Some washing machine manufacturers advise against connecting their washing machine to an full artificially softened water supply (not the electronic water "conditioners" mentioned above) as it can make the water too soft for washing. If you don't reduce the amount of detergent it can result in over-sudsing, but less detergent can give poorer wash results.
Modern washing machine detergents can be less effective in very soft water because the detergent does not dissolve as well. This can cause detergent deposits on laundry.
Summary: Using a washing machine with an artificially softened water supply should not damage the washing machine, but wash results can be affected due to the detergent not dissolving properly and leaving detergent residue on laundry. This may be counteracted a little by using an extra rinse option on the washing machine if available. This advice may also help If you live in a (naturally) very soft water area. My current understanding is that this advice is relevant to chemically softened water rather than electronically conditioned devices mentioned above, which claim to condition the water and prevent limescale build up rather than physically soften water.
Related: Should I use Calgon anti limescale tablets or other such products?
If anyone knows any different I’ll be glad to amend my advice on this subject.
Do your research. Don't waste money with bad purchases. 
Interesting, I’m sure this will surprise many people who fit softeners in the sole belief it is better for their machine and cheaper in detergent than using hard water. Hard mains it is then (for now). Another aspect to consider were you to consider going down the softened route is the pressure loss through a softener (this can easily be 1bar) which may then leave you with insufficient pressure at the machine.
Thanks Neil: I think the intended advantage of a water softener on the entire water supply is to combat limescale in the immersion heater, hot taps, kettles, coffee makers & showers etc and not white goods appliances which should be protected by their detergent.
Many water softeners use ion exchange, where sodium ions replace calcium & magnesium ions to soften the water. The effect of increased sodium going into the washer may result in agressive reactions with metalic items such as the drum, shaft and spider eventually leading to premature mechanical failure.
I agree with Bob above, nearly all the probs I have come across on drum shaft spiders ( I’m working mostly on a german brand who have well constructed drums) have occured where the machine is connected to a water softner (using salt – not magnetic, electrical) and in most cases they have had low usage i.e an older couple, no kids doing 1 -3 loads a week .
My theory is this; the softening is achieved by exchanging calcium and magnesium ions with sodium ions. When you start to wash with this and add chemical alkilis (detergent) and heat you get a fairly agrresive solution which starts to degrade the metal especially the shaft spider alloys. Then they don’t use the machine for say 4 days, and in the meantime the residue water starts to evaporate leaving a much stronger solid residue probably high in Sodium which is an alkaline metal and a very reactive metal ( back to chemistry lessons) which continues to do the damage at an increasing rate.
With higher usage it appears to be less of a problem as the water never really evaporates off , as it’s in fairly constant use and also if it does happen after say 12 years of heavy use would you worry about it? possibly not.
I would advise it’s better to steer clear of these types of softners on a washing machine and just use the correct amount of detergent that is good quality and you should be fine as Andy says. You could also employ a ‘one shot’ descaler ands use it once or twice a year and is would still be cheaper than the big brand descaler that we’re asked to use every wash.
I’ve been using water-softeners since 1984, and supplying my dishwasher and washing machine from them. The washing mnachine was replaced a few weeks ago due to motor failure, after 28 years of use. It had never gone wrong otherwise, and has always been free of limescale and soap deposits. The clothes come out clean and the towels and other items are soft and fluffy (which you can’t say for towels washed in hard water).
I have seen no evidence of ill-effects from softened water.
Thanks for your contribution John. Using a washing machine with an artificially softened water supply should not damage the washing machine, but wash results can be affected due to the detergent not dissolving properly and leaving detergent residue on laundry although it seems you have noticed no issues.
I don’t understand why you say the detergent might not dissolve properly. I find everything dissolves better in softened water, so it doesn’t leave soap scum in the bathroom, for example, and it cleans away existing soap residue. Also you need less detergent. Have you seen any independent scientific tests on soap powder and softened water that I can look at?
Hi John. I was quoting from washing machine manufacturer’s advice on the subject. Detergent already has sufficient water softener built into it, so if you use the correct amount of detergent combined with already softened water, the water can be too soft. Detergent can over foam creating too many suds. This will cushion clothes from each other and potentially reduce cleaning efficiency.
