CIP cleaners — acidic or alkaline, and when to use each
Short answer: Use an acidic cleaner for mineral scale and iron deposits, and an alkaline cleaner for organic matter, biofilm and colloidal fouling. Where both are present, always clean alkaline first — acid applied over organic fouling can set the deposit and make it harder to remove.
Identifying the fouling first
The symptoms tell you which cleaner you need:
| Symptom | Likely fouling | Cleaner |
|---|---|---|
| Flow down, pressure up, hard feed water | Mineral scale | Acidic |
| Pressure drop across housing rising | Biofilm or organic | Alkaline |
| Reddish or brown deposits | Iron oxides | Acidic |
| Slimy feel, sometimes odour | Biological growth | Alkaline |
| Gradual decline, poor SDI feed | Colloidal or silt | Alkaline |
| Uncertain | Mixed | Alkaline then acidic |
What the acidic cleaner does
It dissolves mineral deposits — calcium carbonate, calcium sulphate and metal oxides — by lowering the pH so those salts return to solution.
Best for:
- Calcium carbonate scale, the most common on Indian borewell water
- Iron and manganese deposits
- Plants where antiscalant dosing has been interrupted
See our ZeroScale acidic membrane cleaner.
What the alkaline cleaner does
It works differently — rather than dissolving minerals, it lifts and disperses organic matter, biofilm and colloidal particles, using surfactants and chelating agents.
Best for:
- Biofilm and bacterial growth
- Organic fouling from surface water
- Colloidal and silt fouling
- Oil and grease traces
See our ZeroScale alkaline membrane cleaner.
Why sequence matters
Concentration and pH
Follow the product instructions rather than guessing. Two rules apply regardless:
- Stay within the membrane pH limits — these are on the membrane datasheet and exceeding them causes permanent damage
- Mix with permeate water, never raw water, which would introduce the very salts you are trying to remove
Monitor pH during circulation. If it drifts significantly, the cleaner is being consumed and may need topping up.
Temperature
Warm solution cleans considerably better than cold — but only up to the membrane temperature limit. Exceeding it damages the membrane permanently, so check the datasheet before heating.
The cleaning procedure
The full step by step method is in our CIP cleaning guide. The essentials are:
- Record readings before cleaning
- Flush with permeate
- Circulate at low pressure and higher flow
- Soak for 30 to 60 minutes — this does much of the work
- Circulate again
- Flush thoroughly
- Record readings and compare
Safety
- Gloves, eye protection and apron every time
- Add chemical to water, never water to chemical
- Never mix acidic and alkaline cleaners — flush thoroughly between stages
- Store them separately and label clearly
- Ensure ventilation and have clean water available
What to do between stages
When running both cleaners, flush completely with permeate between them until the pH returns to neutral. Residual alkaline meeting fresh acid produces heat and neutralises both, wasting the chemical and achieving nothing.
If cleaning does not work
| Result | What it means |
|---|---|
| Little improvement | Wrong cleaner chosen, or fouling too advanced |
| Flow improved, rejection not | Membrane ageing alongside fouling |
| Rejection worse after cleaning | Possible pH or temperature damage |
| Improves then declines quickly | The underlying cause is still present |
That last case is the important one — if performance falls again within weeks, the problem is upstream. Check antiscalant dosing, pre-filtration and recovery. See our membrane life guide.
Preventing the need
Frequent cleaning is a symptom. On a well run plant CIP should be needed once or twice a year. If you are cleaning quarterly, fixing the upstream cause will save both chemical and membrane life.
Need CIP chemicals?
Describe the symptoms and your feed water, and we will recommend the correct cleaner and sequence.
💬 WhatsApp par poochhein 📞 9910646957Frequently asked questions
When should I use an acidic cleaner rather than alkaline?
Acidic for mineral scale and iron deposits, where flow has fallen and pressure risen on hard feed water. Alkaline for organic matter, biofilm and colloidal fouling, which typically shows as rising pressure drop across the housing.
Why must alkaline cleaning come before acidic?
Organic material often sits on top of mineral scale. Applying acid first attacks the scale underneath while the organic layer remains, and acid can coagulate organic matter into a harder deposit.
What water should cleaning solution be mixed with?
Permeate water, never raw water. Mixing with raw water introduces the very salts you are trying to remove, which reduces the effectiveness of the cleaning.
Can acidic and alkaline cleaners be mixed?
Never. They neutralise each other and generate heat. When running both stages, flush completely with permeate between them until the pH returns to neutral.
What if cleaning improves performance but it declines again quickly?
The underlying cause is still present. Check antiscalant dosing, pre-filtration and recovery settings. Frequent cleaning is a symptom of an upstream problem rather than a solution in itself.