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G4 Pond Sealant

21st Nov 2019

G4 Pond Sealant

Building a concrete pond and don’t want to use a liner? You’ll need some G4.

What is it used for?

G4 Pond Sealant is a moisture-cured polyurethane which forms a non-porous seal on concrete, bricks or porous stone. This makes it ideal for block built and then rendered ponds. It stops any lime leaching from the cement into your pond’s water.


Special Features: Durable deep bonding plastic for concrete with no primer needed

Preparation: You need to make sure the cement render is clean, dry and porous. Highly trowelled surfaces are not advised. You also need to repair any cracks or damaged areas.

Application: Apply with a brush avoiding a really thick first coat. The next 2 coats can be thinned with a G4 thinner and sprayed to apply.

Coats: G4 standard requires 3 coats. All coloured versions need two clear and 2 colour. These must be done ideally between the 60-90 minute mark but no longer than 4 hours.

Drying time: Can be walked on in 60-90 minutes upon final application.

Temperature: G4 can be applied in pretty much all weather conditions, high humidity and temps down to 0 degrees.

Coverage: 550g/sq.m.

Why is it important to stop lime from getting into your pond?

Lime affects the PH of your pond by reducing the acidity, making your pond more alkaline. Making the pond more alkaline will also affect the hardness of your pond water, which in turn will have an effect on the warranty of equipment used. A pond pump that has harsh lime grating over it will not last as long unless properly maintained - as a pump running through soft, clean water.

A UV that has hard water running through it will end up with a quartz sleeve that is covered in lime. Light then can’t emit and this will prevent it from clumping together algae effectively for your filtration system to remove. Therefore, you’ll have a green pond, with unhealthy fish due to the unbalanced PH. Young fish are more susceptible to PH, especially if they are moved from good conditions to poor, their new conditions can cause burning to the skin or chaps.


As their name suggests these lakes are high in sodium carbonate and are considered the harshest of all aquatic environments on earth. Another interesting area to note is the rift valley. Microorganisms here are the main food source for the lesser flamingo - the algae is what actually makes them turn pink! This type of algae is also used in fish foods to help promote colour.