Plastic pellets, flakes and regrind travel further than most sites expect. A handful spilled at a coupling gets swept, walked, blown or washed towards the nearest drain, and once it is in the drainage system it is effectively gone.
Five forms: yard gully bucket, B1, D1, C3 and A4 · pre-fitted textile filter insert nominal 70 µm · galvanised steel buckets for yard and road gullies · retrofit inserts for compatible existing buckets
A plastic pellet retention system puts a barrier at that last controllable point. A plastic pellet drain filter works at that point: a galvanised bucket sits in the gully pot, a textile insert with a nominal 70 µm rating is fitted over the bucket opening, and the water passes through the fabric while the pellets stay behind. The bucket is permanent. The insert is the part that gets changed.
This is the point that decides most orders, and it is counter-intuitive enough to say plainly.
Two of the five forms hold almost exactly the same volume. A4 and C3 are both around 70 litres. They are not interchangeable, because one is narrow and deep and the other wide and slightly shallower. What decides between them is the pot, not the capacity.
| Form | Diameter | Height | Volume | Choose when |
|---|---|---|---|---|
| Yard gully | Ø 260 mm | 250 mm | approx. 13 l | small point drainage close to the process |
| B1 | Ø 305 mm | 250 mm | approx. 18 l | clear depth is the constraint |
| D1 | Ø 395 mm | 325 mm | approx. 40 l | wide pot, limited depth, manual extraction |
| C3 | Ø 395 mm | 575 mm | approx. 70 l | wide pot with full depth |
| A4 | Ø 385 mm | 600 mm | approx. 70 l | narrow deep road gully, high sediment load |
Volumes are derived from external dimensions and are an orientation. Wall thickness, base construction and fill level change the usable quantity.
Two measurements settle it: the clear internal diameter of the gully pot at its narrowest point, and the clear depth from the underside of the grating seating to where the bucket would rest. With those two figures we can tell you which form fits, and whether any of them does.
Standard pellets are in the millimetre range and are held comfortably by a 70 µm textile. Flakes and regrind vary: the coarse fraction is retained, the finest dust fraction is not. That is the accurate description and it is the one we stand behind.
We do not claim complete retention, and any supplier who does should be asked for the test behind it. What a retention system delivers in practice depends as much on the servicing regime as on the fabric. A well-chosen system that is checked weekly retains far more over a year than a finer one that is fitted and forgotten.
Worth being direct about, because the market around this topic sells certainty that nobody can supply.
Losses happen at transfer points, during cleaning, at bulk handling, in maintenance and during incidents. Retention at the drain catches what escapes the other measures. It is the last line, not the first, and it works best when the measures upstream are already in place: closed transfer, dry sweeping before washing down, defined procedures for spills, and drains that are known and mapped.
A retention system therefore supports pellet loss prevention. It does not deliver it on its own.
Two things are usually mentioned in the same breath and they are not the same kind of thing.
EU Regulation 2025/2365 sets obligations for operators who handle plastic pellets. Those obligations sit with the operator and cover handling, procedures, documentation and, depending on scale, external verification. They are not discharged by installing a product.
Operation Clean Sweep is a voluntary industry programme. Participation is a commitment made by a company, not a certification awarded to equipment. There is no such thing as an OCS-certified filter.
WINKLER supplies retention hardware and does not certify compliance with either. A retention system can be part of what a site puts in place and can be documented as such. Whether a site meets its obligations depends on the full set of measures and the evidence behind them. The background, including where the two frameworks differ, is set out in the guide.
Nurdle is the informal term for a plastic pellet, used widely in the UK and in the marine litter context. A nurdle filter or nurdle trap in a drainage context means what this page describes: a retention system in the gully that keeps pellets out of the surface water system.
The terminology matters for one practical reason. Enquiries that arrive using the marine litter vocabulary often come from a different starting point, usually an environmental commitment rather than a process problem. The technical answer is the same, but the measurements we need are identical either way: pot diameter and clear depth.
Where suitable buckets are already in the pots, replacement inserts can be ordered on their own. The inserts are matched to the five WINKLER bucket forms. There is no universal fit, and a poorly seated insert lets material pass while looking like a working system. Send the opening diameter, the height and a photograph of the rim and we will check it.
Two measurements decide it: clear internal diameter at the narrowest point and clear depth to where the bucket rests. Send both and we will name the form.
No, and no product can be. Operation Clean Sweep is a voluntary commitment made by companies, not a certification scheme for equipment.
A loaded insert restricts flow, and water will take the path of least resistance. We make no claim in either direction about what happens under surcharge, because it depends on the pot, the inlet and the condition of the insert. This is the reason the check routine matters more than the specification.
No. The obligations sit with the operator and cover procedures, documentation and verification. A retention system can be part of the measures and can be documented as such. It does not discharge the obligation.
On condition. Water standing in the bucket after an event, visible damage to the textile, or a fill level that prevents even loading are the three indicators. Near a transfer point, weekly checks are a sensible starting routine.
They will collect whatever the drain carries, including grit and sediment. On a trafficked surface that mixed load fills the bucket faster than pellets alone and loads the insert sooner. Factor it into the form choice and the service interval.
Selection guidance and technical background for the products in this category.
Plastic pellet loss prevention ➔ where losses happen, which measures work and how EU 2025/2365 and OCS fit in. Read the guide!
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