BWTSL-MG
$1,395.00 NZD
All prices include GST
The Big Water Tanks BWT Slimline Water Tank is the perfect solution for tight urban spaces: a 1,200 litre tank only 440mm deep, for rainwater storage and storm water detention or retention where a round tank will not fit. Designed and made in New Zealand. Need brackets, posts or a connection kit? Jump to accessories.
Modern living with only a courtyard or small backyard means a round tank may not be the most efficient use of the space, while council may require some storm water retention, detention or a combination of both. The BWT Slimline Water Tank is compact, with a depth of only 440mm, a width of 1,760mm and a height of 1,900mm, so it can be installed along a fence line or wall to store water in the most space efficient way. It is a very heavy duty tank with an attractive yet strong structure to stand the test of time. Below you will find the specifications, installation and seismic restraint information, the 10 year warranty and quick-add accessories.
| Volume | 1,200 litres (with internal overflow elbow) |
| Width | 1,760mm ± 20mm (1.76m) |
| Depth | 440mm ± 10mm (0.44m) |
| Height | 1,900mm ± 25mm (1.90m) |
| Empty weight | 75kg |
| Full weight | Over 1,300kg |
| Outlets | 2 × 32mm BSP female, factory fitted |
| Access | 2 × 355mm screw-on lids, one at each end |
| Material | MDPE (medium density polyethylene) |
| Standards | AS/NZS 4766:2020 polyethylene storage tanks for water AS/NZS 2070 food contact requirements AS/NZS 4020:2018 potable (drinking) water |
| UV rating | UV20 |
| Colours | Mist Green, Light Grey, Heritage Green, Beige, Slate Grey, Black |
| PS1 | Available on request |
Please read the installation guide before installing your tank: following it is required to maintain your warranty.
Auckland Council has an online tool to check if building or resource consent is required for your water tank: Auckland Council water tank information.
From the BWT Slimline Installation Guide. These instructions are required to maintain your warranty, and incorrect installation may result in tank failure or instability due to weather or seismic activity if the tank is not securely braced.
Seismic restraints must be installed if the tank is above ground. Holes in the stainless steel bracket plates are slotted for 12mm of adjustment to line up with the moulded-in inserts in the tank, and the brackets are bent onsite to fit the tank profile.
| Option | What You Need | Key Measurements | Concrete Slab |
|---|---|---|---|
| Seismic posts | Seismic posts (BWTSL-POST) and post bracket kit (BWTSL-POSTBR) | Posts cast into 900mm deep × 400mm diameter holes, buried 600mm into the concrete, on 1,860mm centres; 1,360mm from finished floor level to the predrilled holes. 1 tank needs 2 posts; 2 tanks side by side can share 3. | Min. 100mm thick, 20MPa with mesh; 2,300mm wide for one tank plus 1,860mm per additional tank |
| Wall brackets | Wall bracket kit (BWTSL-WALLBR) fixed with M12 anchors, min. 100mm deep | Solid filled concrete block wall, min. 140mm thick; brackets recommended at 1,360mm from finished floor level | Min. 100mm thick tied to the wall, 20MPa with mesh (or retained compacted GAP7); 2,140mm wide for one tank plus 1,860mm per additional tank |
| Other structures | Between two rigid structures, brackets into rigid structural timber (not weatherboards), a concreted timber fence with a supporting rail, or 2 stainless steel seismic straps per tank | Straps through the top two outside through holes, approx. 1,500mm from ground level | Suitable base as per the installation guide |
The onus is on the installer to confirm the structure the tank is fixed to is rigid and strong enough to support the tank in a seismic event and in everyday use. An engineer may be needed to design a specific solution for your site.
Big Water Tanks Ltd (BWT) warrants to the original purchaser that the tank will be free from material defects arising from the manufacturing process for a period of 10 years from the date of purchase, and BWT may, at its sole discretion, replace or repair a defective tank during that period, subject to the following conditions.
The warranty is void if the tank:
Excluded from the warranty: inlet holes, overflow holes or holes created on-site; change of colour over time; removable lids; reasonable weathering; consequential loss or damage including but not limited to buildings, production or the like.
Any defect must be reported to Big Water Tanks Limited within 5 days of occurrence, with photographs of the defect.
Download the Installation Guide & Warranty (PDF)Seismic restraints and connection kits made for the BWT Slimline Water Tank. Tap Add to cart to add one to your cart, or see them all on the 1200L Slimline accessories page. Kit contents are from the BWT Slimline Installation Guide.
Code BWTSL-WALLBR
2 × SS wall brackets, 4 × M10x20 SS bolts, 4 × M10 SS washers, 2 × M12x65 SS square washers. For a solid wall.
$120.00 NZD
Code BWTSL-POST
One 75×75×2.5 galvanised mild steel post, 2m long, cast into concrete. Sold individually: 1 tank needs 2 posts; 2 tanks side by side can share 3.
$160.00 NZD
Code BWTSL-POSTBR
2 × SS brackets, 6 × M10x20 SS bolts, 6 × M10 SS washers, 2 × M10 SS nuts, 2 × black plastic post caps.
$120.00 NZD
Code BWTSL-ITCC
210mm 32mm blue flexible hose, 2 × Hansen 32mm hose tails and 2 × SS hose clamps. Joins two tanks.
$100.00 NZD
The tank is 1,760mm wide, 440mm deep and 1,900mm high. For a concrete slab, allow 2,300mm width for one tank on seismic posts (2,140mm with wall brackets), plus 1,860mm for each additional tank.
Yes, if the tank is installed above ground. Options are galvanised seismic posts with stainless steel post brackets (1 tank needs 2 posts; 2 tanks side by side can share 3), stainless steel wall brackets fixed to a solid concrete block wall, or other rigid structures or strapping as described in the installation guide. Seismic restraints should not be required if the tank is partially buried 500mm, so the lower through holes are just buried.
Yes, up to 500mm from the base, on a compacted level layer of GAP7 or SAP7 at least 100mm thick, filled to at least the depth of the bury and backfilled with SAP7 or GAP7. A filtered drain coil is needed if the area could become waterlogged. See the installation guide for the full requirements.
Use the Inter-tank Connection Kit (BWTSL-ITCC): a 210mm 32mm blue flexible hose, two Hansen 32mm hose tails and two stainless steel hose clamps. Install the overflow in the same tank as the water inlet; if that is not possible, each tank needs a 100mm inter-connection with rubber tank seals at the top.
Each tank has 2 × 32mm BSP female fittings. The tank must be connected with a flexible hose (not plastic pipe like alkathene or MDPE), with thread tape on all threads. Tank plugs are not supplied with the tank.
Yes. Slow-release orifices for stormwater management can be installed at any height using a 100mm rubber seal, ideally on the same line as the overflow. Your stormwater engineer supplies the height specifications.
There are two 355mm screw-on lids, one at each end of the tank, for access.
Yes, a structural engineer's Producer Statement (PS1) is available on request.
A 10 year warranty against material defects arising from the manufacturing process, subject to correct installation and the conditions in the warranty section above. Any defect must be reported within 5 days with photographs.