Ensure fully compliant, high-capacity site sanitation with our 3+1 Welfare Unit Sit-On Waste Tank (6,500 Ltr / 1,400 Gal). Specifically engineered to sit directly underneath standard 3+1 site toilet blocks, welfare units, and portable office containers, this low-profile effluent holding tank provides high-volume waste storage for un-mainsed construction sites and outdoor events. Built from heavy-gauge structural steel with reinforced internal bracing, low-level emptying ports, and multi-point suction connections for rapid vacuum tanker servicing across the UK.
£2,690.00
When operating construction sites, infrastructure projects, or temporary event spaces without direct access to mains drainage, managing waste safely and hygienically is critical. The 3+1 Welfare Unit Sit-On Waste Tank (6,500 Ltr) offers a reliable, high-capacity solution engineered to collect blackwater and graywater directly beneath 3+1 toilet blocks and welfare cabins.
By placing the waste tank directly under the container footprint, site managers maximize available ground space while maintaining full compliance with UK Health & Safety Executive (HSE) workplace welfare guidelines.
Space-Saving Footprint: Designed to sit flush under standard 20ft x 8ft welfare containers, eliminating the need for dedicated lateral ground space or deep ground excavation.
Reinforced Steel Framing: Built with internal structural bracing and heavy-duty top plates designed to safely support the full static load of a fully occupied 3+1 welfare block.
Multiple 110mm Waste Inlets: Pre-drilled and fitted with standard 110mm / 4-inch PVC inlet sockets to line up directly with internal toilet downpipes, urinals, and handwashing sink connections.
Bauer Connection Extraction Ports: Fitted with quick-release 4-inch and 6-inch Bauer connections, allowing waste management contractors to pump out the tank efficiently without disturbing site operations.
Protective Anti-Corrosion Coating: Finished internally and externally with high-build protective coatings to withstand aggressive sewage environments and extreme weather conditions.
Inspection Manholes: Features large sealed inspection hatches for straightforward internal cleaning, maintenance, and visual level checking.
| Specification Feature | Metric Value | Imperial Equivalent | Operational Details |
| Capacity | 6,500 Litres | ~1,430 Imperial Gallons | Engineered for high-frequency 3+1 welfare setups |
| Length | ~6,100 mm | 20 ft 0 in | Matches standard 20ft container footprint |
| Width | ~2,438 mm | 8 ft 0 in | Standard ISO container width alignment |
| Height / Depth | ~450 mm – 500 mm | ~18 in – 20 in | Ultra low-profile design for easy block mounting |
| Tare Weight (Empty) | ~850 kg – 950 kg | ~1,870 lbs – 2,090 lbs | Heavy-duty structural steel construction |
| Construction Material | Mild Steel / Corten Grade | — | Fully seam-welded with internal anti-surge baffles |
| Waste Inlets | Multiple 110mm / 4″ PVC ports | — | Strategically positioned for 3+1 toilet unit downpipes |
| Emptying Ports | 4″ & 6″ Bauer / Vacuum fittings | — | Fast-connect tanker extraction ports |
| Coating / Finish | Heavy-duty Bitumastic / Epoxy | — | High-durability anti-corrosion internal & external coating |
HIAB Delivery & Offloading: Delivered nationwide across the UK via HIAB crane lorry. The tank is positioned on flat, hardstanding ground prior to lowering the welfare block on top.
Ground Preparation: Requires a level concrete pad, compacted hardstanding, or heavy timber pads to ensure even weight distribution when fully loaded.
Servicing Access: Ensure clear, unobstructed access for 2-axle or 3-axle vacuum tankers within 15 metres of the extraction ports for routine servicing.
Emptying frequency depends on site usage. A 6,500 litre (1,400 gallon) tank serving a standard 3+1 welfare unit with 15–20 daily site workers typically requires vacuum tanker servicing every 2 to 4 weeks.
Yes. Our 3+1 sit-on waste tanks are engineered with reinforced internal steel bracing specifically designed to support the full static weight of loaded welfare containers and portable toilet blocks.
The tank comes equipped with industry-standard 4-inch and 6-inch Bauer quick-release suction couplings, allowing standard UK waste management tankers to connect and pump out effluent quickly.
