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Types of Water Pipe. What to Use When

I have been helping Kevin fit water pipes for the north wing of our container house. In doing so I realised that there are actually so many different types of water pipe one can use for the plumbing in one’s house. How does one know what to use when? What are the advantages and disadvantages of each type of pipe? I asked Kevin for some insight into the world of plumbing pipes.

The first thing that Kevin said that I needed to know is that each type of pipe has a variety of classes. What class you use would depend on the application. Wow! Plumbing pipes are actually a lot more complicated than you’d think. So, herewith a very basic summary of the most common types of household pipe found in South African homes, and some of their advantages and disadvantages.

Types of Water Pipe

Galvanised Steel

Galvanised steel pipes are not used much in anymore in modern houses. However, this is something you are quite likely to find in an older house. Copper pipes have mostly replaced the galvanised steel ones as galvanised steel will eventually rust. Interestingly, if they are used alongside copper pipes, you have the added risk of galvanic corrosion, (I mentioned galvanic corrosion too, in our article on fitting windows) especially if your water flow is from copper pipes to steel. The reaction is so fast that you’ll be replacing your pipes in a matter of months. However, if your water flow is from the galvanised steel to copper, the situation won’t be ideal, but is better and can be used.

Copper Pipes

copper pipes with compression fittings

Copper pipes have since replaced galvanised steel. A downside of this type of pipe is the price. It’s one of the pricier pipes on the market, but you can expect an extremely long life span for copper pipes. They are also easy to fix, should something to go wrong. Strangely enough, copper pipes can react to the chemicals found in concrete and the pipes can corrode. To prevent this from happening, it’s best to wrap the pipes in something such as paper, if they are to be embedded in concrete. Compression ring type fittings are usually used to join this type of pipe.

(You can read more about compression fittings on our article on repairing damaged water pipes)

Polycop Pipe

Outdoor tap fitted with polycop pipe
Outdoor tap fitted with polycop pipe

This red plastic type pipe is a cheap option. It’s very good for running long distances for cold water only. If the incorrect fittings are used, or it is used for hot water, expect problems. Compression ring type fittings are usually used to join Polycop pipe. If polycop is used for hot water, the continual expansion and contraction of the line will cause the fittings to loosen, which will result in leaks. Polycop pipe can also be welded together. This is a cheap method of joining sections, that has excellent results.

Multi-Layer Pipe (aka MLP, PEX or Composite Pipe)

Multi-layer PEX pipe with plastic insert
You can see the layers on MLP pipe end and on the right is the plastic insert that stops it corroding

This is possibly the most interesting water pipe, with many names. It is made from three layers; two plastic with an aluminium layer sandwiched between them. If this pipe is fitted correctly, it is the best option with almost no disadvantages.

The aluminium makes this pipe bendable. It won’t kink and it keeps its shape once bent. It’s good for underground and in walls. There is no galvanic reaction to be concerned about and it is cost effective. The only issue is that every pipe end must be fitted with a plastic insert before adding the compression fitting. If the insert is not fitted, water can get in between the layers and cause the aluminium to corrode. Over time, the corrosion will cause the plastic to crack and you’ll end up with leaks. This pipe is available in 100m rolls so will have less joins (in comparison to copper, for instance, which is sold in 5.5m lengths).

corroded PEX pipe
This is what happens if you don’t use an insert

HVAC Pipe

There is a plastic pipe that looks similar to the multi-layer pipe (but is grey). However, this pipe is intended for heating, ventilation and aircons. It can handle reasonably high pressure, as one would find in water pipes. Some plumbers do use it in plumbing installations but it is not recommended as there are better options.

Irrigation (HDPE) Pipe

I’m sure you’ve seen this pipe variety. This black plastic pipe is usually used for irrigation. There are certain classes with thicker walls that can be used very successfully for cold water, over long distances, underground. It can also be rolled in coils and placed atop a roof (or other sunny spot) as a makeshift solar geyser. The black plastic absorbs the heat which is then transferred to the water in the coils. It is UV stable enough to be used for this application.

PVC Pipe

PVC waste pipes with HDPE water pipe
Water in (black HDPE pipe), waste out (large diameter PVC pipe)

This plastic pipe is not usually used for pressurised water, although certain classes with thicker walls are available. They can be tricky to fit as they have to be glued together with PVC glue making it difficult to get water tight. You’ll usually find this pipe used for waste and run-off, such as in gutters, basin, bath and shower waste, and of course, your sewerage pipes. As well as various available classes, you get SV, UG and a blue type of PVC pipe. SV pipes are used for soil (waste) and ventilation. They are white and UV stable. UG pipes are for use underground. They are a more yellowish colour and will fade and crack in sunlight. Lastly, the blue PVC pipes are for pressurised water. Council main water lines often use this type of pipe.

Of course, there are many many types of water pipe on the market. There are enough pipes for sale that one could dedicate an entire blog to writing about nothing but pipes. It’s a very unique world.

Whatever types of water pipe you choose, buy a quality pipe that will last. Our South African readers can look for a product that has been SABS approved.

6 thoughts on “Types of Water Pipe. What to Use When

  1. Interesting; You’re right about mixing galvanised fittings in conjunction with copper/brass. Galvanic action occurs with the dissimilar metals and the effect is greatly hastened when in hot water systems. Many years ago in Zimbabwe we had a shower installed, the plumber not having a brass elbow so he used a galvanised one instead. A few months later and the shower was nothing but a feeble trickle, myself having to run around in the shower just to get wet!. I ended up in the roof, taking the copper pipes apart to find out why, even to the extent of looking down through the length of pipe to make sure it was clear. I finally found it, the copper and the galvanised steel had corroded so badly that it was blocking the flow. Fortunately it was right at the hot water shower tap so I could dig the corrosion out with a piece of fence wire. It would have been better to replace the fitting but that would have meant breaking the tiles away for access.

    1. Wow! You must have been really happy when you found the problem and grateful you didn’t end up with a water leak damaging your walls. Thank you for sharing the real life experience.

  2. My goodness, you’re becoming quite the expert on obscure specialisms!

    1. Not quite sure how useful yet

  3. Have a look at the JG Speedfit Range – https://www.johnguest.com/speedfit/products/plumbing-fittings-home/

    We are widely being used in container conversions as well as other ABT’s in South Africa

    Should you be interested, give me a shout on 071 361 0163

    1. Thanks! We will check it out

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