When any of the Aquatron stills have been used to produce distilled water directly from a mains water supply, there will inevitably be a build-up of scale in the boiler and on the heating element(s). To obtain optimum performance from the still the scale should be removed on a regular basis. The time span between cleaning depends entirely upon the hardness of the water supply. In very hard water areas it may be necessary to clean the still once a week, whereas in soft water areas several weeks may elapse before cleaning is necessary.
It should not, of course, be necessary to de-scale the second stage boiler on the A4000D or when the stills have been operated from a de-ioniser. Cleaning the still involves the use of concentrated hydrochloric acid. As a safety precaution protective clothing, gloves,mask and goggles should be worn during cleaning.
The cabinet and perspex screen should be cleaned using a dilute detergent solution only.
It is possible to descale the Aquatron Water Still without dismantling the glassware by following these instructions in conjunction with Control of Substances Hazardous to Health regulations (COSHH) 1988.
1 Push the CLEAN switch to the CLEAN position – the switch illuminates.
2 Observe that the heating element/s has switched off. Allow boiling to stop and water to cool.
3 Push ON/OFF switch to OFF position.
4 Remove perspex screen.
5 Open the Rotaflo stopcock on the level control WL48, allow the boiler to empty to 3/4’s of its full capacity, and close stopcock.
6 Carefully add about 100ml. of concentrated hydrochloric acid into the glass funnel of the WL48.
7 Push the ON/OFF switch to the ON position, the boiler will refill to its operating level.
8 Push the ON/OFF switch to the OFF position.
9 Allow the chemical reaction within the boiler to continue until all the deposits have been removed.
Note – if scale has built up above the operating level, the boiler may be completely filled by either lifting the drain pipe or restricting the flow of water to drain. This operation must be carefully controlled so that the boiler does not over-fill and cause water to be forced over the funnel top.
10 Open Rotaflo stopcock and allow contents of the boiler to drain completely.
Note: If the acid added to the boiler has not been completely neutralised, the liquid flowing to drain may be
strongly acid. Necessary safety precautions should be observed around the drain position, and any effluent control procedures followed.
11 Close Rotaflo stopcock.
12 Push ON/OFF switch to ON position and allow boiler to fill with water. Again the boiler may be completely
filled by following procedure detailed in step 8.
13 Push ON/OFF switch to OFF position.
14 Drain the boiler by opening the Rotaflo stopcock.
15 Repeat steps 11-14 two or three times until the boiler has been thoroughly flushed through.
16 The still is re-started by finishing the cleaning cycle at step 12, and then pushing the CLEAN switch to the OFF position. (Switch is not illuminated). Before collecting the distillate the still should be allowed to run for about 10 minutes with the distillate running to drain, this will ensure that any residual acid is removed.
Note: The amount of acid required will depend upon the degree of scaling. If after performing the cleaning cycle deposits are left in the boiler, it may be necessary to repeat the cleaning cycle using a fresh quantity of acid. The benefits gained from regular cleaning cannot be over emphasised