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Plumbing Overview

Plumbing and graywater codes vary substantially from one state to the next, even from county to county.

The IrriGRAY collection & pumping system has been designed to overcome these challenges by being a flexible product that is constructed on site to suit local codes. In addition to reducing the cost of the manufactured product , our experience is that plumbing installation costs are reduced by 25-40%.

Basic Principles

Every graywater collection  container must have at least 1 inlet & 1 overflow to sewer or septic. The overflow pipe must be at least the same size as the inlet pipe (or combination of inlet pipes, as more than 1 inlet pipe can be used if this simplifies the plumbing process).


Because of the significant variations between states regarding sewer backflow prevention, a backflow valve is not included with IrriGRAY systems. Consult your local plumber for recommendations.

Graywater Diversion Valve

If graywater irrigation is not required (during  a wet winter), or desired (bathrooms are being cleaned with non garden safe checmicals), simply turn off the power supply to the IrriGRAY system.

The unique design of IrriGRAY systems allows the container to empty without using the pump.

Some jurisdictions may still require installation of a graywater diversion valve before the container, due to specific code requirments.

Graywater stubout height vs sewer pipe height

Where possible, design the drainage plumbing so that the graywater stubout is at least 14" above the sewer pipe level.

This allows the container to drain completely to sewer without using the pump - a requirement is some jurisdictions.

The lower drains are not required in some states (eg Arizona), in which case the inlet pipe can be just an inch or so higher than the sewer pipe.


By using trickle valves, the IrriGRAY collection container does not require electronic controllers nor water sensors. This enables affordable system pricing without compromising pump quality, the key to system longevity and return on investment.

Inlet / Overflow Pipe Sizes

Any schedule 40 ABS or PVC pipes up to 4" can be connected to the IrriGRAY container.

The standard size is 2" - if other sizes are required additional seals (special order) will be required.

Selecting the right size IrriGRAY container

300' of IrriGRAY dripperline will irrigate at between 8 and 10 gallons per minute. This is faster than graywater is generated in most houses. Therefore, the storage capacity of the container does not matter.

The most important size factor is how deep the graywater stubout/s are below natural ground level.  If the stubout/s are above ground level, the 20 gallon above / partial inground container is best. If the stubouts are located below ground either the 18" x 22", or 18" x 30" container wil be required. Refer to the product description for more information.

Which graywater sources?

Acceptable graywater sources for the garden include shower, bath, laundry and lavatory (basin) water. Blackwater (kitchen water not passing through a grease trap, and toilet water) is not acceptable.

Due to the small amount of graywater produced by basins, it is often uneconomical to connect these sources. In many cases builders prefer not connecting basins as the small amount of water is useful for ensuring enough water is passed through the blackwater system to flush the waste pipes within the house.