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Aviation Products // Line Maintenance & Exterior Cleaning

Aircraft Pipe and Tank Cleaner
  • Biodegradable fast acting formulation for in-place cleaning
  • Descales aircraft toilet system quickly and safely
  • Thickened for better cling on vertical surfaces
  • Safe on stainless steel, most plastics and paints
  • Conforms to AMS 1640C and BSS7432 (Toilet Flushing Liquids)


Callington Unblock-S efficiently removes scale deposits and prevents scale buildup in aircraft toilets, serving as both a preventative maintenance measure and a powerful cleaning tool during heavy maintenance checks. It can be used for soaking or recirculation cleaning by Airlines/MROs, ensuring smooth operations and reducing the risk of Aircraft on Ground (AOG) incidents


Callington's Unblock-S is suitable for both vacuum and recirculating toilets. It is powerful enough for deep soaks during engineering checks and can also be used diluted in a regular cleaning cycle.

Directions for Use

Frequency of treatment will depend upon waste line conditions, scheduling and requrements for each airline. For routine/regular Preventative Maintenance we recommend treating at intervals of at least two weeks for all aircraft types.
1L of product per toilet is recomended for narrow-bodied aircraft and 2L per toilet for wide-bodied aircraft.


For vacuum toilets: 
Crushed ice is not required to improve Unblock-S. Using instructions:

  1. Start the cleaning process at the most forward lavatory by putting the required amount (1L or 2L) of Unblock-S down each toilet.
  2. Flush the toilet as many times as needed (generally twice) to remove the products from the toilet bowl and disperse the Unblock S into the pipe system.
  3. Complete this procedure for all toilets on the aircraft.
  4. Results will be improved the longer the cleaner stays in the waste line. No additional flushing should be required until the next passenger's use of the lavatory, as Unblock-S is safe for long term exposure.
  5. Drain and service the waste tank after all the toilets have been treated.

Re-circulating Waste Holding Tank: Use Unblock-S at 1:1 (50%) dilution with clean water. Crushed ice is not required to improve Unblock-S.

  1. Make sure that lavatory holding tanks have been emptied and flushed with clean water or lavatory deodorant to remove any waste contamination.
  2. Charge the waste tank with Unblock-S diluted 1:1 with water until level with the flapper valve.
  3. Complete this procedure for all toilets on the aircraft.
  4. Allow cleaning solution to remain in the system as long as possible (generally around 7 to 8 hours) and periodically flush at hourly intervals to re-circulate the cleaner.
  5. When the cleaning operation is complete, drain and rinse holding tanks with clean water or Callington's Bioclean 360SC lavatory deodorant to remove Unblock S before adding a fresh batch of Bioclean 360SC lavatory deodorant.

Vacuum Toilet Systems:
  1. Pre-treat by pouring 1 litre of toilet deodorant such as Callington's Bioclean 360SC diluted at 1:640 into each toilet and flush to minimise the malodour from the vacuum lines.
  2. Unblock-S can be used in conjunction with the Recirculation Cleaning Tool/Equipment operated by the Airlines/MROs during heavy maintenance checks.
  3. Charge the chemical into the aircraft vacuum waste lines in accordance with the instructions in the User’s Manual of the Cleaning Tool/Equipment to achieve maximum performance.
  4. At the end of the cleaning process, discharge the used chemical and dispose of it in accordance with the local regulatory requirements for chemical disposal. For more information consult the product SDS.


• Conforms to AMS 1640C and BSS7432 (Toilet Flushing Liquids)

Physical Properties

Appearance:               Dark blue to slightly green liquid (Pink in EU)     

Density at 20°C:         1.05 ± 0.03g/mL       

pH:                              1 - 2

Ordering Info

Product CodePackaging
5120/42 5L
5120/51 20L
5120/64 200L
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