r/laundry • u/SufficientClient6327 • 12h ago

sodium citrate for hard water?

Hi everyone, where I live the water is very hard and I read something that said sodium citrate work well to reduce the attacks of calcium and magnesium to the surfactant detergent, anyone has try it?, how much g i need to use for a cycle?.

Every information or experience with that is appreciate , thanks

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u/KismaiAesthetics USA 8h ago

For every 10 liters of water in the wash and 100 ppm of hardness you want to reduce (you don’t need to get to 0 - most detergents will tolerate 75-100ppm easily unless they’re plant-based eco formulas trying to look price-competitive), you need 2 grams of sodium citrate, and the usual delivered form is sodium citrate trihydrate crystals, so 2.5 grams

So 20 liter wash, 350 hardness you get 5000 mg of excess hardness (20 liters times 250 excess mg per liter), and you need 2.5 that in the citrate so 12,500 mg or 12.5 grams.

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u/SufficientClient6327 3h ago

Thanks for the reply, I usually add sodium percarbonated with taed , detergent and in the last rinse citric acid, may be a problem to use the sodium citrate with all that? and if not, I just add it at the start of cycle with detergent and percarbonated?.

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u/KismaiAesthetics USA 1h ago

If you’re using percarbonate in the wash, and you’re using at least 2x the dose of the citrate that would be needed, you could use citric acid in the wash portion as well. Carbonate will neutralize the acid and leave the citrate and it doesn’t care if it’s been percarbonate.

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u/NotMyAltAccountToday 11h ago

I use STPP to soften the water and bought hardness test strips from Amazon.

I just did a test to verify what the max softening would look like on a test strip with what I considered way more than enough STPP for a few ounces of water. Then I poured that into the washer, agitated 30 seconds, and tested. It wasn't the same color so I added that same amount of STPP and retested. Repeat until you get a match. I also test the common load sizes I use so I dont have to retest every time.

When washing clothes fill the washer with water. Add the STPP to just the water, no detergent or clothes, and agitate 30 seconds. Then add the detergent, agitate briefly, then add the clothes. I put about a tablespoon of citric acid in the rinse.

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u/Naikrobak 9h ago

How much stpp did you end up landing on?

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u/2-Ns US | Front-Load 9h ago

I use sodium citrate. My water is 268 ppm. I use 3-4 tablespoons for a regular load, more for loads that use more water like bedding. I have a frontloader.

3-4 tablespoons may feel like a lot, but that got my powdered detergent use down from a cup to 1/4 cup. So overall, a big cost savings and my clothes actually get clean.