However, a newer challenge has presented itself now that variable-speed pumps (VSPs) have become extremely prevalent on today’s pools.
“In the past it was simple, the pump was either on or off, and you just took the filter pressure measurement,” says Dan Lenz, a manager at All Seasons Pools in Illinois. “However, now that the pump is not on at full flow all the time, it becomes harder to get an accurate pressure reading because as flow increases, pressure increases and not necessarily because of a dirty filter.”
As VSPs do not constantly operate at full speed, it makes it harder to obtain an accurate filter pressure reading. To overcome this issue, many service techs turn up the pump to the highest pre-set circulation speed (not the highest speed on the pump) and take a pressure reading during their weekly service.
Those techs who are not doing a weekly service should ask their customers to perform this task and tell them to call the pool service company if their filter pressure increases by more than 4.5 kg (10 lb). Running the pump at the highest pre-set circulation speed and checking filter pressure is part of the weekly service routine, along with cleaning the pump baskets, skimmers, etc.
Cleaning the filters when there is a large change in pressure is especially important with cartridge and DE filters as it can prolong the life of the filter. Following this procedure will also help to avoid compression and compaction of dirt and debris on the face of the DE grids and/or cartridges, making them last longer and easier to clean.
“In the past, it was common to keep an eye on the filter pressure reading. If there was an increase of 11.3 kg (25 lb), it was time to backwash or clean the filter,” says Lenz. “However, now with cartridge filters, cleaning the media when there is a 2.26-kg (5-lb) pressure increase is recommended. Sticking to this rule of thumb will help to prolong the life of the client’s filter. If a tech waits for a 4.5-kg (10-lb) change in pressure, the pleats will begin to collapse and the bands will start to break.”
Richard Deakin, a certified pool operator (CPO), certified pool instructor (CPI), and commercial product development manager at Hollandia Pool & Spa in London, Ont., says filter backwashing is very site specific, which poses several variables that need to be taken into consideration before backwashing, as well as determining the length of the backwash cycle.
“Industry standards state a sand media filter with single gauge should be backwashed when the pressure increases between eight and 10 psi from its starting setting. Dual gauge filters have an industry standard of a pressure differential of 10 to 20 psi,” he says. “That said, most operators backwash filters on routine, not on demand, which is counterintuitive to the functionality of these types of filters. My advice, however, is to get to know your system and its limitations, and work within those limits.”
Automatic controllers can be invaluable when it comes to knowing when to backwash a dirty filter. Rather than having a tech perform weekly manual checks, the automation system can be set to backwash the filter based on its pressure readings. Pool professionals who truly understand the filter/pump relationship can incorporate these best practices for cleaning into their winterizing routines and help their customers achieve clean and clear water in the spring.
