Is Citric Acid Safe in a Washing Machine Rinse?
Reddit swears by a spoonful in the softener drawer. One washer maker says it degrades the rubber. What each side rests on, and who should skip it.
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Somebody in r/laundry posted a warning with a title that didn't hedge: citric acid damages washing machines. They'd found Bosch's support page, which says the powder degrades the rubber parts of the machine. A scoop in the fabric-softener drawer, they argued, puts exactly those parts in its way.
The thread didn't take it well. A reply posted the ingredients from the back of the descaler that Bosch's page recommends instead, and the first one is citric acid.
If a laundry thread has sent you out for a bag of food-grade citric acid but your washer's maker has sent you back, here's what each side rests on. It's less than either of them sounds like.
What does the washer maker say?
Bosch's US support page answers one question, whether you can clean the machine with citric acid, and the answer is no. "Citric acid isn't recommended for cleaning your washing machine because it degrades the rubber parts of the machine." It sends you to the Bosch Descaler instead, every few months.
It's about cleaning the machine, a big dose in an empty drum, and it never mentions a rinse dose or the softener drawer. The descaler it recommends lists citric acid first, ahead of maleic acid and a surfactant. Whether that blend is buffered to a gentler acidity, the label doesn't say.
To the thread, that's a maker telling you to keep acid out of its machine and then selling you acid in a bottle for the same machine. One reply called it talking out of both sides of its mouth. The quieter reply is that a bottle can hold citric acid and a buffer, and the two don't behave like the powder on its own.
Will citric acid damage my washing machine?
Hunker's towel guide puts a number on a rinse dose: a teaspoon to a tablespoon during the rinse. The same article says that in high concentrations citric acid can corrode rubber, the seals of a washing machine included. In amounts that small, it says, you shouldn't have a problem.
Back in the thread, the replies make the same argument from the other end. A tablespoon in a rinse doesn't raise the acidity of several gallons of water by much, and the alkaline detergent and the minerals in hard water buffer what's left. Someone else reckoned that if the occasional big cleaning dose did any harm, it would take years.
Then there's the one owner who says it did happen. The person who started the thread found the account in an older thread, under a photo of somebody's drum after a huge cleaning dose:
We tried this a few times, albeit with far less (2tbsp) and over the course of several months it damaged the rubber (maybe silicone?) seal on our wash. It started off as a white discoloring of it, then it slowly started to deteriorate/crack.
u/NoUsual3693, in r/laundry
They had the seal replaced, though it cost them. They can't say why it went wrong for them when so many people use the stuff without trouble. The person whose photo it was put it down to an old or cheap seal, since the synthetic rubber in a typical one isn't bothered by an acid this mild. The dose behind that failure was two tablespoons a load, twice Hunker's top end.
Nobody has run a rinse dose past a seal for years and measured what it did. So what you're weighing is a maker's warning written about a different job, a thread that uses the powder by the spoonful, and one owner who lost a seal.
Who should skip it?
Three cases where the answer is no, or not yet.
- Any load that's also getting chlorine bleach. Bleach and an acid together give off chlorine gas, and Poison Control's rule for vinegar, don't mix it with chlorine bleach, goes for this acid too. Nobody in these threads mixed them. One poster who mentioned using both got shouted at anyway. They'd run them as separate loads.
- A machine whose maker says keep it out. Bosch's warning is about cleaning rather than rinsing, but it's the maker's word about its own rubber. Search your own maker's support pages for citric acid before the first load. If they say the same, that's the answer for your machine, whatever the thread says.
- An old high-efficiency machine that's never had a proper clean. Somebody's first citric acid rinse, in a machine at a house they were clearing, let loose a smell so bad they thought the sewer had backed up. The thread's best guess was years of fabric softener and dryer-sheet residue coming off the drum, and the poster came round to that. A reply added that if there's sulfur in the water, citric acid can liberate it. The smell faded with each load, so it's a warning about the first few loads rather than a reason never to start.
Start with the maker's page. One that doesn't mention citric acid, and a machine that's had a cleaning cycle now and then, leave you with the thread's own practice.
That's a teaspoon to a tablespoon of food-grade citric acid in the rinse, and bleach in a different load. Old machine? Open the laundry-room door before the first load.
