sidewall deposits become significant, they can harbour disease and also
cause blockages if present in plumbing lines.
An acid flush can be effective for removing
precipitates of salts such as calcium sulfate (Fig 12.4). These
generally cannot be dissolved with plain water or wet brushing:
Add water and enough hydrochloric
acid** to the reservoir to achieve pH 2. If using rain or RO water, dilute
30% hydrochloric acid (normal commercial strength) by around one-thousand
fold i.e. 1ml per litre (3/4 tsp per Gal).
Soak the system for 24 – 72 hours. While the system is soaking:
- Recirculating systems: Run the pump for at
least 15 minutes in every hour.
- Run-to-waste systems: Run the pump for a
short burst once every hour and collect the discharge.
Afterwards, neutralize the flushing solution to pH 5 – 6 with soda ash
Flush the whole system several times with fresh water to remove all traces
of acid and dislodged material. Ensure the pH of the final washings is
Where fine drippers and sprayers are used, it may be necessary to
individually dismantle and clean each unit.
For details on how to
sterilize hydroponic systems
Avoid contact with metal parts and ensure to follow necessary safety
precautions. Use protective clothing (e.g. mask, goggles, gloves).
30% hydrochloric acid is volatile (emits significant fumes)
therefore decant in the open air. Also, because this chemical is
highly volatile and corrosive, store it in a well ventilated area.