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PLUMBING CONNECTION
SUMMER 2016
Then there is the issue of clay plugs and lagging, which
Marco believes most plumbers are unaware of.
“Clay plugs have been mandatory for years and it
seems nobody knows about them. We had a big drainage
contracting business for years and didn’t know about it
ourselves, until we got into this game,” Marco explains.
“Whenever you build a house and dig a trench for the
pipe work, whether it is exiting from underneath the slab
or whether it is going through the edge beam of the slab,
AS2780 states that you must fill that trench from the base
of the trench line, all the way to the top and 300mm out with
compact clay soil. That’s what they call a clay plug. It stops
the ingress of water from getting underneath the slab.
“As soon as you put a trench into the ground that goes
underneath the slab, that instantly aerates the soil and
the moisture can go back down the trench line and get
underneath the slab and cause heave.”
Lagging is often overlooked too, again, due to a lack of
awareness.
“If your pipe work goes through an edge beam of a slab in
moderate H1 soil, you have to wrap it with thick lagging such
as closed sealed polyethylene that won’t absorb water. You
need 20mm thick lagging around any pipe coming out of an
edge beam on the horizontal. That’s to stop the water from
getting in under the slab. In H2 soil that lagging has to be
40mm thick. This is also outlined in AS2780 which a lot of
plumbers are unaware of.”
JOINTS AND FITTINGS
To combat the effects of reactive soils, two Australian
companies in Plastec and Storm Plastics have developed
and supplied the market with a range of expansion, swivel
and combination joints that can be installed either vertically
or horizontally and allow for soil movement without damage.
With that in mind, it pays to do your research to ensure you
have the right tools for the job at hand.
Both manufacturers provide suggestions for drainage
layouts which can be adapted to suit the particular job
at hand, provided all solutions meet AS2780 and the new
deemed to satisfy provisions that will be included in AS/NZS
3500.2 and Section 4 of AS/NZS 3500.5.
CLAY PLUGS HAVE BEEN MANDATORY
FOR YEARS AND IT SEEMS NOBODY
KNOWS ABOUT THEM.
Working in reactive soils requires forethought and the right
gear to avoid the implications of shifting soils.
REACTIVE SOIL