Sand Vs Cartridge Filtration Systems
We undertook a deep dive into the pro’s and con’s of two of the most popular swimming pool filtration methods based on residential pool usage which are often debated amongst pool builders and pool owners.
The following information in general in nature and based off the experience of a swimming pool builder covering the installation, repair and maintenance of both sand and cartridge filters over approximately 15 years.
Sand filters - are a common type of filtration system used to keep swimming pools clean. They work by using a filter media, typically made of sand, crushed glass or a similar material, to trap dirt, debris, and other contaminants present in the water.
When water is pumped through the filter, it enters the filter tank and passes through the sand media. The sand acts as a physical barrier, trapping particles that are larger than the spaces between the sand grains. As water flows through the sand, it is forced to pass through the filter media, which removes dirt, debris, and other contaminants.
The sand filter also has a backwash valve that allows the filter to be cleaned. When the filter becomes clogged with dirt and debris, the client will open the backwash valve, reversing the flow of water. This causes the pool water to flow in the opposite direction which pushes the dirt and debris out of the filter. The backwash water is then discharged through a waste line into the sewer system, removing the contaminants from the pool. The back washing process is very easy if all components are in good working order and takes approximately just 4 minutes.
Sand filters are effective in removing larger particles such as dirt, debris, and even algae from the water. They are also relatively low maintenance, as the sand only needs to be replaced every 5-7 years. The filter typically only needs to be backwashed/cleaned every 4 weeks. Sand filters come in numerous sizes and in very basic terms the bigger the filter the better.
However, sand filters do have some limitations. They are not as effective at removing smaller particles and they can also be less energy efficient and less water efficient than other types of filters. Sand filters also have what is called a multi port valve (MPV) that has moving/mechanical parts with rubber seals which can leak pool water out of the system, leak dirt/dust/debris and sand back into the pool costing money and causing frustration.
The multi port valve is rather easy to service and maintain however experience tells me once the sand is due for a change at 5-7 years old, the MPV is on its last legs. The MPV has internals that when turned to backwash the filter can wear and cause issues. The turning function can cause sand or similar rough particles to lodge between the mechanism and the housing so when (not if but WHEN) the MPV starts leaking water out of the backwash line down the sewer pipe or starts leaking dirty water from the filter back into the pool then the only option is replacement as new rubber seals wont stop the leaking water from escaping from the worn housing.
Sand filters also have ‘Laterals’ at the base of the filter underneath the sand which are plastic tubes with fine gaps/slots to allow the clean water to pass though back into the pool. These laterals can distort, have debris lodged in the fine openings or can crack and break allowing sand/dirt/dust/debris to constantly flow back into the pool. These laterals are not easy to access or repair as the sand needs to be removed from the filter to access the laterals.
With the above mentioned issues many pool companies have adopted the practice of each sand change also replace the MPV and laterals in the base of the filter also, in order to reduce costly issues in the near future.
Overall, sand filters are a reliable, cost-effective up to the 5-7 year mark, and low-maintenance option for keeping swimming pools clean. They work by using a granular filter media to trap dirt and debris, and have a backwash valve that allows for easy cleaning. While they may have some limitations, they are an effective and widely used method of pool filtration.
Cartridge filters - are a type of filtration system used to keep swimming pools clean using a filter cartridge made of pleated polyester or polypropylene material to trap dirt, debris, and other contaminants present in the water.
When water is pumped through the filter, it enters the filter tank and passes through the cartridge. The pleated design of the filter cartridge increases the filtration surface area and allows the filter to capture smaller particles than a sand filter. As water flows through the filter, it is forced to pass through the filter pleats, which removes dirt, debris, and other contaminants.
The filter cartridges are easily replaceable and typically last between 8-10 years if cared for. They can be easily removed and cleaned or replaced with a new cartridge. Unlike sand filters, which require backwashing, cartridge filters are cleaned with a garden hose, which is still a simple task however a little more time consuming. Cleaning frequency depends on the size of the cartridge filter, correctly sized cartridge filters only required cleaning every 4-6 months depending on the usage of the pool. Smaller cartridge filters may require cleaning weekly.
Cartridge filters are very effective in removing smaller particles such as dirt, debris, bacteria, and even some viruses from the water. They also have a longer media lifespan compared to sand filters, and are more energy-efficient as they require less water to clean the filters than a backwash as well as not using pool water to clean the cartridges, saving on chemical usage.
