OSD – On-site Stormwater Detention

It’s commonplace nowadays If you’re in the process of building a new home or new project, your local council might require a retention tank fitting.  Often this depends on the location of your building and how effective the local storm water management system is. 

An OSD – On-site stormwater detention fitting on a tank is simply a way of retaining some water for re-use and other water for slow release back into the storm water.  This is often required when local council storm water is deemed not suitable to drain all the water from a downpour into the stormwater system adequately.  As you can imagine with many new buildings the water running from the roof at one time would be huge.  Often this can cause flooding on the streets etc.  Therefore, with a tank that has an OSD fitting part or all of the water is captured and then slowly released into the stormwater. 

Accordingly, OSD tanks have an additional fitting called and OSD fitting that release water flow over time.

Most new homes and larger renovations in particular areas now require a retention fitting to achieve their certificate of occupancy. The size of the tank that is required to be installed is usually noted on stamped plans.

OSD fittings can be installed in various ways:

  1. Installed during manufacturing
  2. Installed on poly tanks and poly welded by a qualified poly welder
  3. Installed by plumber on site as an aftermarket addition*.

*Please note that if any fitting is inserted as an after-market addition, and leaks arise at the instal site, the tank manufacturers warranty is not valid.  The fitting installer (plumber) would be required to mend.

Installation is fairly simple for the after-market OSD kit for poly tanks. The installer drills a hole to fit the 100mm fitting.  The installer drills the orifice plate to the required specifications on the plans.  Install OSD kit.

Some builders prefer the OSD kit to be poly welded by a professional poly welder.  This is completed prior to the tank being delivered to site.  This will eliminate any chance of leaks around the insertion site.

Detention Tank, Retention Tank, OSD Tank