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Removing precipitate in hydroponics system


When 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:

Step 1.  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).

Step 2. 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.

Step 3. Afterwards, neutralize the flushing solution to pH 5 6 with soda ash before discarding.

Step 4. 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 above 5.0.

Step 5. 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 click here.


** 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.


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Related topics:

"System & plant maintenance":

General hygiene | Discarding old nutrient solution | Flushing root zone | Nutrient disinfection | Nutrient deficiency symptoms

Disease control | Pest (insect) control | Pruning | Plant support | System clean-up between crops | Foliar Fertilizers