I've been using a French press and emptying the grounds into the sink afterwards The main reason for doing this is that I read somewhere that coffee grounds are a good way to deter pests like cockroaches. I figured washing the used grounds down the drain would keep them from setting up shop in the sink. It only recently occurred to me that this might not be such a good idea and I wanted to know from the more experienced coffee drinkers if I should stop doing this.
You don‘t need the advice of coffee drinkers, you need advice from a plumber (which I am admittedly not, but I have enough contacts in the industry) and a gardener to chime in.
In short: Don’t do it.
Coffee grounds may smell nice and there is that persistent old wives’ tale that will claim that it has [some random positive effect]. It’s not true. Any plumber will tell you that it’s best to pour nothing except liquids down the drains. Coffee grounds are particles that may
- clump together
- collect like sediment in traps
- bind to other fatty residue
- provide food to microorganisms that form that slimy and stinky biofilm in the pipes.
And yes, most plumbers will love you for the habit of washing down your grounds, because it keeps them in business.
Coffee grounds are lovely additions for compost, so either simply add them to your garden compost or treat them like you would any other plant-based kitchen waste.
You may not be a plumber but your advice is sound and I will heed it from here on out. Thank you. Feb 19, 2019 at 18:13
I had read that it was good to put grounds down the drain because the grit helped break up deposits in the pipes. Today we had a $340 plumber bill of to snake out a long run of pipe after cutting out a section to gain access to it. It was totally blocked by an accumulation of coffee grounds that formed a solid plug (needed professional equipment to reach it and clear it). The plumber thanked me for the business, but offered the same advice as this answer. He said it's worse than putting sand down your pipes. Nov 30, 2022 at 0:09
Consider making this thread faq to save people from bad Internet advice. I was going to post a self-answered question to share the experience, and this thread showed up in the similar questions. Nov 30, 2022 at 0:10