However, cartridge filters do have some short falls also. They can be more labour intensive when required to clean the cartridges and may require tools to open the filter for cleaning or replacement. If the filter is under sized the constant need to clean the cartridge can become bothersome in comparison to an undersized sand filter needing constant backwashing.
Overall, cartridge filters are a convenient and very efficient option for swimming pool filtration. They work by using a filter cartridge to trap dirt and debris and have a replaceable and easy to clean design with no mechanical parts. They are effective in removing smaller particles and the filter element has a longer lifespan than the media in sand filters when sized correctly.
|
CASE STUDY |
CA400 Sand Filter |
QL540 Cartridge Filter |
|
Filters debris particles down to |
20-30 Microns |
8-12 Mircons |
|
Filtration surface area |
0.46m2 |
50m2 |
|
Life of filter media |
5-7 Years |
8-10 Years |
|
Max water flow (According to manufactures brochures) |
144,000 ltrs per 6 hours |
180,000ltrs per 6 hours |
|
Yearly water usage to clean filter based off recommended cleaning frequency |
Backwash every 4 weeks for 3 minutes, Rinse for 1 minute. 300lp/m pump = 14,400l p/y |
Hose cartridges every 4 months for 20 minutes. 60lp/m from tap. 3,600l p/y |
|
Chemicals lost from filter cleaning. |
Salt 50kg, Alkalinity 4kg, Stabiliser 1kg, Pool Acid 2.5ltrs, Chlorine 48 hours of run time. |
None |
|
Mechanical parts to suffer wear and tare |
Multi port valve (MPV) |
None |
|
Cost to run over 10 years |
Filter tank 1253.79 Glass media 478.40 Sand change 1100 MPV replacement 381 Water 169.62 (Assuming 50% of water loss is re filled by rain) Lost chemicals 1058.80(Standard Salt) 2763.80(Mineral Salt)
Total $4441.61 (Standard Salt) $6146.61 (Mineral Salt) |
Filter and cartridges 2929.89
Cartridge replacement 1221.44 Water 57.50 (Usage from tap)
Total - $4198.83
|
|
Tools required to clean filter |
None |
1 |
|
Time over 12 months to clean filters |
48minutes |
60minutes |
Conclusion when comparing Sand VS Cartridge filter of a similar size -
Sand filters -
Pros’s
- Quicker and no tools required to clean then the cartridge filter.
Con’s
- Cleaning required more frequently (Monthly)
- Cleaning requires much more water wastage
- Cleaning uses pool water which in turn wastes pool chemicals which can can be very costly for mineral pools
- Sand changes are difficult
- Multiport valves always fail over time causing issues such as dirty pools and leaking pool water into sewer line
- Filter laterals are difficult to access if/when needed to repair
Cartridge filters -
Pro’s
- Filter out 3x finer particles which reduces chemical usage and pump running time.
- Have a far larger surface area filtering out particles quicker, reducing pump running time to maintain clarity and clear dirty water.
- Have longer lasting filter media.
- Simple design making replacement of filter elements simple, quick and easy
- Can allow higher water volume through the filter when required for spa jets/water features ect.
- Require far less water to clean the filters saving on water bills or water tank usage.
- Uses only tap water to clean filters instead of pool water, eliminating chemical wastage through backwashing out expensive chemicals such as mineral pool salt.
- Have no moving/mechanical parts to wear and tear.
- Are cheaper to run over 10 years and continue saving money each year after.
- 100x larger surface area for filtering quicker.
Con’s
- Cleaning the filters every 4 months takes approximately an extra 12 minutes per year then the time to back wash a sand filter 12 times per year.
- May require a tools to open the filter
At Conquest Pools Albury Wodonga we strictly install quad cartridge filters on residential pools due to being far superior in water filtration, water consumption and energy efficiency as well as saving money in every aspect of your swimming pool. On top of the high efficiency and money saving, the water quality is also superior which has the added benefit of when there is a high bather load or ever an event where a lot of dirt/dust/debris enters the pool then a quad cartridge filter has a surface area 100x that of the similar sized sand filter meaning the dirt/dust/debris is filtered out far quicker allowing for a cleaner pool in drastically less time.
Is there a use case for sand filters? Yes. But for the average residential swimming pool…….. Rarely, if at.
Phone: 0260592405
www.conquestpoolsalburywodonga.com