How to Get Rid of Drain Flies

Those tiny, fuzzy little flies hanging around the sink or shower are drain flies, and they are not coming from your rubbish or your fruit bowl. They are breeding in the slimy gunk inside your drain. The only way to get rid of drain flies for good is to clean out what they are feeding on. Here is how.

What drain flies are

Drain flies (also called moth flies or sink flies) are small grey-brown insects that breed in the film of organic gunk, the biofilm, that lines a slow or dirty drain. They lay their eggs in it and the larvae feed on it. Spray all you like, but as long as that food source is there, more will hatch. Kill the breeding ground and they disappear.

Confirm it is the drain

Quick test: tape a piece of clear sticky tape over the drain opening overnight, sticky side down, leaving a small gap for air. If flies are breeding in that drain, you will find some stuck to the tape in the morning. It tells you which drain to target.

How to get rid of them

1. Clean out the drain. Remove the grate and scrub inside the pipe opening with a bottle brush to break up the biofilm they breed in. This is the most important step.
2. Bicarb, salt and vinegar. Pour half a cup of bicarb soda and half a cup of salt down the drain, follow with a cup of white vinegar, and leave it overnight. Flush with hot water in the morning.
3. Hot water flush. A kettle of hot water (not boiling on PVC pipes) once a day for a week helps wash out the larvae.
4. Avoid the caustic cleaners, they do not reach the biofilm coating the pipe walls where the flies actually breed.

Keep it up for a week or so to catch the full breeding cycle.

When it signals something bigger

Stubborn drain flies that keep coming back, even after a good clean, usually mean there is a thick build-up further down the line than you can reach, or a partial blockage where waste is sitting and rotting. The same gunk that causes the flies also causes smelly drains and slow drainage.

If you have cleaned the drain and the flies keep returning, the breeding ground is deeper in the pipe. A high-pressure jetter scours the whole line clean and takes the food source with it. If you are in Newcastle and the flies will not quit, give us a call and we will clear out what is feeding them.