On 07/04/2020 19:10, Chris Hogg wrote:
On Tue, 7 Apr 2020 17:53:31 +0100, Brian Reay wrote:

On 07/04/2020 17:03, Chris Hogg wrote:
On Tue, 7 Apr 2020 14:03:38 +0100, Brian Reay wrote:

On 07/04/2020 13:43, David wrote:
We have been running a water softener for over 7 years now and it does
make a great difference.
The water is soft and shower gel etc. foam easily.

However over time the plug hole of the shower bath has built up a white
deposit.

Has anyone else experienced this?
On line search isn't very helpful.

I assume it may be one of the soluble salts in the water which has become
less soluble and slowly built up, but that somehow doesn't seem right.


I don't run a softener etc but, when I worked in a school in my gap year
pre-Uni, one of my duties was to convert tap water to 'pure' water for
the science lab. The bit of kit use similar to a water softener as I
understand it.

I had to test a sample of the output using a supplied 'kit', if it
failed, the softener needed 'regenerating'

I recall this involved 'flushing' process with something- I can't recall
exactly what- it was 40+ years back- but I seem to recall lab grade
Sodium Chloride was in the mix.

Is there perhaps something in the the softener instructions about
regenerating (or even replacing) the chemicals?

The chemicals in the beast I used looked like tiny, round, cod liver oil
capsules.


Could have been the Permutit process, where water is passed over a
hydrated sodium aluminium silicate, Permutit, and calcium and
magnesium ions in the water are exchanged for sodium ions from the
Permutit. When all the sodium ions had been used up by ion exchange,
the Permutit was regenerated by flushing it with strong brine
solution, when the calcium and magnesium that had been absorbed from
the hard water were displaced and replaced by sodium from the brine,
and the process could then start again.

As the technology developed, the hydrated sodium aluminium silicate
ion-exchanger was replaced by a cationic resin, usually a poly-acid
such as polyacrylic acid, which is your tiny, round, cod liver oil
capsules. They would still have needed to be regenerated at regular
intervals, just like their predecessor, as you describe.

So instead of calcium and magnesium chlorides and sulphates in the
water, making it 'hard', you ended up with sodium sulphate and sodium
chloride in the water, which was 'soft' and didn't make a lot of scum
with soap nor did it fur up kettles etc.

For fully demineralised water, as used in laboratories but not
necessary for domestic purposes, a two-stage resin process was used.
Water was passed over a cation-exchange resin, as above, and the
cations, mostly Ca++ and Mg++, were exchanged for H+ ions on the
resin. In the second stage the water was passed over an
anionic-exchange resin, a poly-amine of some sort, that exchanged
SO4-- and Cl- etc for OH- ions on the resin. The resulting hydrogen
ions and hydroxyl ions from the two resins then combined to give H2O
molecules, and the conductivity of the purified water was extremely
low.

But IIRC the resins had to be returned to the suppliers for
rejuvenating when they became exhausted and the conductivity of the
purified water started to rise.


I can't question your chemistry- it is years since I did any.

As for the rejuvenating process, I remember doing it so perhaps it was
another system. This would have been 1975/6 if that helps.

No, what you described is just what I would expect for the
cationic-exchange resin system, rejuvenated by concentrated brine when
needed. For a school science lab, maybe that's all they needed. At my
school, in the late-1950's and in a hard water area in Surrey, the
school caretaker had the job of regularly flushing with brine the
system that supplied the whole school, but that was before resins
became common so was probably original Permutit.

I think a later development of the 'two separate resin' system, was a
mixture of the two resin beads in a single container, and when
returned to the supplier, they then separated them into the two types
for rejuvenation, possibly by density or by flotation, I don't know.




The system I used was just for the science labs. I used to make a batch
every week or so and store it in containers.