How To Change Medium In Backwashing Water Filter

How Backwashing Filters Work

Backwashing h2o filters are large tank-manner filters that get their name from the fact that they clean and renew themselves by backwashing. Backwashing consists of reversing the flow of water then that it enters from the bottom of the filter bed, lifts and rinses the bed, then exits through the top of the filter tank.

The filter bed itself is a granular substance that is usually referred to as the filter medium. Media (media is plural, medium is singular) are numerous and varied. Mutual media are granular carbon, sand, garnet, anthracite, zeolite, granular manganese dioxide, and greensand. Many media are known by their make names of the leading production in the category: Centaur, Filox, Birm, Filter Ag, and KDF, for example.

The picture at right shows the filter in "service" position. This is how it works when it is doing the job it is designed to do. The unfiltered h2o enters from the left and is routed by the control valve into the filter tank. The water then filters slowly through the medium until information technology reaches the bottom of the tank where it is nerveless through a particularly-designed sieved "basket" at the bottom of the eye tube seen in the picture. The filtered water and then passes up through the center tube, called a "riser" or a "dip tube," passes through the command valve, and exits the right side of the filter.

Notation that there's a drain line in the picture, but no h2o goes through it during the filter'south "service" function.

The Backwash

As the filter operates in the service mode, it traps and holds particles in the filter bed. Also, since water's nature is to follow the path of least resistance, subsequently a time it begins to cut channels through the medium. As channels or holes in the media bed grade, water begins to menses around rather than through the medium. This process is chosen "channeling," and it tin can reduce the effectiveness of the filter considerably.

At a preset fourth dimension, the control valve initiates a "aftermath" to make clean the medium of collected particles and to resettle the bed and eliminate channels that have formed.

The backwash is accomplished by sending water down the riser tube from which it enters the filter tank at the bottom. The force of the water is such that it actually lifts the media bed, swirling and tossing the granular medium. The water leaves the filter tank through the control valve, which routes information technology through the filter'southward drain line. Particles that were being held in the bed are washed to drain.

The backwash is an intense rinsing and tossing of the medium that lasts for several minutes. In a standard residential filter, a typical backwash lasts about ten minutes.

After the aftermath, the command valve initiates a "rinse" of the bed during which h2o flows downwards through the medium, up through the riser tube, and out the drain. The purpose of this rinse is to rinse and settle the bed and gear up information technology for render to service flow.

Incidentals about Backwashing Filters

Tanks. Called "mineral tanks," nigh are made of polypropylene and/or polyethylene with fiberglass reinforcement. Mineral tanks are very strong and commonly guaranteed for up to ten years by the manufacturer.

Control Valves. Almost modern filters use timer-style controls in which an electric timer initiates and controls the backwash of the filter at a pre selected time. Meters, which backwash the media when a certain number of gallons take been treated, are used widely on water softeners only much less ofttimes on filters. Some very sophisticated setups tin can initiate backwash in response to a pressure differential betwixt the incoming and approachable water, but for most situations, the standard, reliable timer control is preferred on backwashing filters.

Media. With a few minor modifications, a backwashing filter can serve many dissimilar purposes co-ordinate to the filter medium used. Here are some of the more than mutual granular media used in backwashing filters:

Granular Activated Carbon. For chlorine and chloramine reduction, sense of taste/odour comeback, general chemical reduction. Carbon tin too remove sediment and even iron if the iron is pretreated properly. It is the most commonly used medium for hydrogen sulfide reduction. Granular carbon is the preferred treatment for many chemical contaminants. Information technology is maybe the nearly versatile and universal of filter media.

Birm. For reduction of iron and manganese, under the right weather condition. Every bit iron media get, Birm is relatively light in weight and hence easy to backwash. It is besides depression in toll, so it'southward a popular iron medium although information technology has some drawbacks. A pH of at least six.eight is ordinarily required for Birm to remove iron.

Calcite. To increase the pH of acidic water. Calcite is a sacrificial medium that dissolves equally it works and has to exist replaced.

Centaur Catalytic Carbon. Reduction of chlorine, chloramine, hydrogen sulfide, and iron. A relatively expensive grade of specially prepared carbon, Centaur is a favorite for chloramine removal on city h2o systems.

Multi-Media, consisting of layers of such natural elements as garnet, sand, and anthracite: Used for the reduction of sediment and oxidized iron, multi-media filters are slowly being replaced past newer granular zeolite media.

Filter Ag, Zeolite, Micro Z. These are all common "sediment" media. They reduce particles in water down to xx to 5 microns. These are usually natural zeolite products.

Greensand. Reduction of iron and hydrogen sulfide. Greensand is usually used with a potassium permanganate feeder.

Filox. A natural mined mineral, Filox is known for loftier level iron removal and reduction of hydrogen sulfide odors. Information technology is very dense and requires frequent and intense backwashing.

Backwash Rate. Aftermath flow rates differ significantly from filter to filter.The correct backflow rate is essential to proper operation of a backwashing filter.The correct backwash flow rate is determined by because the square footage of the surface of the media bed and the density of the media. The filter must take a flow control installed in the drain line to let a aftermath flow rate sufficient to raise and cleanse the media bed merely restrictive enough to prevent media from beingness washed out the bleed line. For case, a carbon bed in a 10" Ten 54" filter tank is usually installed with a five gallon-per-minute flow restrictor. V GPM is sufficient to lift and clean the bed, but carbon is dense enough that it will not exist washed out of the drain line during backwash. By dissimilarity, KDF, a very dense medium, requires a aftermath of more than 15 GPM in the same filter.

Service Flow. Service flow of the filter is limited by the size of the tank and the nature of the medium. Some media require longer to piece of work than others. Media are rated according to the service flow they tin support by a measurement called "empty bed contact time" in filter-maker jargon. When the recommended contact time for the medium is violated by excess service flow, the filter is less constructive and the life of the medium is usually shortened. Information technology should be noted that empty bed contact fourth dimension requirements are oft violated in residential filters. For case, filter carbon in a ten" X 54" filter has a performance limit of nigh iii gallons per infinitesimal, but such filters are frequently used in residential applications with much higher catamenia rates. There is no slap-up impairment in this since the undersized filter removes most of the chlorine most of the time. However, if the same filter is used to reduce dangerous organic chemicals from well water, its upper service flow rate should be limited to mayhap i GPM, and exceeding this limit could take serious consequences.