Often in building work, the person installing the piping may be the last person to touch it for a very long time as it's hidden away in walls and ceilings or buried in the ground or under floors. For that reason, it pays to give some thought to the requirements around installing pipes that may never be seen again.

The New Zealand Building Code specifies how long our buildings and parts of them need to last and these are set out in clause B2 durability.

NZBC B2 requires that building elements that are difficult to access or replace, or which would go undetected during normal use and maintenance if they failed must continue to satisfy the performance requirements of the Code for the specified intended life of the building.

A building element is any structural or non-structural component or assembly incorporated into or associated with a building and includes fixtures, services, and drains. The specified intended life means the period of time for which the building is proposed to be used for its intended life as specified in the building consent. For most new building work, this is 50 years

What this means is that some of the parts of a building must be guaranteed to last that full 50 years if they cannot be easily accessed or replaced.

For the plumber’s gasfitters and drainlayers that raises a couple of questions;

• What types of building elements are difficult to access or replace?
• What building elements would go undetected during normal use if they failed?

The obvious answer is any hard to access pipework that is difficult to replace. This can be pipes cast into concrete, under slabs, or installed in a masonry cavity that is not a duct. It also includes any septic tanks built under the structure of a building.

It doesn’t include pipes and fittings behind wall linings or valves that are concealed or moderately difficult to replace. But these elements must still satisfy the performance requirements of the code to last for not less than 15 years.

Plumbers, gasfitters and drainlayers all install pipes in buildings where the access to replace is difficult or they won’t be detected if they fail. For that reason, the pipes need to be installed so that they won’t fail.

Acceptable Solutions in the NZBC provide a means of ensuring the pipework installed beneath buildings meets the 50-year requirement in B2.

The legislation about the hard to access pipes can give slightly differing requirements depending on whether the pipe is for water supplies, foul water or gas. But there are some common themes between all of them.

One of the most important themes is that the pipes are sleeved or wrapped when passing through or are embedded in concrete. This is not only to protect the pipe against damage but also to provide for thermal movement.

Another theme is that any jointing should be kept to a minimum. Or in the case of multilayer gas pipe systems, without any joints at all.

The angle that pipe passes through a slab or foundation is also another consideration. As an example, both G13/AS2 and AS/NZS 3500.2 require pipes passing through a concrete slab to rise at right angles. For a drain passing through a footing, the angle in the horizontal plane should be not less than 45°.

Some solutions require that pipework is tested prior to being concealed. But it is always good trade practice to do this anyway for all of our pipework whether it is a requirement or not.

So if you are going to be the last person who will be able to get at or lay eyes on something you are installing, get it right by making sure you follow the requirements to make it last.