This document provides information about sand filters for pools: - Sand filters are the second most common type of pool filter and can filter particles down to 30-40 microns. They require cleaning every 3-5 years on average. - Sand filters have a filter tank and multiport valve that controls water flow. The valve can be mounted on top or the side of the tank. - The multiport valve has settings for filter, backwash, rinse, waste, recirculate, and closed that determine how water flows through the system. - Proper maintenance includes backwashing when pressure increases and chemically cleaning the sand twice a season. The valve seat gasket is the most common part to fail

1. PEN202: SAND FILTERS
Pool & Spa University

2. QUICK REVIEW
➤ The pool filter is the largest
medium in the pool for catching
small debris. Filtration is one of
the primary keys to proper pool
care, making the filter second
only to the pump in terms of
equipment importance.
➤ Three types of filters exist:
➤ Sand filters
➤ Cartridge filters
➤ Diatomaceous earth (DE)
filters
➤ This course will cover sand filters
in particular.

3. SAND FILTER OPERATIONS
➤ Sand filters comprise approximately 29% of the total installed
filter types in the US, coming in second only to cartridge
filters.
➤ Of all filter types, sand filters work to the largest filtering
capacity, approximately 30-40 microns.
➤ Alternate replacement media types like VitroClean crushed
glass can provide even better filtering results without any
equipment replacement.
➤ Media lifespan for sand filters is roughly 3-5 years, depending
on usage and care. Heavy-use pools may need to replace
media more often.

4. HOW SAND FILTERS WORK
➤ Sand filters have two main pieces: the filter tank and the multiport valve.
➤ The multiport valve controls all operations of the system; this is what determines which
way water moves through the filter tank.
➤ The valve can be installed either on top of the tank—called top-mount—or on the side
of the tank—called side-mount.
➤ Multiport valves are equipped with a sight glass and pressure gauge to aid in regular
cleaning, known as backwashing. The filter should be backwashed when pressure
increases 8-10psi above clean pressure, or the reading on the gauge when the sand is
clean and fresh.
➤ Make sure to always go in the same direction—either clockwise or counter-clockwise—
when changing settings on the multiport valve to prevent uneven wear inside the valve.
➤ Always turn off the pump before changing settings on the valve! Damage can occur if you try to
change settings on the valve while the pump is running.
➤ The tank should be at least half full of filter media but no more than about 2/3 full; this
ensures that water can move through the system—though not too easily—while the sand
traps debris.

5. MULTIPORT VALVE
➤ The multiport valve consists of
the key, cover & handle assembly
and the body. The cover bolts
onto the body; the handle
controls the key, which has a
series of open and closed
chambers.
➤ The key either presses down on,
or has molded into it, the spider
gasket or valve seat gasket. This is
what seals off individual
chambers inside the multiport
valve, allowing water only where
the key & handle are positioned.
Key, cover & handle
assembly
Key
Spider gasket
Body

6. Left: example of multiport valve. Right, top: example of side-mount sand filter,
valve not shown. Right, bottom: example of top-mount sand filter, valve shown.

7. SETTINGS: FILTER
➤ This is the setting that will get the
most use. In this setting, water
returns to the pool.
➤ Water enters through the valve
and goes to the very top of the
filter; pressure from the pump
pushes the water down,
through the sand. Debris is
captured as water is pushed
through the sand.
➤ Water is collected in the
laterals, or fingers, at the
bottom of the unit.
➤ Water then travels up the stand
pipe and back into the pool.

8. SETTINGS: BACKWASH
➤ This setting is frequently used to
relieve an increase in pressure
and remove debris in the filter. In
this setting, water does not
return to the pool and instead
goes out a waste line.
➤ Water enters through the valve
and goes down the stand pipe
and through the laterals.
➤ Water is pushed up through
the sand, grabbing debris
trapped in the sand as it goes.
➤ Water then passes out the
waste line, taking debris with
it.

9. SETTINGS: RINSE
➤ This setting is used after
backwashing to help compact the
sand back into position after
backwashing and to clean out any
remaining dirty water. In this setting,
water travels out the waste line.
➤ Water enters through the valve
and goes to the very top of the
filter; pressure from the pump
pushes the water down, through
the sand to press the sand back
into place.
➤ Water is collected in the laterals at
the bottom of the unit.
➤ Water then travels up the stand
pipe and out the waste line.

10. SETTINGS: WASTE
➤ This setting is used primarily
for vacuuming large debris or
draining out volumes of water.
In this setting, water travels
out the waste line.
➤ Water enters the valve and
travels out the waste line.
Water does not travel
through the sand in this
setting, instead bypassing
the sand, laterals, and stand
pipe.

11. SETTINGS: RECIRCULATE
➤ This setting is little-used in
filter operation; it is primarily
used for troubleshooting to
eliminate or identify the sand
filter as a cause of a leak. In
this setting, water returns to
the pool.
➤ Water enters the valve and
then travels back to the
pool; water does not travel
through the sand, laterals,
or stand pipe.

12. SETTINGS: CLOSED
➤ This is a rarely-used setting on
the filter; water does not travel
out of the multiport valve in
this setting.
➤ Make sure not to leave the
filter on this setting when the
pump is operational; this can
cause damage to equipment.

13. MAINTENANCE & TROUBLESHOOTING: TANK
➤ As previously stated, sand should be backwashed when the pressure increases
8-10psi above normal operation pressure (clean pressure).
➤ Twice a season (or every 6 weeks for commercial pools), sand should be
chemically cleaned using a pool-grade surfactant (Strip Kwik) and/or acid-
based cleaner (Kleen It). These products are generally left to sit in the filter
for several hours to “work;” during this time, the pump should be off.
➤ Chemical cleanings should also happen after treatment of cloudy water, algae,
metals, or chlorine demand.
➤ If a leak is suspected in the sand filter, try running the system on
RECIRCULATE to remove the filter from circulation.
➤ Sand entering the pool is generally a sign of a broken lateral; in the event that
large amounts of sand enter the pool, the stand pipe in the center may be
cracked. Replace at the earliest possibility, taking care to add sand to the unit
slowly to reduce the likelihood of cracking these pieces of equipment.

14. MAINTENANCE & TROUBLESHOOTING: VALVE
➤ The valve seat gasket is usually the first to fail; when this gasket fails,
water will leak into other chambers and flow out the wrong lines.
➤ For valves where the gasket sits in the body, the old gasket can be
removed and a new one installed.
➤ Gaskets should be glued into place using a silicone sealant and left
to cure for 24 hours before operation.
➤ For valves where the gasket is molded into the bottom of the key, the
assembly usually needs to be replaced as these gaskets are non-
repairable.
➤ While replacing just the key is possible, it is not recommended as
disassembly of the key, cover & handle assembly is difficult and
likely to cause other components within the assembly to break.

15. CONGRATULATIONS!
You have completed the activity!