Don't Jilt The Filter: Choosing The Best Filter For A Lawn Sprinkler System
Posted on: 9 May 2016
A efficient sprinkler system relies on many components to function effectively, but one that is perhaps overlooked is the water filter. Contrary to popular belief, filters are not only a requirement for agricultural-scale irrigation systems -- whether your sprinklers draw water from the mains or from collected rainwater, detritus and sediment from unfiltered water can build up in delicate moving parts and drastically shorten the lifespan of your system.
Fortunately, small-scale filters for lawn sprinkler systems are readily available. However, there are several different kinds of filter to choose from, each with their own advantages and disadvantages, so make sure the filter you choose can effectively service your needs.
Media filters
These simple filters contain a fine, abrasive material (usually specially ground filter sand) that catches solid detritus and particulate matter while allowing water through. An excellent choice for small, low maintenance filter systems, media filters are generally inexpensive and easy to install, and require little maintenance beyond occasional inspections for leaks and physical damage.
However, while media filters are effective when it comes to removing solid debris, they cannot filter out microscopic contaminants such as bacteria, pollution and algal spores that can infect and damage your lawn. As such, they may not be suitable for sprinkler systems drawing water from rainwater collection tanks, particularly in urban areas prone to acid rain. The physical resistant provided by the solid media also results in a drop in water pressure, which can cause problems with low-flow systems.
Screen filters
Essentially similar to a scaled up coffee filter, the porous screens contained within these filters catch particulate matter in the same way media filters do. However, screen filters tend to be much more compact, and the simple screens are far easier to remove and replace than large quantities of sand. They also result in less pressure loss, although low pressure systems may still struggle against an oversized filter.
To offset these advantages, screen filters require more maintenance than media filters, and screens require cleaning and/or changing regularly during the dry summer months. Screen filters are also more fragile than other filter types, and while they can stand up to regular, timed sprinkler use with no problems, constant usage can cause them to fail rapidly.
Disc filters
These filters function on the same principles as screen filters, but exchange the single screen for an array of interlocking screens that provides effective filtering of much smaller particles. Consequently disc filters are capable of filtering out small organic contaminants such as algae, and are excellent choices for use with rainwater-fed sprinkler systems.
However, the large number of screens contained within a disc system magnifies the potential problems a disc filter can cause, and the heavy physical resistance can cause serious water pressure problems when used with underpowered or overpowered pumps. Disc filters are also more complicated to clean and maintain than single screen filters, and purchasing replacement discs can be expensive.
Centrifugal filters
Unlike other systems, centrifugal systems do not rely on physical filters to remove debris. Instead, the water that passes through a centrifugal filter is spun at high speed, resulting in heavier particulate matter being drawn to the edges of the filter by centrifugal force, where it is removed. As such, a centrifugal filter in good working order requires little to no oversight, and avoids the extra expenses of purchasing screens or filter media.
Unfortunately, these cost savings can be offset by the costs of powering your filter, although some centrifugal filters can be effectively powered by small solar arrays. In addition, the air pockets created within the filter by centrifugal forces can cause dramatic pressure loss, especially if your filter is too large for the water supply you have available.
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