On Fri, 8 Feb 2019 14:56:14 +0000 (GMT+00:00), "Jim K.."
wrote:

Archibald Tarquin Blenkinsopp Wrote
in message:
On Fri, 8 Feb 2019 13:00:55 +0000, (Roger Hayter)
wrote:

Just a note for the procurement department. I have a 'Zilmet' Italian
made *potable water* 25 litre expansion tank that has been in use for
four years, and is full of rust, including fair-sized rust flakes. Our
water is from the mains and somewhat soft but nothing out of the
ordinary.

So I know what not to buy. Anyone any recommendations?

Check the pH of the water.

High or low pH produces rust?

Oxygen produces rust, low pH strips away the initial film enabling the
O2 to act with vigour.

Is the tank being fed from a local
authourity supply or are you pumping from a well?

If you want to keep using the tank bung some phosphoric acid into it.
Your local waterworks should be doing it anyway if they are feeding
any older properties.

to do what?

The initial film of phosphate coats the surface, it is more difficult
to remove, so further oxidation is prevented. Many Morris Marina
owners would dispute this, but a none Leyland driver would be fully
aware of the benefits.


AB