filter medium.
For residential pools, the filtration rate should be 2 GPM per square foot
of D.E. filter surface area and 1 GPM per square foot of cartridge filter
surface area. For most commercial pools, the filtration rate should be 1
GPM per square foot of D.E. filter surface area and .375 GPM per square
foot of cartridge filter surface area.
Flocculation
The process by which small dispersed particles combine together to form
larger size particles which can be removed by the filter. The result of
adding an electrolyte to the water.
Hydrophilic
Water accepting. The ability to absorb water.
Hydrophobic
Water rejecting. Lacking affinity for or ability to absorb water.
Influent
Dirty or unfiltered water introduced to the filter. Also referred to as
"feed" or "incoming slurry."
OEM
Original Equipment Manufacturer or brand name.
Micron Size
Expressed as micrometer (µm), a unit of measurement equal to 1/1,000,000
of a meter (.0000394"). 40 micron is considered the smallest size
particle visible to the human eye. A red blood cell is 6-8 micrometers
large; one grain of table salt is roughly 100 micrometers in size.
Permeability
Expressed in cubic feet per minute (CFM), the resistance to flow through a
media. The lower the perm number, the greater the resistance. The
permeability of a filter media is a quality control measure for cartridge
and D.E. filter materials.
Polyester
Long chain synthetic polymer composed of at least 85% by weight of ester
of dihydric alcohol and terephthalic acid.
Polymer
High molecular weight organic compound whose structure can be represented
by repeated small units. Synthetic polymers are formed by condensation
polymerization of monomers. If two or more monomers are involved, a
copolymer is formed.
Porosity
(1) The degree of open area between the fibers. (2) The void area which
exists in the structure.
Precoat
The layer of filter aid (usually D.E.) formed on the media surface by
introducing a slurry (generally between .1 and .2 lbs. per square foot of
surface area) to the medium at the beginning of the filter cycle.
Reemay
A registered trademark of Reemay, Inc. Originally developed by DuPont,
Reemay is made of continuous filament, 100% polyester fibers. The process
by which these fibers are drawn, randomly laid and thermally bonded is
known as "spunbonding."
Septum
A permeable material used to support the filter medium or precoat on D.E.
filters.
Trilobal
The three sided fiber formed by drawing polyester resin through a die or
spinneret. The basic shape of Reemay fibers.
Turbidity
(1) The characteristic or property of a liquid that causes it to absorb or
scatter light. (2) A measurement of water cloudiness or haziness caused by
micro-organisms, algae, or suspended fine particles.
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