DoItYourself Soakwells For
Perth Western Australia
Simple Residential Installation

Having built and sold 4 new homes in the northern suburbs region of Perth, Western Australia, I've had the "pleasant" experience of installing soakwell systems in all but one of the new homes. Because the top "soil" of the regions is, in general, a base of relatively soft sand the task hasn't been nearly as laborious as other areas of the planet I have lived. Take for instance the San Francisco Bay Area, the mid peninsula to be exact where the clay laden surface during the summer months requires the use of jackhammers and/or dynamite to get a hole dug. Here in Western Australia the sandy soil allows the approximately 1 metre x 1 metre deep soakwell hole to be dug relatively quickly. (I do highly recommend that this work be undertaken before or after November/December to alleviate the relentless attack of fly season.) The following soakwell installation procedure is by no means comprehensive but it has worked just fine for our purposes and draws a balance between cost and time and labour involved. By doing the labour ourselves we figure we've saved at least 50% on the task not to mention knowing the job has been done right. While there are no regulations written in stone regarding soakwell installation in our shire we do recommend you consult your local shires' requirements for residential stormwater runoff. Happy digging!
Soakwell material list:
  • Soakwell unit in 2 halves - $22
  • 2metre's of 90mm PVC storm water pipe - $10
  • 2 x 45 degree elbow PVC pipe joints
  • Drain pipe top
  • 20kg Blue Metal gravel
  • 600mm x 600mm concrete slab cover (showing just below)
The materials shown cost approximately $60 AUD including the 600mm x 600mm concrete slab lid when purchased at *Bunnings Warehouse*, a home improvement retail warehouse.

Alternative soakwell products are available such as this "Reln" brand at slightly higher cost.

600mm x 600mm concrete lid
600mm x 600mm concrete lid

This image shows the 2 soakwell halves "snapped" together where they join in the centre. The entry hole for the 90mm PVC stormwater pipe can be seen near the top front center of the unit.
 
Soakwell Installation Scenario 1

Here is our rainwater downspout that requires the soakwell installation.

While there are specific regulations and codes regarding stormwater runoff on residential property there are no "rigid" regulations governing the installation of soakwells other than appealing to common sense which entails, as a general rule of thumb, that the soakwell pit be dug at least 1 metre from the foundation to avoid any undermining due to water drainage. This also applies to the proximity of fence post footings. *

Area for new soakwell installation
We have begun to dig our soakwell hole approximately 1 metre from the house foundation. Partially dug soakwell hole
The hole is reaching the correct depth and should be dug wider than the soakwell itself so that we have room to work and make positioning/leveling adjustments.
Our soakwell hole has reached approximately the correct depth and width and the top sand has been etched away in a square shape for eventual placement of the square shaped concrete lid. It is better to do this now rather than after the soakwell unit is in the ground. Soakwell hole
The soakwell hole in proximity of downspout located approximately 1 metre from foundation.

The trench from the downspout to the soakwell hole which will hold the 90mm PVC stormwater drain pipe has been dug.

The angle only needs to be slight but is actually dependent on how deep the top of the soakwell ends up being.

Because brick paving was to be installed over the drain pipe trench the top of our soakwell ended up being about 25cm's below the top surface of the sand.

The 90mm drain pipe trench

Once our hole and trench are prepared we snap together the two halves of the soakwell itself and "pop" out the hole to receive the 90mm drain pipe.

This soakwell product was acquired from local supplier Bunnings Warehouse and has proven to be adequate for our residential use.

There are other products available including concrete soakwells which are a must for under driveway or other heavy traffic areas.

The 20kg bag of "Blue Metal" stone gravel can be seen against the fence.

Assembled soakwell ready for installation

Here the soakwell unit has been placed in the hole and the drain pipe hole oriented towards the trench.

A little fiddling around is done with the "levelness" of the soakwell unit as well as its depth to get a general positioning for the alignment and inserting of the end of the drain pipe.

This "fiddling" includes the tamping down of the loose sand at the bottom to insure the final depth doesn't change too much due to settling, etc.

Pouring in the "Blue Metal" stone helps with this final positioning adustment.

