Filter System

Filter System


Single-Family Model RWAF (Automatic Filter) Package (store)

Our Systems:

ReWater filter installation in a vault—greywater irrigation mode

ReWater filter installation in a vault—backwash mode

Filter System Installation Video

The operative principle of all our systems is the same  – we use greywater (shower, tub, bathroom sink, laundry water, RO tail water, etc.) as it is produced, keeping that water highly oxygenated and thus good for plant life, and keeping the filter systems and downstream piping and tubing relatively free of clogging due to aerobic and anaerobic growth.  Our process also minimizes the space required for a filter system, which minimizes the cost of that filter system and the property required to house it.

The difference between our pre-engineered filter units is in the size of the surge tank, size of piping connecting to it, pump pressure and capacity, and filter vessel flow rating.  Almost all single-family residences use one of our two basic models, either the RWF2, RWAF2 or RWAF3 (the “A” is for “automatic”).  The model RWF2 and RWAF2 have 2″ piping connections and can handle the water from up to 4 showers, tubs, and/or laundry drains, i.e., “fixtures” without overflowing to the sanitary sewer. The RWAF3 has 3″ piping connections and can handle up to approximately 17 fixtures.  For commercial sized systems, our RWAF4 and larger listed systems have larger piping connections as required for your application.

When selecting a filter system for a single-family residence, choose a tank, pump, and filter that can handle the potential maximum surge from your combined water sources, or you may periodically lose high-peak-surge water to the overflow.  As an example, if you have 5 regularly-used showers that can each produce 2.5 gallons of water per minute (GPM) and a clothes washer that can produce 12.5 GPM but only for two minutes, your maximum surge is 25 GPM over two minutes when all those fixtures are in simultaneous use.  Our standard 120 VAC pump distributes 50 GPM at level elevation with good irrigation pressure, when enough emitters are downstream to omit that volume, so our standard 70 gallon tank can usually handle that 50 gallon surge with our standard pump and filter vessel.  See the chart below for some standard pump flows, using 40 feet of head as the minimum required pressure on level property.

Single-family sized pumps are 120 VAC single phase, even our ultra-high pressure model.  208 VAC single phase and 220 VAC single phase filter systems are standard on larger systems and require the correct controller.

Note 1: All automation is provided by a ReWater controller, which needs 120 VAC.  A controller is included in all irrigation packages; its size depends on your needs. When ordering your irrigation package, we must know your pump’s electrical requirement, as the controller’s relay must be the correct voltage for that pump. For a 208 – 230 VAC pump, you need our NEMA 4 pump relay junction box for your pump’s voltage.

Note 2: For lifting water above the tank/pump location and for long irrigation runs, we need to calculate the TDH required to determine the correct pump, which could be 208 – 230 VAC.


For multi-family, commercial, and institutional systems, the most common high surge is usually a more cost-effective design target than the maximum surge potential from the building.  For example, in a 100 unit apartment building capable of producing 125 GPM from showers and 50 GPM from lavatories, for a total possible surge of 175 GPM, the most common high surge will occur in the hours of 6:30 – 7:30 a.m., when many people shower right before going to work.  The “most common” surge considers that, while many people shower at night and use bathroom sinks in the evening hours too, the total surge occurs over a wider range of hours, thus the need for a much larger tank is diminished.  Many other factors such as lift and distance, and soil type and plant selection, come into play when designing larger filters and their accompanying irrigation systems.  ReWater regularly consults on the design, engineering, and construction of greywater irrigation systems and can do so for you.

How a ReWater filter system operates:

When pump (L) turns on because float switch (M) rises in water in tank (A) during the irrigation cycle, water is sent to the top of filter canister (I) and forced down through the 20 grit sand filter media, where hair, lint, and other debris is trapped in tiny spaces between the sand particles. Water then travels out to a series of irrigation valves for use in the yard.  Larger systems have larger surge tanks and pumps, but act on the same principle of using water as it is produced, instead of storing it.  This keeps the water fresh and oxygenated, which is good for plants.  Our controller starts and stops based on water availability, and our filter is backwashed with fresh water based on accumulated run-time.


Filter systems do not come fully assembled, as the plumbing design is different in each home.  The schematic shown is for illustration purposes only.

To keep the filter clean, when the controller has accumulated a certain (programmable) amount of run time, it begins a self-cleaning cycle after that day’s irrigation has been completed.

At the end of the day’s irrigation cycle, the controller begins the self-cleaning cycle by opening valve (J) to let city water in and rotating valve (H) to divert the backwash to waste. City water is then rapidly forced up into the 20 grit sand filter media, causing sand particles to rise and separate from each other, releasing the trapped debris. Lighter than the sand, the debris rises to the top and flows out to the waste line.

When the process is over, the valves return to their irrigation position. This cleaning process has been used in agriculture, swimming pools, and water purification for decades.

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