Choose a clay arrestor when the sink mainly receives clay residue, a plaster arrestor when it receives plaster waste, and a combined clay and plaster arrestor where both can reach the same drainage point.
The room name will not tell you. An art room might use clay, plaster or both, and medical, casting and workshop areas all carry different waste streams. Work out what gets washed off the tools and containers before you pick a model.
What does an arrestor do?
A clay or plaster arrestor sits between a sink or trough and the drainage system. It captures suspended solids before they travel further into the pipework, where they settle, harden and eventually block it.
An arrestor does not make it acceptable to tip unlimited waste down a sink. Excess clay and plaster should still be scraped off, reclaimed or binned before washing. The arrestor catches what the wash water carries with it.
When should you choose a clay arrestor?
A clay arrestor suits sinks where clay is the main solid going in. Think pottery rooms, ceramics studios, school art spaces and workshops where clay tools and containers get washed.
Clay particles settle inside drainage pipework. Removable filter baskets give that material somewhere accessible to collect before it reaches the plumbing downstream.
The Marko Stainless & Aluminium CP1 Clay Arrestor has a 67 litre capacity, 50 mm BSP inlet and outlet, removable filter baskets and a removable lockable lid. It is fabricated from 1.2 mm 304 Grade No.4 stainless steel, with custom 316 Grade available.
Its larger capacity does not make it the right unit for plaster. The waste type and the internal arrangement have to match the application.
When should you choose a plaster arrestor?
A plaster arrestor, sometimes called a plaster trap, is meant for sinks where plaster residue comes off tools, bowls, moulding equipment or similar items.
Plaster left sitting in a drainage system will settle and set. Catching it in an accessible arrestor means it can be lifted out before it becomes a plumber’s problem further along the line.
The CP3 Plaster Arrestor has a 53 litre capacity, 50 mm BSP inlet and outlet, removable filter baskets and a removable lockable lid. It suits art, casting, educational and medical environments.
When is a combined arrestor better?
Choose a combined unit where clay and plaster can both be washed through the same sink or trough.
The CP2 Clay and Plaster Arrestor captures both waste types and has a 58 litre capacity, 50 mm BSP inlet and outlet, removable filter baskets and a removable lockable lid. It works well in multipurpose art rooms and shared studios where separating the sinks is not realistic.
A combined arrestor is not required just because both materials get used somewhere in the building. The question is whether both waste streams can reach that particular sink.
Clay, plaster and combined models compared
| Model | Intended waste | Capacity | Connections |
| CP1 Clay Arrestor | Clay | 67 litres | 50 mm BSP inlet and outlet |
| CP3 Plaster Arrestor | Plaster | 53 litres | 50 mm BSP inlet and outlet |
| CP2 Clay and Plaster Arrestor | Clay and plaster | 58 litres | 50 mm BSP inlet and outlet |
All three are manufactured as standard from 1.2 mm 304 Grade No.4 stainless steel, with custom 316 Grade construction available. The full clay and plaster arrestor range also includes matching dollies.
Maintenance access is not optional
An arrestor only protects drainage while it is being inspected and cleaned. Install it somewhere staff can lift the lid and pull the baskets without dismantling joinery or shifting equipment.
Where the unit sits under a bench or needs moving for cleaning, a clay and plaster arrestor dolly makes the job manageable for one person.
Cleaning frequency depends on how the room gets used and how much material reaches the unit. Inspect a new installation often at first, then set a schedule around the rate it builds up.
Do not wait for slow drainage or an overflow. Collected material should be handled and disposed of under the facility’s waste procedures and the applicable local requirements. In the Hunter, Hunter Water sets the trade waste conditions for what can be discharged to sewer, and other regions have their own water authority requirements.
What should be confirmed before ordering?
Provide:
- materials used in the room
- number of connected sinks
- expected usage and waste volume
- inlet and outlet locations
- space available around the unit
- cleaning and maintenance access
- whether a mobile dolly is required
- plumbing drawings and installation scope
Coordinate the arrestor with the art trough or sink, the joinery and the pipework. A plumber should confirm the final connection and drainage arrangement.
Frequently asked questions
Can one arrestor handle several sinks?
Potentially, but flow, waste load and plumbing layout all need assessing first. Do not assume one unit will cope because the sinks happen to be near each other.
Is a plaster arrestor the same as a grease arrestor?
No. A plaster arrestor captures plaster solids. It is not a substitute for a system designed around a different waste stream.
How often should the baskets be cleaned?
There is no single interval. Inspect frequently when the unit is first installed, then set a schedule based on real use and accumulation.
Do arrestors capture paint or chemicals?
They are designed for clay and plaster solids. Paints, solvents and chemicals need managing according to their safety information and the site procedures.
Selecting the right arrestor
The choice follows the material entering the sink: CP1 for clay, CP3 for plaster, CP2 where both waste streams share a drainage point.
Marko Stainless & Aluminium manufactures stainless steel arrestors for schools, art studios, medical facilities and commercial projects from our Cardiff workshop.
Send us your sink layout and waste requirements to work out the right arrestor for the job.