Soakwell unit placed in hole

Here it can be seen the initial assembling and placement of the 90mm PVC stormwater drain pipe with the right hand end showing the two 45 degree "elbows".

In our experience for simple residential soakwell use it is not necessary to use PVC bonding cement or glue to "seal" where the elbows and pipe meet in fact it has been found that allowing a little "flexibility" in the joined parts of the pipe helps in the final adjusting.

Partially assembled drain pipe

This picture shows the final assembled drain pipe with the grated drain top.

There are several types of "drain tops" that are in use. We use this type of drain top as we've found that in the event of extreme heavy rain the soakwell can fill up faster than it can drain down into the surrounding sand and the water backs up the drain pipe, this open topped drain allows the excess water to disperse across the brick paving etc. rather than "bubble up" through to the top of the surface which can create holes in lawn and sinking which can happen with the traditional drain type shown below because it restricts the backed up water forcing it to "bubble up".

drain top
The drain pipe and drain top assembly inserted into soakwell unit and positioned under the downspout in the trench. drain pipe and drain top set into trench

Once the soakwell unit and the drain pipe assembly are positioned light backfilling is used to hold everything in place.

It is important to only gently tamp and settle the sand back around the pipe so that it is not forced out of position.

Eventually a combination of garden hose watering and tamping down is done to get the loose sand settled and keep the positioning.

Water is also poured down the drain just to insure this simple system will do its job.

drain pipe partially back filled to hold in place
Here is a closeup of the "open grate" drain top type which allows excess water to escape in the event the soakwell backs up due to heavy rain.

Now we begin lightly backfilling around the soakwell unit with sand and Blue Metal gravel. The majority of the Blue Metal gravel has been dumped into the bottom of the soakwell to aid in drainage and inhibit fungus. Filling in the gap around the soakwell with a thin layer of loose gravel is recommended as it will slow the accumulation of sand that may slowly seep into the soakwell.

Note the "squareness" of the top area of the soakwell hole which allows room for the 600mm x 600mm concrete lid. It is good to get this general shape done before getting to this point or you end up knocking the excess sand in and around the soakwell. A little "shaving" of the sand to get the final square needed is usually what we allow to fall around the soakwell in our initial backfilling.

gravel and sand backfilling begins
Here we've backfilled around the soakwell leaving the adequate square shape for the concrete lid. A thin but strong stick or pole (like an old mop handle) is used to "poke" down around the soakwell to help settle the sand and gravel into voids and spaces around the base and sides. We then gave a good spray of water to help settle the sand. soakwell unit backfilled
Here the 600mm x 600mm concrete lid is carefully laid on top and centered. Backfilling then continues.
Here the soakwell drain pipe trench is carefully backfilled and lightly tamped and water sprayed. backfilling drainpipe and soakwell

Here we have backfilled and leveled everything and will continue with water spraying to assist in settling the loose sand. Light tamping and foot traffic over the area helps settle the loose sand.

 

Job completed.

whole area backfilled, smoothed and leveled
 
Soakwell Installation Scenario 2
In the following set of images for an installation at another downspout location it can be seen that the hole had to be carefully dug between some utility and water pipes that ran alongside the house at varying depths. And while it is not recommended, it was decided to run 2 downspouts into the same soakwell in this case as the one downspout did not spill much water from the gutter. The Blue Metal gravel can be seen poured in the bottom to assist in the draining as well as prevent fungus buildup.
Both downspouts can be seen here utilizing the same soakwell. It is common practice to use the drain tops showing so that in the event the soakwell does fill faster than it can drain, the overflow will simply and safely run out over the bricking that would be installed avoiding the problem of overfilled soakwells forcing a "bubbling up" which can loosen and distort any brickwork above.
This view shows the 600mm x 600mm concrete slab cap placed on top to be followed by backfilling.
Here is that same area backfilled, smoothed and watered down to settle the loose sand which fills in any voids preventing any sinking later of the surface. This area was to be eventually bricked therefore a compacting machine would be run over the surface making it important that the sand was settled as much as possible. Running a sprinkler or hand sprinkling as well as natural and other activity caused vibrations in the ground should accomplish the settling.

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