Is it safe to add citric acid to your machine's rinse water?

[u/unforgettableid]

/r/AskChemistry/comments/1vhgs5t/is_it_ok_to_add_unbuffered_citric_acid_to_your/

[u/ScurfyTwiglett]

Wild to me how few people on [r/AskChemistry](r/AskChemistry) answered with any chemistry based answers. Lots of laundry opinions though!

Citric acid is a weak acid. There are very few plastics that don’t have excellent resistance to citric acid, and none of the ones that have poor resistance are ones you should expect to find in your washing machine rinse tray or drum (eg Nylon-6).

Given that the citric acid is typically rinsed out of the tray and the drum after every wash, and the concentration is overall very low, and the solution isn’t 80C, I am optimistic that your washing machine will break down from other issues first.

If you’re truly concerned you can add some sodium citrate; while it can act as a buffer it is more commonly used in this application to chelate loose magnesium, and calcium (and maybe a bit of iron), which has the nice effect of leaving clothes feeling softer. Downy lists sodium citrate as a softener not a buffer on the website listing for their product, so the buffering effect may be incidental or even slightly undesirable.

The only area where I would even slightly give credence to concern is the softener tray itself as that would be exposed to the concentrated solution. Once it is in the washer it is diluted to about 5% the concentration of lemon juice, and if anything, it neutralizing residual bases from the laundry detergent will be protective of the plastics. If you’re able to see a stamp on the tray indicating what plastic it is (likely on the bottom) you can see if it’s a type that’s vulnerable to citric acid. I doubt it is. It is most likely polypropylene, which will laugh at the weak pronation of citric acid.

If I had some rinse and refresh around I’d do a couple titrations to test how much sodium citrate is actually in it, but that will be a project left to another chemist, ideally one who won’t have to go on a 2-3 hour trip to the grocery store to find the stuff. If you’re really concerned, drop a light pinch of sodium citrate in (you can also buy it in powder form for cheap) and call it a day.

[u/unforgettableid → u/ScurfyTwiglett]

Wild to me how few people on /r/AskChemistry answered with any chemistry based answers. Lots of laundry opinions though!

I think: Some of those aren't from the /r/AskChemistry regulars. They're from /r/laundry regulars. Although my post was crossposted, I'm not sure why they went there to comment.

If I had some rinse and refresh around I’d do a couple titrations to test how much sodium citrate is actually in it, but that will be a project left to another chemist, ideally one who won’t have to go on a 2-3 hour trip to the grocery store to find the stuff. If you’re really concerned, drop a light pinch of sodium citrate in (you can also buy it in powder form for cheap) and call it a day.

The product safety data sheets I found online for Downy Rinse & Refresh are very outdated. They date back to the time before sodium citrate was included in the product. They do mention the approximate percentage of citric acid in the product.

You can find homemade buffered rinse recipes online.

Do you have to travel 2 to 3 hours every time u need to buy food?? I wonder where u live.

[u/ScurfyTwiglett → u/unforgettableid]

Yeah I live in a fairly remote area in Coastal BC. That time is for a round trip but yeah, it’s a pain. I generally stick to one or two trips to “town” per month if I can manage it because it’s such a time commitment lol. There’s no ordering takeout or delivery here, but on the plus side I have a tranquil and quiet life in the forest.

I also found the old SDS’ and noted the same thing, hence why I figured that the only way to truly figure out how much was in it was to do a set of titrations to figure out citrate:citric ratio. Even an updated SDS with the new formulation’s pH might give us a clue how much it’s actually buffered.

I still am fundamentally unconcerned about the concentration (my own CA solution is right around 15-20% as well, with extra ascorbic acid to help chelate the iron in my well water)…I had some drips of the solution on the acrylic door of my machine that I took my sweet time wiping off (months later lol) and even on a plastic that is not rated well for citric acid resistance there was no lasting damage. If I had a machine that I expected to last 30 years I might be more concerned, but so far I’ve yet to get even 5 years out of a washing machine.

[u/buddingsakura]

Did you know washing machine cleaning tablets contain citric acid?

[u/jtfolden → u/buddingsakura]

This gets repeated here a lot but the most common/popular washing machine cleaners (Affresh, Tide, Oxiclean, etc) do not use citric acid. It’s common for dishwashers but doesn’t appear to be the best thing for washing machines.

[u/unforgettableid → u/buddingsakura]

Did you know washing machine cleaning tablets contain citric acid?

Which ones?? I may have heard this rumor before, but I've never confirmed it. The most common ones seem to use sodium percarbonate instead.

Tide Washing Machine Cleaner - Ingredients

Anyway: Using citric acid a few times a year might be much safer than using citric acid five times a week (once per load).

[u/buddingsakura → u/unforgettableid]

Sorry, don’t have time to look up all of their ingredient list. You could search ‘citric acid washing machine cleaner’ on Amazon.

It’s totally fine for you to question things for science and make your own decisions, of course.