How to repair a leaking water tank or water butt
Instapatch can seal cracks and holes in water butts, rainwater tanks and other tanks that don't hold drinking water.
Where not to use it: Don't use it inside a tank that holds mains or drinking water, such as a loft cold water tank fed from the mains. UK water regulations require materials in contact with mains water to be suitable for it, and the datasheet doesn't state that approval.
What you'll need
- Instapatch Standard patches big enough to cover the damage with room to spare. The order wizard will suggest a size.
- UV Curing Primer and a brush. We recommend primer for tank repairs.
- Scissors or a sharp knife
- Gloves and protective clothing
- Surface cleaner and clean cloths
- A UV lamp or torch if the repair is in shade or indoors
Before you start
- Empty the tank to below the damage, then let the area dry completely.
- Work from outside the tank where you can. Don't climb into a tank to make a repair.
- Only use the patch where there's good ventilation.
- The surface must be free from dust, grease, waxes and loose material.
- Only open the patch when you're ready to use it. It can start to cure within minutes in daylight.
Steps
Clean the area around the damage, remove any loose material or algae, and let it dry.
Brush UV Curing Primer over the area and let it dry fully.
Shape the patch with scissors while it's still in its packet.
Peel the release film from one side, press the patch over the damage straight away, and mould it to the shape of the tank. Apply firm pressure all over.
If you want to paint the repair, peel off the top film now for a matt finish. Leave it on for a gloss finish that can't be painted.
Leave the patch to cure. Keep pressing the edges down until it hardens, so the corners don't lift.
Refill the tank only once the patch has fully hardened.
Cure timing for this surface
Outdoors, daylight cures the patch in 15 to 45 minutes, depending on how bright it is. In a shed or garage, use a UV lamp or torch.
After the repair
Once it has hardened, the patch is waterproof and highly resistant to weather and UV. If you removed the top film, you can paint it.
Common questions
Yes. Instapatch Standard works on plastic, and we recommend primer for tank repairs.
Not if the tank is fed from the mains or holds drinking water. See "Where not to use it" above.
Common mistakes to avoid
- Patching a surface that's still damp
- Refilling before the patch has fully hardened
- Using it in a tank that holds drinking water
- Working inside a tank with poor ventilation
Safety
Wear gloves and protective clothing, and only use Instapatch in a well-ventilated area. It contains polyester compound and styrene, which can irritate the eyes, skin and lungs. If it gets in your eyes, rinse them straight away with plenty of water and get medical advice. If it gets on your skin, wash it off with soap and water.
Storing spare patches
Keep unused patches on end in their original wrapping, somewhere cool, dry, dark and frost free. If a patch is very cold, warm it before use.