Quick Answer
Plan a branched drain system by identifying branches, pipe sizes, and material, considering the flow rate and slope of each branch, and designing for easy maintenance and future expansion.
Identifying Branches and Pipe Sizes
When designing a branched greywater drain system, start by identifying the different branches and their respective pipe sizes. A good rule of thumb is to use separate branches for showers, sinks, and washing machines, and to route each branch to a separate drain field. Use a minimum pipe diameter of 1-1/2 inches (38 mm) for each branch, and consider using PVC or HDPE pipes for their durability and resistance to corrosion.
Slope and Flow Rate Considerations
Ensure that each branch has a minimum slope of 1-2% to prevent siphoning and stagnation. Calculate the flow rate for each branch using the estimated water usage per fixture, and consider the flow rate when selecting the pipe diameter. As a general rule, a 1-1/2 inch pipe can handle a flow rate of up to 2 gallons per minute (GPM).
Designing for Maintenance and Expansion
Design the branched drain system with easy maintenance in mind. Use accessible clean-outs and tee fittings to allow for easy inspection and cleaning of each branch. Also, leave room for future expansion by installing additional branches and drain fields as needed. Consider using a mainline pipe with a minimum diameter of 2 inches (50 mm) to connect the branches, and ensure that the mainline pipe is properly sized to handle the total flow rate of the system.
Find more answers
Browse the full Q&A library by topic, or jump back to the topic this question belongs to.