Rainwater Tank Leaking? What to Check and How It's Repaired

A wet spot at the base of the tank, or a level that drops when nobody is using water, usually means a leak. The good news is that most leaks start at a fitting, not in the tank itself, and fittings are usually a straightforward repair. Here's how to confirm it and narrow it down.

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1. Confirm it's a leak

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Turn the pump off overnight and mark the water level with tape or a pencil line on a sight gauge. If the level drops with nothing drawing water, the tank or its plumbing is leaking. If it holds, the water is going to the house or irrigation instead. Also rule out the overflow: after a storm, a full tank discharging through the overflow can leave a wet area that looks like a leak.

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2. Check the fittings first

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Look closely at every penetration: the outlet bulkhead, any valves on the outlet, the suction line, drain fittings and the inlet. Gaskets harden and bulkhead nuts loosen over time, especially where a heavy pipe run puts strain on the fitting or where the tank has shifted on its pad. A slow weep at a fitting often shows as mineral staining or algae before you see drips.

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3. The tank itself

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• Steel tanks with a liner, like Pioneer and similar corrugated tanks, hold water in a flexible liner inside the steel shell. A leak there usually means a puncture or a failed seam in the liner. Small damage can sometimes be patched; an aged or widely damaged liner is replaced while the steel shell stays in place.
• Poly tanks can crack from UV exposure, freeze damage or an uneven pad. Small cracks can sometimes be welded, but cracks near the base or on an old tank usually mean replacement.
• Concrete and ferro-cement tanks develop hairline cracks as they age. Many can be sealed with a potable-rated coating once the tank is drained and cleaned.

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4. Look at the pad

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A tank sitting on a pad that has washed out or settled on one side puts stress on the wall, the liner and the fittings. If you see erosion around the base, fix the drainage before or during the repair, or the leak will come back.

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5. Repair or replace?

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It depends on the tank type, its age and where the damage is. A leaking fitting is almost always worth fixing. A liner or tank that has reached the end of its life is often better replaced than patched, because the next failure is rarely far behind. For drinking-water tanks, any repair material that touches the water should be rated for potable use.

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When to call

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If the level keeps dropping and the fittings look dry, the leak is likely in the tank wall or liner, and finding it usually means draining at least part of the tank. We inspect and repair tanks from any brand or installer, and as certified Pioneer installers we know steel liner tanks well. Call (512) 829-5800 or request service online. Tank and fitting checks are part of our maintenance plans.

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