Tech Talk - Water Filters
EnviroSpec’s Technical Library
Section: General Information
Inlet Water Filters
A pressure washer should never be operated with an unfiltered inlet water source. Components in the machine can be severely damaged by just one piece of grit flowing in with the supply water. The different types of water filters commonly used on pressure washers include hose washer screens, bowl type filters, and y-type filters. Important features of a water filter are physical size, PSI rating, temperature rating, screen mesh size, port size, flow rating, and ease of servicing. Filter inspection and cleaning should be part of your equipment maintenance schedule. A dirty filter starves the pressure washer for water, which adversely affects performance and causes pump failure. Filters should be routinely checked weekly. When a flow or pressure loss is experienced, the filter is one of the components to be examined for problems.
Section: Flow Rating
Adequate flow is crucial to the operation of the pressure washer. We recommend using a water filter that has a flow rating twice the requirements of the pump. So a 5 GPM pump would require a 10 GPM flow rated water filter. If you make the pump work trying to pull water through a restricted water source you pump maintenance increases dramatically. The type of water source that is used effects the rated flow of a filter. Using a pressurized feed, like a municipal or well supply, pushes more water through the filter than working off a tank feed that is creating little or no PSI. Most filters are rated for both a pressurized and suction flow rate. If a filter is rated for only pressurized flow, it probably shouldn’t be used in a water tank application.
Section: Physical Size
The dimensions of a water filter are important because number one it has to fit in the space where it is being installed into the inlet port of the high-pressure pump, and number two, if the filter is very small it limits the size of the filtering mesh surface. The less surface that is available to filter out debris, the quicker that surface will get dirty and begin to inhibit the water flow. A washer filter, for example is used very commonly on pressure washer equipment. It has an extremely small mesh area that clogs rapidly, and it also isn’t visible. Both these features combine to create a situation where the inlet water flow is likely to become restricted, a condition that is very detrimental to the pump. Ideally, the larger the mesh surfaces the better. If the space for a filter at the pump is limiting you to a small size, consider mounting the filter remotely and running another section of hose from the filter to the pump inlet.
Section: Port Size
The larger the inlet and outlet port size is the easier the water can flow through.
Section: PSI Rating
Inlet water filters are installed on the low-pressure side of the pump. The source water pressure must not exceed the PSI rating of the filter however. Most inlet water filters are rated to withstand 125 to 150 PSI. If the inlet water supply exceeds the rated limits of the filter most of the time it will blow out the gasket or crack the filter bowl. If the inlet supply pressure is too high for the filter, it is also to high for the pump, and a pressure-reducing valve should be installed upstream from the filter. Water tank applications have either very low PSI created by head pressure, or operate with suction in the feed line, so the PSI rating of the filter is unimportant. One other point is when the unloader bypass line is routed directly to the water filter the pressure of the by-pass water can become problematic if it is being forced through a small opening. If this is the case, route the by-pass to the water tank, or to the pump inlet on the opposite side from the water filter. Increasing the by-pass line ID reduces the PSI produced by the by-pass flow.
Section: Screen Mesh Size
80-mesh size screen for an inlet filter is considered to be standard. For higher volume pumps, a larger mesh is advisable, 40 to 60 mesh being appropriate. The higher the number, the smaller the openings in the mesh are. Other mesh sizes are also available. The smaller the opening in the mesh, the greater the filtration, unfortunately the smaller mesh also clogs up quicker and it creates a greater resistance for the water flowing through it. This in turn reduces the gallons of water that will be able to flow through it in a given amount of time. A larger mesh reduces resistance but does not filter out particles that are too small.
Schedule inspection and cleaning weekly. A y-trap type filter has a clean out that can be unscrewed on the lower section of the y. This is where the pollutants that have been filtered out collect. Flush the trap and the screen then reassemble. When cleaning a bowl type filter unscrew the bowl from the filter body, flush the bowl and the filter, then reassemble. Hand-tighten the bowl, tightening further will crush the washer and create problems in the future. Always be careful when reassembling to seat the gasket properly and to not cross-thread and damage the threads. A clear bowl water filter allows for inspection without disassembly. While the filter is disassembled inspect the mesh screen and replace the filter is damage is discovered. If using a hose washer filter, which isn’t recommended, clean the filter mesh screen daily.
Section: Temperature Rating
This is only a factor if you use a supply source with hot water. Very few operations do so, as hot water affects other components of the pressure washer also. If you run equipment that has high temperature packings in the pump, and all the other components are rated for high temperatures, then you also have to check the rating of the water filter. Typically poly or nylon filters are rated at around 120 degrees. Aluminum filters are rated a high temperatures, up around 190 degrees.