Balcony Drainage

If you are going to have a balcony don’t forget to consider  the drainage.

You need to make sure that you have a large enough drain, for example this.

And the whole balcony slopes down to the drain.

If the drainage isn’t done properly you are going to have staining on the front of your house.

Here are a couple of photos of balconys with drainage problems.

This is a really bad example of staining where it looks like there was no drain, and the water drains off the edge.


Although this isn’t as bad you can see that some water has been staining the building as water runs out of the grout between the tiles.

Different Roof Drainage

Most of us are used to the traditional Australian roof drainage connecting to down pipes . . . . but this isn’t how everyone sees it.

The Hawaii Solution

Travelling around Hawaii I was quite surprised to see how many houses completely dispensed with any form of roof drainage like this photo.

No Gutters and no downpipes.

OK as long as you aren’t building on Reactive Clay

Not a problem in Hawaii where it is mainly volcanic sands or rock.

The Frank LLoyd Wright Solution

I recently talked about visiting some Frank Lloyd Wright ‘Prairie Houses’ in America.

With the ‘Prairie House; style there was an emphasis on horizontal lines.

To avoid the strong vertical lines of the downpipes Frank just got rid of them.

To collect the rain below each discharge point he positioned a pit like this one.

The only problem is that in the slightest breeze there is going to be a lot of spray.

The Japanese Solution

This system of a chain of cups is a fairly common Japanese alternative to a down pipe.

For small flows the water drains through each cup to the one below it.

With heavier rain the flow runs on the outside of the cups where it is held to the cup by surface tension.

If you can’t get hold of the Japanese cups a simple chain can work just as well.

Water Bills

I hear a lot of complaints about Water Bills . . . . . but Town Water is one of the ‘Great Bargains’ of our age!

Don’t Believe Me?

Well lets look at the facts.

Typical Water Charges

Well I live in Melbourne’s City West Water area so my  water charges are:

Water Service Charge

$54.65/quarter. This is to cover things like the maintenance of the thousands of km’s of pipes that  are ready to deliver the water to you.

Water Usage Charge

To encourage people to be responsible in the water usage the cost/kilolitre rises at 440 litres per day and again at 880 litres per day. (The average Melbournian uses 160 litres per day, but my wife and I are careful and only use around 100 litres each per day)

  • $2.3060 per kilolitre for the first 440 litres of water used per day.
  • $2.7241 per kilolitre for water usage above 440 and up to 880 litres per day.
  • $4.0749 per kilolitre for water usage above 880 litres per day.

Cost For A Family

Well the daily cost for an average family of 4 using 640 litres per day is:

1st  440 litres  $1.01

2nd 200 litres $0.54

Service Charge $0.60

Total $2.15 /day     (Equivalent to $3.36/kilolitre)

Remember this is for a product that has been; Collected, Stored(for up to 4 years), Treated, and Delivered to your tap exactly when you want it.

Some Comparisons

You may not be familiar with what a kilolitre really means but here are  3 equivalents.

  1. It weighs one tonne.
  2. It is equivalent to a cube 1m x 1m x 1m.
  3. Just over 4 large wheelie bins.
  4. 2,000 x 500ml bottles

Comparison With Any Other Product

If you can find any other product that you can have delivered to your door for $3.36/ tonne let me know . . . even dirt costs around $60/tonne.

Comparison with Bottled Water

Well the cheapest I could find bottled water was in my local Costco, where it worked out at $500/kilolitre!

Comparison with Beer

One days water supply = the cost of 1 stubby.


Still think Town Water is expensive? . . . . Then leave a comment!




Soil Heave – Protecting the Slab During Construction

There has been a lot of talk in the Melbourne papers recently about ‘Slab Heave’ when Building on Clay so I thought I would explain how to minimise the risk during construction.

A key issue when building on clay is to avoid any extra moisture getting into the clay under the slab. causing the clay to swell, by keeping the area around the slab well drained.

This is particularly important where part of the slab is below the natural ground level such as when ‘Cut and Fill’ is required to get a level site.

Detail For Protection Against  Soil Heave

The diagram below shows what you should be looking for, during construction, to protect the ground under your slab from gaining moisture.

The key issues are:

  • The excavated surface falls away from the edge of the slab for at least 1m with a minimum drop of 75mm.
  • Where the water will not continue to flow away from the slab an Aggi Drain in a granular back filled trench should be provided. This drain should be a minimum of 100mm below the surface level of the clay and fall to a suitable discharge point.
  • Any trench in the area between the slab and the aggi drain should be topped with well compacted clay to ensure there is no easy passage for water to penetrate under the slab.
  • Roof drainage should be connected to a suitable point of discharge as soon as possible after the roofing material is fixed. (See Temporary Downspout)

Although the requirement for an aggi drain is not as critical where the ground slopes away from the slab, it is nevertheless good practice to have one.


Also see Agricultural Drains


Onsite Stormwater Dention – Why

If you want to redevelop or subdivide an existing urban house block, you might find that a planning condition is that you will need to provide On-site Stormwater Detention (OSD).

You may also find it is a condition on individual blocks on smaller subdivisions.

Why Is Onsite Stormwater Detention Needed?

