A moulded air and water distribution block laid in rows across the floor of a denitrification or BAF filter tank. The bricks form the filter bottom that carries the support gravel and media above them, collects filtrate evenly, and spreads backwash water and air over the whole tank floor instead of at a single inlet.

A filter bottom made of bricks is built from repeated identical modules. Each brick adds its own distribution channel to the row, so the collection and backwash surfaces extend right across the tank instead of being concentrated near the inlet.
The bricks are laid as parallel rows that together form the underdrain. Backwash water and air enter the channels formed by the mouldings and are released along the full length of the floor, so the media bed is lifted evenly rather than at a few points.
Each brick is a separate module with locating edges, so a row is set out brick by brick and kept to a common level across the tank. The layout is repeated and predictable, and a single brick can be lifted for inspection or replacement during maintenance.
The brick is a one-piece moulding with no joints or fixings inside the water path. It resists the corrosion and abrasion of repeated backwash cycles and adds little weight to the tank floor compared with a concrete bottom.
| Parameter | Value |
|---|---|
| Product type | Moulded air and water distribution filter brick (underdrain block) for filter tank bottoms |
| Typical use | Denitrification filters, biological aerated filters (BAF), deep-bed down-flow filters |
| Block profile | S-type and T-type profiles — final profile confirmed on request |
| Material | On request — moulded thermoplastic (HDPE) compound, confirmed by grade |
| Nominal block dimensions (L × W × H) | On request |
| Block mass | On request |
| Joint between bricks | On request — locating edges and capping plate arrangement confirmed with the profile |
| Water distribution channel | On request — confirmed against the tank layout and backwash duty |
| Air distribution / air-scour channel | On request |
| Slot / orifice arrangement and open area | On request |
| Block compressive strength | On request |
| Colour | On request — grey, blue and black mouldings are shown in the gallery below |
| Support layer above the bricks | Graded support gravel and filter media, matched to the media depth and backwash rate — on request |
| Bricks per square metre of tank floor | On request — calculated from the tank plan and the block footprint |
| Export packing | On request — banded and strapped units on pallets |
| MOQ / price | On request — confirm the tank plan, quantity & destination |
Items marked on request are confirmed for the specific tank and duty. They are not fixed catalogue values, and no performance figures are published for them.












Send the tank plan, the block profile you need, media depth and backwash air and water rates — we will confirm the brick layout, the number of blocks and the export packing.
Request a QuoteNo obligation · response within 24h (working days)