Cartridge filters require manual cleaning on a regular basis.
Most manufacturers recommend cleaning cartridges when the filter pressure rises 8-10 pounds above the start up/clean pressure. However, some filter's pressure won't go up even when the filter elements are filthy so... most pool professionals in Arizona recommend manually cleaning cartridge filters once every six months. After a few cleanings, you'll learn more about the pool and how dirty the filter is becoming and can vary the cleaning intervals.
Here are a few pictures from a recent filter cleaning job completed in Mesa, Arizona.
The manual cleaning process takes somewhere between an hour and two hours depending on how dirty the filter is, how many elements are being cleaned, and how large the elements are.
When a pool has been green for a long time - more than 6 months - the interior is coated with a green algae slime that is often crusted onto the pool interior. To remove it, you can complete a pressure wash, acid wash, or chlorine bath. In most cases, an initial pressure wash removes most of the algae slime. I'm posting photos of a recent job showing an interior pressure wash and the results.
Pool is drained... and stained.
The spa is pretty dirty too!
Beginning to pressure wash.
And more washing...
And still more pressure washing...inch by inch. This job took us about three hours.
Acid washing a pool is a procedure to apply a diluted acid mixture to pool plaster striping away dirty and stained plaster. Because the process removes a layer of the plaster it isn't something that should be done every year but rather two to three times during the normal life of the plaster which is typically about 15 years.
Pool is drained here and ready to be cleaned.
Note the staining on the walls...
Touching up some spots with a fine grit sand paper.