Equivalent Tenements Explained

It is not practical or cost-effective to install, maintain and read sewage meters on each property that we service, so we estimate the load and the cost to attribute to each property. Utilities around Australia estimate the sewage load that properties place on their networks in different ways. We use an Equivalent Tenement (ET) method to calculate sewerage prices.

One ET is the estimated load of sewage from an average residential house in dry weather flow conditions. It is a proportion of a water ET, on the basis that a proportion of ‘water in’ will appear as ‘water out’. ET sewage rates for different land uses are calculated as a factor of this load. For example, where the use of a property has the potential to result in sewage flows four times as much as that of one residential property, it will be assessed as four ETs and will pay four times the sewerage charge of a residential property. 

Our ET approach is based on Section 64 of the Determination of Equivalent Tenements Guideline of the NSW Water Directorate. The ETs from the Guideline have been adjusted for Tasmanian conditions, to reduce administrative complexity, increase fairness or to respond to customer concerns. Supplements are the WSAA Sewerage Code of Australia: Part 1 and the TasWater Supplement to the WSAA Gravity Sewerage Code of Australia.

Water ETs are based on actual average water use. An assumed discharge factor is applied to arrive at a sewage ET. For one sewage ET, the assumed areas of water use in a house are set out below:

  • Kitchen – 15 per cent
  • Laundry – 25 per cent
  • Toilet – 30 per cent
  • Bathroom – 30 per cent.

For the PSP4 period, we have made a number of refinements to improve the fairness and accuracy of our ET approach, including:

  • Combining some ET categories to reduce complexity
  • Updating ET unit measures to more accurately reflect load on the system
  • Refining categories and ET units for customers who also pay trade waste charges. 
Equivalent Tenement assessment process

ET assessments start at a minimum of one ET, except for unconnected properties within serviced land, which are assessed at 60 per cent of a full ET. Connected properties are charged a minimum of one ET. To calculate the number of ETs, the property type is first determined using combined data sources such as site visits, local knowledge, Google maps, direct customer contact and council data. For residential properties one ET is attributed.

For non-residential properties, the following steps are undertaken: 

  • Ascertain the ET units: such as number of beds or rooms, number of staff and students, gross building floor area (GBFA) and/or applicable amenities
  • Determine unit price, based on property type, as a proportion of one ET
  • Apply unit price to the ET number to get a total price
  • As above, 0.6 ET is attributed to properties within serviced land not connected to TasWater’s infrastructure. 

Equivalent Tenement rates

A table of the ET rates for different property types is set out here.

Equivalent Tenement re-assessment

TasWater has arrangements in place for customers to have your ET calculation reassessed if you believe it is inaccurate.

An ET reassessment may result in an increase or decrease in your ET rates. The new rates will be applied to your account from the next billing period.

Please contact us by email on [email protected] with 'ET' as the subject heading or phone 13 6992.

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