WHY IS MY TANK LEVEL DROPPING?

Step 1: rule out use

This sounds obvious and it is still the most common answer. Reticulation timers, a leaking trough float, a stock valve stuck open, a dripping toilet cistern or a neighbour on a shared line will all empty a tank quietly.

Walk the whole system before you blame the tank. Check every trough, every tap and every automatic valve. On a farm, a single float valve stuck open in a paddock you do not visit can take thousands of litres a week.

Step 2: understand normal evaporation

An open or poorly roofed tank loses water to the air. In a hot, dry, windy WA summer that can be several millimetres a day across the whole surface, which on a large diameter tank is a lot of litres even though the level barely appears to move.

A sealed tank with a sound roof and a lid on the hatch loses very little. If your tank is open topped or the roof has holes, some drop is normal and expected. That is a reason to fix the roof, not the liner.

Step 3: run the 24 hour drop test

This is the test that actually settles it.

• Close every outlet from the tank, including reticulation, stock lines and the house supply
• Mark the water line clearly inside the tank, on the wall, with tape or a pencil mark
• Note the time
• Leave the tank completely alone for 24 hours
• Come back at the same time and measure the drop from your mark

A drop of a few millimetres with a good roof is normal. A drop you can measure in centimetres, with no use, means water is leaving the system. Repeat it over 48 hours if the result is borderline.

Step 4: split the tank from the plumbing

If the test shows real loss, find out whether it is the tank or the pipework. Isolate the tank at the outlet valve closest to the shell and repeat the 24 hour test.

If the level holds with the outlet isolated, the tank is sound and your problem is a buried pipe, a fitting or a valve. That is a plumbing job, not a tank job, and it is usually cheaper.

If the level still drops with everything isolated, the tank itself is losing water.

Step 5: read where the water is going

Once you know it is the tank, the pattern tells you a lot.

• A wet patch at one point on the base usually means a puncture in the liner near there, often from a tree root
• Damp all the way around the base points at a failed base or a low level breach
• Water appearing partway up the wall of a concrete tank suggests a crack, and vertical cracking usually means the bands are letting the wall spread
• A level that falls fast at first and then stops at a certain height means the breach is at that height

That last one is genuinely useful. Note the height the level settles at and tell us, because it locates the damage before we even arrive.

What to send us

When you call, have this ready: - Tank diameter and wall height - Material, concrete or steel - The 24 hour drop measurement - The height the level settles at, if it does - Two or three photos, including the base and the outside wall

That is usually enough to quote the job without a site visit, or at least to arrive with the right materials already on the truck.