Another great RocketTheme Joomla Template brought to you by the RocketTheme Joomla Template Club.
Home Maintenance Advice Charge Systems
Charge Systems Print E-mail

Charged systems increase the roof area that can be harvested and once installed are low maintenance if well designed. The key issues are screening the stormwater system and providing a drainage point at the lowest point of the stormwater system to periodically drain stagnant water and any material that has entered the system.

What is a Charged System?

Quite simply a charged system or wet system is where the stormwater downpipes from the roof are drained below the inlet to the rainwater tank. As additional water flows from the roof into the downpipe the water is ‘pushed’ back up to the inlet point. For example this allows the roof on one side of a house to be drained to an underground pipe, directed around the house to the water tank and then led back up to the inlet point. As a result there is always water in the downpipe system (it is already ‘charged’) even when it isn’t raining.

What can go wrong?

Charged system don’t have a gravity flush, any non-dissolved material carried by water into the system is likely to stay in the downpipes leading to the rainwater tank. Decomposition of this material, usually leaves, is likely to lead to brown water, smells and less than fresh tasting water.  Similarly insects including mosquitos can live and breed in this water.

The flow rate of the stormwater system is an issue if more water is entering the stormwater system than entering the tank inlet. Stormwater will back up the downpipe and overflow the gutters if the system is not well designed.

What additional barriers should be put in place for charge systems? (material from Rainwater Tank Design and Installation Handbook HB230)

  • Downpipes discharging to the rainwater tank for wet systems (water charged) should have a minimum 100 mm vertical distance between the rainwater head and the tank inlet. If the roof runoff is greater than the flow rate of the stormwater pipes this allows overflow to occur at this point.
  • The rainwater head should be leaf screened and vermin and insect proofed (including mosquito screening). This prevents leaves, vermin and insects remaining in the water in the stormwater system.
  • The stormwater system should be designed with the provision to drain stagnant water during dry weather periods (e.g. capped relief access point at lowest level of stormwater drainage system).
  • Unless in use, all access points, excluding the inlet and any overflows, should be kept shut with close fitting lids that will prevent mosquito access. Inlets and overflows should be covered with closely fitting removable insect-proof screens.

Queensland (1996) and Northern Territory (1998) regulations specify the characteristics of insect proof screens as follows:

(i) Queensland—Brass, copper, aluminium or stainless steel gauze not coarser than 1 mm aperture in a charged or wet system (Figure 15.3).

(ii) Northern Territory—Brass or bronze wire not coarser then 7 meshes to the centimetre (each way) and of 33 gauge wire (approximately 1.25 mm holes). Guidance in Western Australia (2003) indicates that insect-proof mesh should be no coarser than 12 ´ 12 meshes/25 mm2 (approximately 1.9 mm holes with 33 gauge wire).  

(iii) All other States specify that all inlets and outlets have to have insect-proof mesh fitted.


This material has been prepared as a result of discussions with the NSW Department of Planning although RHAA is solely responsible for the material. The RHAA provides these as general principles with no implied liability for the advice. In all circumstances you should rely on your own sources for advice that will meet your specific needs. 



Last Updated on Thursday, 29 October 2015 14:10
   © Copyright Australian Rainwater Industry Development Group | Legal Notices | Sitemap