Water softener efficiency

[wookey]

We live in an extremely hard-water area and as part of the great renovation are considering getting a water softener to stop the new hot water tank going the way of the old one (uselessly caked heat exchanger) and just generally not having limescale on everything.

What I'm struggling to find good info on is how much salt they use per litre of delivered soft water, how much electricity they use and how much water they use for flushing. Also which machines/features give better efficiency in this regard.

Blurbs are full of useless bollocks like '"50% less salt usage" (than what?) and "20 Euro cost" (over what period and why not tell me the kWh which is what I actually wanted to know) etc.

The one thing I did learn that was useful was that a counter-current flush uses less water than a with-current flush (because it doesn't contaminate clean resin at the far end of the canister, which then needs some more flushing).

We have very low water usage of about 34l per day on average (2 people) so a small one should be fine. Does size affect efficiency at all? Presumably you need a minimum size in order to have a useful flow rate for shower/filling bath?

I'm looking at salt ion-exchange softeners here. I'm assuming that all the dubious electronic/magnetic water treatment things probably don't workvery well, and if they do they only reduce scaling in some fairly short period of time after the water passes through so aren't going to work very well in a hot water tank for a low-usage water tank where the water might be in there for a couple of weeks before getting used. And you still get limescale on taps/sinks/etc.

Any advice on who makes the better kit is welcome.

[HML]

Electricity use should be minimal; some of them use water flow to power the regeneration counter but even if they use an ordinary timer the power used will be 1-2W.

Salt use will be proportional to the hardness of the water and the amount of water softened. Timed regeneration might use a bit more salt than water quantity metered regeneration, but the difference isn't likely to be much if the timed periods are set up sensibly. In terms of efficiency of the softening process I doubt that there's any difference. There are very few makers of the resin units; all the manufacturers will use the same ones. If you're concerned about running costs get one that uses granular salt rather than block salt. It's cheaper, if slightly less convenient. Dual unit models are sold on the basis that they will always give a supply of softened water, however, if you set a timed unit to regenerate in the early hours of the morning (or whenever you're not about if you're nocturnal) the lack of softened water will be imperceptible. A short period of unsoftened water isn't going to do anyharm even if it does regenerate while your using water.

In our last house, with very hard water, I used the cheapest timed unit I could find easily (branded Pemutit from B &Q although they don't seem to stock them any more). It worked perfectly well while we were there. I'll do the same here when I get round to it although I might pay a bit more and get a metered one.

I don't think the magnetic ones work at all, but it's easy to persuade yourself that they're doing something.

[wookey]

Thanks for that.

Timed regeneration might use a bit more salt than water quantity metered regeneration, but the difference isn't likely to be much if the timed periods are set up sensibly

I just talked to a supplier and found that their machine flushes (uses 72l) every 2280l or 6 days whichever comes first. We typically use 32 l/day so use about 200 litres in 6 days, not 2000, so it will run exclusively on the timer. This will essentially add 23% to our annual water usage which seems very inefficient. Turns out that only costs about 12 quid so not the end of the world but I hadn't realised just how much water these things use, and that they are not well-suited to frugal water users. And 90% of our salt usage is going to be wasted.

I don't know if anyone uses a longer period, or if there are resins suited to less frequent flushes.

A short period of unsoftened water isn't going to do anyharm even if it does regenerate while your using water.

Indeed we've survived 30 years without it. Do you get hard water during regeneration or no water (on the softened supply)?

[wookey]

I just discovered there is a 3rd sort of softener: citrus-based, which adds citric acid to reduce the Ph and chelate your calcium and magnesium compounds. Mr Risinger of 'Build Show' fame likes his:
The disadvantage is you need their fancy cartridge at $150/throw, not plain salt. and they want to sell you one every 6 months, although I wonder if that can be extended for us low-usage types or if something actually expires. '20,000 gallons' would be about 6 years for us. As you can measure the pH you can probably check whether it is still working or not...
Made by an outfit called NuvoH2o : https://nuvoh2o.com/

Anyone heard of citrus water softeners before? Seems a bit more believable than the electronic ones, but this field seems prone to bullshitters.

[HML]

A short period of unsoftened water isn't going to do anyharm even if it does regenerate while your using water.

Indeed we've survived 30 years without it. Do you get hard water during regeneration or no water (on the softened supply)?

Yes. The softener is bypassed during regeneration.

Don't know about the one in the youtube video but you used to be able to get polyphosphate dosing devices which I believe reduce scale, although they aren't softeners. They're still going https://www.combimate.co.uk/. Mind you, at that price you might as well get a proper ion exchange softener, unless the slight extra plumbing for the drain is a problem.

[Oliver90owner]

Is that 34l/day hot water? Temporary or permanent hard water? Only temporary hardness causes scale due to the dissolved Calcium hydrogen carbonate being converted to insoluble carbonate at about 85 Celsius.

One would need an expensive low energy density immersion to avoid/reduce the scale formed. They are much longer, for the same Wattage, so the energy density is much lower. Likely need to be across the cylinder rather than vertical, too.

There should be no scale in a hot water cylinder if heated to a sufficiently low temperature by an indirect central heating boiler.

The scale produced is crazy if using the typical electric immersion heater. The surface temperature is sufficient to drop out the carbonate and any that sticks to the element will exacerbate the problem.

I expect that solar thermal panels would reach a sufficient temperature to deposit scale.

Have you thought of a thermal store to heat your meagre hot water requirements?

[robl]

Our Monarch 7E water softener is plumbed into the dhw feed, which does hot and cold shower water, none of the hot taps. I think they still make a similar ‘midi’ model. We use around 150l/day of water all in, estimating half of that softened.
The softener has an ac/ac old school transformer pregnant plug that runs annoyingly hot, and takes 4.8W all the time. I think it regenerates around once a week, using a kg or so of salt and maybe 100litres of water. Bit of guessing - I measured the power, but not water flow, and the salt goes in 10kg at a time. I buy 10x10kg bags in a go, I think it lasts a couple or three years maybe.
From our figures, I reckon it uses around 10% of our water use.
I expect you need the smallest available unit, and one that has a flow meter to ensure it doesn’t regenerate before it needs to.

[tony]

I like twin cylinder non electric, minimises salt use and uses no electricity, regenerates when water meter says to switching to other cylinder and regenerates exhausted one ready for next swap

[greentangerine]

I like twin cylinder non electric, minimises salt use and uses no electricity, regenerates when water meter says to switching to other cylinder and regenerates exhausted one ready for next swap

I have a twin cylinder Kinetico. Totally clockwork and now the children have left home, the salt blocks last about a month or slightly longer which means about £5 now the prices have gone up.

Have had it for over 20 years and still working fine. We have very hard water here and wouldn't be without it.

If I forget to replace the blocks, the kettle starts to scale immediately and you can feel the difference in the water when showering.

[tony]

In my opinion you should not be drinking artificially softened water