How Do I Build a Grease Trap in a Grey Water Line?

Create a trench for the grease trap for your grey water system. It should be deep enough just so the top of the barrel is exposed. Use an 8-degree grade to prevent stagnant water in the system.

Cut the door of the trap out of one-third of a side of the barrel. Add hinges and attach with screws. Also, attach a handle to make the trap accessible. Make sure it fits snugly back into place.

Create the baffles to filter out the grease. Make two baffles out of thin plexiglass. Trim to fit the barrel. Cut a round notch in the bottom of both pieces. Secure them in place using caulk. The placement for these is crucial. The first baffle should go halfway up the barrel and the other should go at the quarter mark in front of the first baffle on the inlet water side.

Cut holes to fit the PVC pipes. Trace the circumference of the pipes to where they go on the barrel and cut out. Secure with caulk. The water from the house should come in on the top of the flat side of the barrel. The output goes in the furthest and lowest part of the opposite side.

Make sure the lid closes securely. An airtight grease trap will prevent pests like mosquitoes finding a home there.

Test the grease trap by running fresh water though it. Look for any leaks and plug them with caulk. Pour some vegetable or other oil into the input. It should float to the surface of the water between the baffles. The output should be clean water. When ready, install into your grey water system.

Create a regular cleaning schedule for the grease trap. Check on it weekly. Skim off the accumulated grease and dispose it.