Before development of towns and cities a large proportion of the rain that fell in an area soaked into the ground or flowed slowly across the land to a creek or river. When areas started to be developed two things happened:

  • More and more of the land was built on, or paved, which meant rain was unable to soak into this ground.
  • Stormwater drains were built to carry the rainwater quickly away from the houses to be discharged into streams and creeks.

Initially while Australia had a small population this didn’t cause too many problems.

Since the mid 1950’s and the rapid growth in population more and more land has been built on.

The result has been more and more water has been discharged surface water drainage systems causing overloading of the piped systems and flooding of the rivers.

In order to try and reduce flooding Planning Authorities are attempting to reduce rainwater flows from developments to a flows similar to an undeveloped site.

OSD On Large Subdivisions

If you buy a block on a large subdivision it is unlikely that you will be asked to provide OSD on your Block.  This is because large developers  as a condition of the overall development have to provide Stormwater Detention Storage for the whole development.

The way they usually do this is by making much of the open space they also have to provide as Ponds, Lakes or Wetlands, which can fill up during periods of rain and then slowly empty. (Now you know why so many developments have a reference to Water in their name)

Other posts will explain more about how the Storage Volumes are Calculated and will look at various storage options.

Guide to Buying a Block has lots of info like this on what to look for before you buy land.


Stormwater – Kerb Discharge

If you are going to build on an existing house block you will probably have a planning permit condition that storm water must discharge to an approved point.

If there is no surface water system one option can be to discharge to the street.

This is normally by constructing a proper kerb outlet like the photo below:

But not like this dodgy installation on the right!

Or even discharging over people walking along the path like the one illustrated in this post: Overflow Fail

A kerb connection can be at a reasonable cost as long as the house is above the road.

If the house is below the road you will need either:


  • A pump and storage for the storm water, which can add significantly to the build cost.


For more information on issues like this see Guide to Buying a Block


Plumbing Acronyms

There are a lot of acronyms used on plumbing drawings so here are a few definitions:

AGAgricultural (Drains)
B – Basin
Bth – Bath
BT – Boundary Trap
DP – Down Pipe
FW – Floor Waste
HWS – Hot Water Service
IC – Inspection Chamber
IS – Inspection Shaft (also IO -Inspection Opening)
ORGOverflow Relief Gully
PRV – Pressure Reducing Valve
RRJ – Rubber Ring Joints
RWH – Rain Water Head
SHR – Shower
ST – Stop Tap
SW – Storm Water Pipe (or SWD – Storm Water Drain)
SWJ – Solvent Welded Joints
TR – Laundry Trough
VC – Vitrified Clay
VP – Vent Pipe (sometimes UVP – Upstream Vent Pipe)
WC – Water Closet (Toilet)
S –  Kitchen Sink
SV – Stop Valve

If you have seen an acronym you don’t understand, then let me know, and I will try to give you an answer.

See Jargon for more posts


Protecting Underground Pipes

One of the problems that happen all too often during a new house build is that Sewers and Drains get filled with concrete.

Its normally happens on:

  • A knock down and rebuild project where the sewer connection wasn’t sealed during demolition.
  • A Battle Axe block subdivision where the new home is built close to the pipeline.

During the pouring of the foundations the concrete gets into the pipeline through the unsealed connection, or a cracked pipe, and then flows along the pipe.

Our company then gets brought in to remove the concrete using a hyraulic impact cutter like this.

Don’t think its cheap though . . . . . . It normally takes a team of three plus a high pressure jetting truck so the costs is upwards of $200 an hour, and its not unusual for one job to take 2-3 days.

To understand more issues when purchasing land see: Buying a Block


Charged Drainage System

Thanks to SaveH2O, of Supadiverta

This diagram indicates a charged drainage system. These are sometimes called either a “wet” or a “pressure” system.

With this type of system a section of the pipe always remains full unlike a Conventional System.

As the pipes are under pressure it is essential all the joints in above ground and underground pipework are fully watertight


  • A neater appearance than having pipes above ground.
  • Allows you to discharge water at a height above the ground level at the down pipe.


  • It is more likely to block as the flow through the pipes can be fairly slow and the low points can collect silt. Silt will get deposited at flow rates below 0.6m/sec which will be the situation for most rainfall events.
  • It is also more difficult to unblock.
  • Can cost more with excavation and additional inspection fittings .
  • Potential for mosquito  breeding  in water unless appropriate screes are installed.


Also see Underground Pipes


Conventional Drainage

The vast majority of new houses will have a conventional (sometimes called a Gravity, or Open system) storm water drainage system discharging to either:

    • Public Surface Water Drain – Typically in Eastern States
    • Soakwells on Sandy Sites – Mainly in WA


With a conventional system like this the pipes are either vertical or at a slope towards the discharge point.

A feature of this system is that when there is no flow all the pipes are empty.


  • Simple and inexpensive to design and construct.
  • If well designed, and constructed,  the speed of flow in the pipes will prevents silting and subsequent blockage.


  • This type of system can look very untidy when taking water to a Rainwater Tank that is some way from many of the downspouts (It results in lengths of pipes suspended in mid air)
  • Difficult to transfer water to a discharge point that is above the ground level of the building, although below the gutter level. A problem often encountered on demolition and rebuild projects and battleaxe blocks.

If you are planning a rainwater tank or are having problems with getting storm water to a suitable discharge point you could consider a Closed System


Also see Underground Pipes