The problems with dissolving would presumably be if the water was too soft rather than just being soft, so maybe you get the combination of not all the detergent dissolving properly but the detergent that does dissolve creates too many soap suds.
If you reduce the amount of detergent used (and don’t go on what they recommend) then you may not have any problems.
Been using a water softener for 5 years now with all of the house taps including the washing machine and dishwasher.
Depends on the powder that you are using as to how well it dissolves, e.g. main brands are OK, but Aldi brand tends to clog in the soap drawer. But I’m not sure if this is to do with hard or soft water, or the quality of the powder.
Definitely follow the instructions on the powder pack as if you live in a soft water area. Do not over-dose. In fact, I tend to underdose slightly. I never noticed any effect on the quality of the wash, apart from the clothes feeling softer. Also cut down on the amount of fabric softener you use – only half the dose, mainly to add a nice smell to the final rinse.
Liquid washing machine detergent is better still – no powder residue at all.
Also, I never put salt into the dishwasher any more. The washing tablets don’t soften the water – the salt fill does that, but it’s not needed if the water supplying it is already softened.
Dreadfully harsh towels coming out of machine since softener fitted. Wd vinegar in the rinse help? Can’t use “less detergent” – the capsules are one size.
Hello Rob, it could be detergent residue as detergent doesn’t dissolve easily in very soft water. Make sure you reduce the amount of detergent used to that recommended for soft water. You could also try selecting extra rinse option if available or making sure you don’t use eco wash cycles that might use less water and make rinsing less effective. As a last resort you could try doing a few extra rinses.
Alex- thanks for the chemistry input. I have that precise type of ion exchange- which removes pretty much all minerals (because I need to remove iron). The problem is ever since the filter, the clothes are getting ruined. I have since turned off the polyphosphate additive, knowing this is a ‘sequesterer’ of what, i’m not sure, but the purpose is to deposit scale on pipes to avoid corrosion.
My laundry is better, fewer tears, but things are stretched and weak. I have now just started adding magnesium sulfate and by gosh I see a difference. They come out less crunched (wrinkled absurdly) and feel a tad bit sturdier. I want to also try calcite- so basically I am trying to turn the water into what it was before, less the iron.
I am also assuming the calcite (gypsum) will absorb some of those excess salts, which may be softening my fabrics too much. Do you think this last one will be a mistake? (calcite) I don’t want calcium deposits or anything that will damage the washing machine. I just want balanced water.
I finally did find some research stating that these precise minerals are used in the industry to give body and stability to fabrics. Just what they need to endure the spin cycle.
I have yet to try re-shrinking those stretched out lifeless clothes with hot water and a hair dryer / or pellet stove. I’m afraid IT will stress the fibers. Will have to test. As it is my sleeves are well over my hands and sweaters are limp and baggie, PEOPLE ARE OUT OF THEIR MINDS TO WANT SOFT CLOTHES- SOFT WATER !!!!!!!
(thanks to whitegoodshelp for these helpful articles/comments)
Thanks Kathi. And thanks also to Alex’s comment from a few years back. It looks like I might have missed it before.
Just had new machine & dishwasher put in but the kitchen fitter didn’t connect them through the new Softner seen limescale build up in dishwasher already so do I use Calgon or get it connected to Softner? Don’t want my machines ruined as really hard water here in herts! Our last water Softner was used with machines & no limescale problem?
Hello S. I have a separate article linked to at the end of this article, which you should read. Essentially if you use the right amount of detergent and ensure that is good quality detergent then you should not need any other water softener. It might not hurt to use Calgon. If you do use Calgon you are supposed to reduce the amount of normal detergent to the dose for soft water. As far as I can see it’s the main function of Calgon because essentially it is only doing what the detergent already does. So the main point of using Calgon as far as I’ve been able to work out, is so that you can use less detergent. I’m unsure if the combination of limescale tablets and less detergent would be cheaper or more expensive than using the highest dose of detergent for hard water or not. Probably not is my guess but I don’t know if anyone’s ever worked out the maths.
Here is the article, Is Calgon Worth Using?