21-day lockdown – Day 12 – Creating a robust irrigation system – Part 1


21-day lockdown – Day 12 – Creating a robust irrigation system – Part 1

Today we’d like to return to irrigation, and discuss one of the key principles behind creating a robust irrigation system – namely high-density pipework. As many home owners can attest to, an irrigation system – whilst convenient – can become a maintenance headache if you are constantly repairing leaks or burst pipes. I was once repairing a client’s irrigation system on their verge when a neighbour walked past – walking his dog – and happened to comment to me, “Ja, those irrigation systems are just a problem!” In another scenario, we were sent a missive by a large construction company who’d heard that we were installing an irrigation system on their site. The document was titled: “Irrigation – an irritation!

Sadly, this seems to be the sentiment of many home owners, who unfortunately have either poorly installed systems, or systems that use low-density pipework. But ask yourself how often you repair or replace the main water lines to your house? Certainly not on a weekly, monthly, or even annual basis. So why isn’t your irrigation system as robust as your main water lines?

In reality, every system requires maintenance or repair at some point in it’s life. Your vehicle is a good example. You might have purchased a very robust vehicle (Grounded uses Toyota Hilux bakkies!), but you still need to service it, as there will always be general wear and tear and parts that need replacing. We’d all love to have tyres and brake pads that last forever, but in reality that simply isn’t the case. There are, however, other parts that shouldn’t need replacing every year, such as your chassis. And this is essentially the analogy I’d like to make with our irrigation systems. Whilst there will be parts that need maintenance or repair from time to time (e.g. moving parts like your popups), the major parts, like your pipework – the ‘chassis’ if you will – should be robust and long-lasting.

So let’s briefly discuss the ‘chassis’ of your irrigation system, the pipework.

20mm low-density (LDPE) pipe (left), and 32mm high-density (HDPE) pipe (right)

At Grounded, we install high-density polyethylene (HDPE) irrigation pipework for our clients, unless otherwise requested, or under circumstances where low-density (LDPE) may be warranted. Typical exceptions are those where a client wants to be able to adjust his irrigation system himself, and therefore the low-density pipework (LDPE) and fittings are cost effective and readily available at garden centres and DIY stores. As the name suggests, LDPE is a lower density pipe, and typically comes in pressure ratings of 3 or 6 bar (referred to in the industry as class 3 or class 6). The fittings associated with LDPE pipes are either nylon insert fittings – which use steel clamps to keep them in place – or “full flow” fittings which attach to the outside of the pipe. These are quick and easy to install, and because a home irrigation system is typically a low-pressure system (<3bar), LDPE pipe has become the norm in these applications.

Unfortunately though, using LDPE pipe can become a costly maintenance expense. In a perfect, uninterrupted world, LDPE would be suitable for a home irrigation system, but the world under our feet is not uninterrupted, and this is where LDPE becomes problematic. An irrigation system is installed in a garden, where there are shrub and tree roots constantly growing and competing with each other. Your LDPE pipes mean nothing to a tree’s roots, which may end up lifting them, or squashing them completely, resulting in leaks or burst pipes, or sprinklers that only dribble water a few years down the line.

The damage done by the roots of an Acacia sieberiana on these LDPE pipes

In the past year we’ve had to repair a number of systems where this has been the problem, and even though it’s only been one pipe, or one tree root, it leaves the home owner with the belief that their irrigation system is a ‘maintenance headache’. But if they’d installed HDPE (high-density) pipes at the start, they would be far less likely to have had these problems.

A home owner in Garstfontein found one day that his pressure pump was constantly turning on and off. This can happen if irrigation pipes have been squashed, because the pump is constantly building up too much pressure, and shuts off for protection. After searching the garden for the fault we discovered these two LDPE pipes that had been squashed by a competing Combretum root, growing through the same hole in the boundary wall

HDPE pipes have a higher-density, and are usually rated between 6-12 bar. They are primarily used for your main water lines, where your municipal pressure may reach these relatively high pressure ratings. To handle that type of pressure, HDPE fittings are also robust, and depending on the application are either compression fittings or clamp-saddles. This means these pipes and fittings can withstand high water pressures within the pipe. But as mentioned above, this is not why we use HDPE for our irrigation systems. Someone might say to you: “you don’t need HDPE for your irrigation system, the pressure is only 3 bar!” And they would be right, but they are only referring to the internal water pressure, and not the external pressures that are present in a garden, such as tree roots.

LDPE pipes (top) squashed/crimped by tree roots. Notice the main HDPE water line (pipe with green stripe) below which was laid in the same trench but was structurally unaffected.

I’m not suggesting that an HDPE pipe is immune to tree roots (we do after all have fig trees that can split rocks!), but installing these pipes gives us a greater peace-of-mind when it comes to the strength and robustness of our irrigation systems.

And what is the difference in cost? Well, HDPE pipe and fittings are of course more expensive than LDPE, somewhere between 3-6 times the price. But in terms of the installation, where the major cost is usually the labour, the cost difference overall is usually no more than 10-20%. Moreover, one needs to temper this with the cost of having to call someone out to repair a leaking LDPE pipe in your garden. It’s not the price of the fittings or short piece of pipe that is costly, it’s the call-out fee.

There are of course many other factors that dictate how robust an irrigation system is, such as the electrical cables, sprinkler choices, the quality of the controller etc., but for now, next time you’re thinking of installing an irrigation system, consider using HDPE instead of LDPE. It might save you many pipe-related maintenance problems in the future.