Pick the Sanitiser for the Job and the Hardware
Sanitisers in hydroponics have two very different roles: keeping recirculating solution biologically stable, and disinfecting structures, media and equipment between cycles. A product that is excellent at the second can be damaging in the first, and the same chemistry behaves differently depending on pH, organic load, temperature and what your pipes are made of.
This guide compares the three products most commercial farms end up shortlisting — peracetic acid, hydrogen peroxide and chlorine dioxide — on the things that decide the outcome: what they kill, what they corrode, how you control the dose, and what they cost to run safely.
The Three Compared
| Factor | Peracetic acid | Hydrogen peroxide | Chlorine dioxide |
|---|---|---|---|
| Mode | Strong oxidiser; effective over a wide pH range | Oxidiser; releases oxygen as it breaks down | Oxidiser; generated on site or from activated precursors |
| Organic load sensitivity | Moderate; less affected than chlorine | Reduced effectiveness where organic matter is high | Reasonable tolerance; still consumes on demand |
| Breakdown products | Acetic acid, oxygen, water | Water and oxygen | Chlorite and chloride residues depending on conditions |
| Materials | Corrosive to some metals; check seals and fittings | Oxidising; check elastomers and metals | Corrosive to metals in concentrated form; ventilation and generation controls needed |
| Handling | Pungent; requires PPE and careful dosing | Irritant; strong solutions hazardous | Requires trained handling, particularly where generated on site |
| Typical use | System disinfection, line cleaning, between-cycle treatment | Routine recirculating control and root-zone oxygenation at low rates | Disinfection of water and surfaces, including treatment of source water |
No column wins outright. The right answer depends on whether you are treating solution in a loop with plants in it, or stripping a structure down between crops.
In-Crop: What You Can Use While Plants Are Present
This is the most constrained case, because the product has to be active against pathogens and safe for roots at the same time.
- Dose to a measured residual, not to a recipe. In-crop use lives or dies on monitoring
- Start low and confirm plant tolerance on a small block before dosing an entire loop
- Watch root appearance and growth rate for several days after any change
- Do not use sanitiser to hide a root problem. Where disease pressure is high, fix oxygen, temperature and hygiene first
- Confirm compatibility with filters, membranes and any biologicals in use — including beneficial microbes
Between Cycles: Stripping Down
Here higher concentrations are acceptable, contact time can be controlled, and the target includes biofilm on internal surfaces.
- Remove organic matter first. No sanitiser works well through a film of debris — cleaning precedes disinfection
- Choose the chemistry for the surfaces present: channel, media, tank, PPE, tooling
- Fill the system fully so contact includes pipe interiors, not just the visible surfaces
- Hold the required contact time and verify rather than assume
- Rinse where required and dispose of used solution according to local rules
- Record what was used, at what concentration, and for how long — audit-ready records are cheap when written at the time
Materials Compatibility
| Material | Watch out for | Practical step |
|---|---|---|
| Carbon steel and poorer stainless grades | Corrosion from oxidisers, especially at joints | Specify suitable grades for hardware in contact with dosed water |
| Copper and brass fittings | Oxidation and dissolution | Avoid in dosed circuits where possible |
| Elastomers and seals | Hardening, swelling, loss of seal | Confirm elastomer compatibility with your sanitiser |
| Membranes and fine filters | Oxidative damage shortens life | Check manufacturer limits on oxidant exposure |
| Emitters and dosing internals | Degradation at high concentration | Flush thoroughly after high-dose treatment |
Dosing Control
- Inject into a well-mixed point and allow genuine contact time before the first plant or surface
- Measure residual at the far end of the loop, not only at the injector
- Account for demand. Dirty lines and high organic load consume oxidant before it does anything useful
- Calibrate dosing equipment on a schedule — the pump is only as honest as its last check
- Alarm out-of-range dosing where a failure could harm plants or people
Safety and Storage
- Never store incompatible chemicals together. Acids and oxidisers have their own segregation rules
- Segregate and label every container, with safety data sheets accessible at the point of use
- Provide bunding for stored volumes and a documented spill procedure
- Ventilate dosing rooms adequately, especially for products that generate gas
- Issue the right PPE — gloves, eye protection and respiratory protection appropriate to the product
- Train staff on handling and emergency steps, and re-train annually; injuries nearly always involve either a shortcut or an untrained person
Cost Compared Honestly
Unit price per litre is the least useful number available. Compare instead:
- Cost per treated volume at the actual concentration you need
- Contact time and labour to achieve the required effect
- Corrosion cost — replacing a run of fittings costs far more than chemical savings
- Monitoring cost and how easily residual can be measured
- Disposal constraints if local rules limit what can go to drain
FAQ
Which sanitiser is best overall?
None universally. Peracetic acid and chlorine dioxide are strong disinfectants for between-cycle work; hydrogen peroxide suits gentler routine control. Decide by application, materials and local registration.
Can I rotate sanitisers?
Yes, and it is often sensible — rotation reduces the chance of tolerant populations establishing. Do it deliberately, with records, rather than whenever supplies run short.
Will sanitiser harm my plants?
At in-crop rates properly monitored, usually not. Damage typically comes from overdosing, poor mixing, or applying a high-rate disinfectant while plants are present.
Do I need to neutralise after high-dose treatment?
Sometimes, depending on product and disposal route. Check the label and your local discharge rules; some jurisdictions require treatment or permitted dilution before release.
How do I know it worked?
Verify. Use residual measurement for routine work, and consider swab or water testing after a deep clean. Without verification you have an expense rather than a control.
Does a sanitiser replace cleaning?
No. Debris and biofilm shield organisms from contact. Clean mechanically first, then disinfect — this order matters more than the product choice.
Choose It With Your System in Mind
Material choices made now — pipe, seals, tank fittings — determine which sanitisers you can use for the next decade. Send us your loop design and water analysis and we will flag compatibility risks before installation. Start from the quote form.
Related reading: sanitisers connect to several programmes — see cleaning and sanitizing between cycles, root rot in NFT and DWC, controlling algae, food-safe materials and certification and runoff rules and compliance.