Guide
HOW LONG SHOULD A TANK LINER LAST?
A liner does not usually wear out. It gets punctured, cooked or worked to death. Here is what changes the number.
Short answer
How long does a water tank liner last?
A properly installed tank liner generally lasts about fifteen to twenty years. Steel tank liners sit at the lower end and concrete tank liners with geo-textile matting at the upper end. Tree roots, a rough base, exposed UV edges and a moving tank wall are what cut that short.
The detail
What actually determines liner life
Liner material has a design life, but almost no liner in Western Australia dies of old age. It fails because of something in the tank. That is good news, because most of those things are preventable.
Realistic life expectancy
What we see in the field, on tanks we have lined and come back to: - Steel tank liner, well installed on a clean screeded base: 12 to 20 years - Concrete tank liner over geo-textile matting: 15 to 20 years, sometimes more - Any liner installed straight onto a rough or contaminated base: 3 to 8 years
That last line is the important one. The gap between a good install and a rushed one is not ten percent, it is a factor of three. Preparation is most of the job.
Cause 1: tree roots
Roots are the single most common liner killer we see, especially in the wetter parts of the state. A root finds the moisture under a tank base, grows toward it, and pushes up through the sand until it presses a hole through the liner.
Cutting the visible root and dropping a new liner over the top is a waste of money. The root regrows and does the same thing again. The tree, or at least the root path, has to be dealt with, and the base has to be dug back to clean sand.
Cause 2: a poor base
Everything under a liner eventually prints through it. A stone in the sand base becomes a wear point. A ridge becomes a fold. A rough concrete edge becomes a cut.
This is why we screed steel tank bases flat and free of stones, and why we fit geo-textile matting to concrete walls and bases. The matting is a cushion between hard, sharp, cracking concrete and a flexible sheet. It is not an optional extra, it is the reason the liner reaches fifteen years instead of five.
Cause 3: UV on the exposed edge
The liner above the water line is exposed to sunlight and heat. In the Mid West, the Wheatbelt and the Goldfields, tanks run low every summer, so a wide band of liner is baked for months each year.
UV makes liner material brittle. Brittle liner cracks at the fold line, and the fold line is right where the level sits. That is why we cap and shade the top edge properly, and why a tank that is habitually run near empty ages its liner faster than one kept part full.
Cause 4: a moving tank wall
A concrete tank with slack or corroded bands spreads under load. The wall moves a little every time the tank fills and empties, and the liner is worked at the same points over and over.
This is why we always do band work before liner work. Fitting a new liner into a tank that is still moving is spending liner money to buy a few years. Fix the structure, then line it.
Cause 5: pests and mechanical damage
Termites and ants nest in warm, damp tank bases and leave fine pinholes that are almost impossible to see and very effective at draining a tank.
Mechanical damage is the other one: someone dropping a pump into the tank, dragging a ladder across the base, or overtightening an outlet fitting. If you have to go inside a tank, take your boots off the grit and do not drag anything across the floor.
How to get the full term
Practical things that add years: - Deal with trees near the tank before you re-line, not after - Insist on matting or wall felt, and check that it is in the quote - Keep the roof sound so UV and debris stay out - Fit and maintain insect mesh on the vent and overflow - Fix band tension before it becomes wall movement - Do not habitually run the tank down to the base - Look inside once a year and check the water line and the base
None of these are expensive. All of them are cheaper than a liner.
At a glance
LINER LIFE BY TANK TYPE
Field experience across WA. Your result depends mostly on the install and the base.
| Tank type | Typical life | Main risk |
|---|---|---|
| Steel tank, screeded sand base | 12 to 20 years | Tree roots and pests |
| Concrete tank, geo-textile matting | 15 to 20 years | Wall movement, band failure |
| Any tank, no matting or felt | 3 to 8 years | Abrasion and puncture |
| Tank run near empty each summer | Shorter at any type | UV on the exposed edge |
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