---
title: "RO Membrane Cleaning Procedure and Chemicals (CIP) | Filtsap"
description: "When to clean an RO membrane, which cleaning chemicals to use for scale, iron, organics and biofouling, and the step-by-step CIP procedure."
source: https://www.filtsap.com/guides/ro-membrane-cleaning-procedure/
updated: 2026-10-23
---

Buyer guide · Updated 23 Oct 2026 · By the Filtsap technical team

# RO membrane cleaning procedure and chemicals

**Short answer** Clean an RO membrane when normalised permeate flow drops 10 to 15 percent, salt passage rises 5 to 10 percent, or pressure drop rises 15 percent from the clean baseline. Use a low-pH clean (citric acid or hydrochloric acid at about pH 2) for scale and iron, and a high-pH clean (caustic at about pH 11 to 12, often with a detergent) for organics and biofouling. Always follow the membrane maker's pH and temperature limits.

## When to clean

Compare today's readings with the readings when the membranes were new or freshly cleaned, corrected for temperature and pressure. Clean when any one of these happens:

- Normalised permeate flow has dropped 10 to 15 percent
- Normalised salt passage has risen 5 to 10 percent (permeate TDS going up on your [TDS meter](https://www.filtsap.com/monitor/water-quality-monitoring/) )
- Pressure drop across a stage has risen 15 percent

Cleaning early works better. A membrane that has lost 30 percent of its flow is much harder to recover.

## Which chemical for which foulant

| Foulant | Signs | Cleaning |
| --- | --- | --- |
| Calcium carbonate scale | Last stage worst, salt passage up | Low pH: citric acid 2% or HCl to pH 2 |
| Iron and metal oxides | Brown deposit, first stage | Low pH: citric acid 2% or sodium hydrosulphite |
| Organics and biofilm | First stage, pressure drop up, slime | High pH: NaOH to pH 11–12, with EDTA or SDS detergent |
| Silt and colloids | First stage, pressure drop up | High pH clean first, then low pH |

When the foulant is unknown, clean at high pH first and then at low pH. Cleaning at low pH first can set organic fouling harder.

## CIP procedure, step by step

- Mix the cleaning solution in the CIP tank with RO permeate, not raw water. Heat it if the membrane allows (often up to 35 to 40 °C).
- Low-flow pump: push the solution into the vessels at low pressure and low flow to displace the feed water. Send the first displaced water to drain.
- Recirculate for 30 to 60 minutes. Check pH and adjust; if the solution changes colour quickly, drain it and mix fresh.
- Soak for 1 to 8 hours for heavy fouling.
- High-flow recirculation for 30 to 60 minutes to flush loosened deposits.
- Rinse with RO permeate until the outlet pH matches the inlet.
- Restart the RO, send the first permeate to drain, and record new baseline readings.

## Prevent the next clean

- Keep SDI below 3 with good pre-treatment. See our [SDI test procedure](https://www.filtsap.com/guides/sdi-test-procedure/) .
- Dose antiscalant with a [chemical dosing pump](https://www.filtsap.com/supply/pumps-valves/) , sized to your water analysis and recovery.
- Change the [5 micron cartridge filter](https://www.filtsap.com/products/pp-spun-filter-cartridge/)  on time: see [when to replace a filter cartridge](https://www.filtsap.com/guides/when-to-replace-filter-cartridge/) .

If membranes no longer recover after cleaning, we supply replacement [RO membranes, pressure vessels and adaptor kits](https://www.filtsap.com/supply/ro-components/) .

## FAQs

How often should RO membranes be cleaned?

Typically every 3 to 12 months, depending on feed water and pre-treatment. Clean when flow drops 10 to 15 percent or salt passage rises 5 to 10 percent.

Which chemical is used for RO membrane cleaning?

Citric acid or hydrochloric acid at low pH for scale and iron, and caustic soda at high pH with a detergent such as EDTA or SDS for organics and biofouling.

Can I clean an RO membrane with raw water?

No. Mix and rinse with RO permeate so the hardness and chlorine in raw water do not re-foul or damage the membrane.

## Not sure what to order?

Send your application and current filter. We reply on WhatsApp.

[Ask an engineer](https://wa.me/918160852169?text=Hello%20Filtsap%2C%20I%20read%20your%20guide%20%22RO%20membrane%20cleaning%20procedure%20and%20chemicals%22%20and%20need%20advice.)  [Request a quote](https://www.filtsap.com/get-quote/)

More guides

- [Filter micron rating guide](https://www.filtsap.com/guides/filter-micron-rating-guide/)
- [Spun vs wound vs pleated filter cartridge](https://www.filtsap.com/guides/spun-vs-wound-vs-pleated-filter-cartridge/)
- [How to choose a bag filter](https://www.filtsap.com/guides/how-to-choose-bag-filter/)
- [When to replace a filter cartridge](https://www.filtsap.com/guides/when-to-replace-filter-cartridge/)

## Need help choosing?

Send your application details and our team will recommend the right filter, at no cost.

[Get a quote](https://www.filtsap.com/get-quote/) [WhatsApp](https://wa.me/918160852169?text=Hello%20Filtsap%2C%20I%20need%20a%20quote.)