G4 Clear Pond Seal

(4.9) Based on 5 Reviews


G4 Pond Seal is a moisture-cured polyurethane, which forms a non-porous seal on concrete, brick or porous stone.

G4 uses the moisture in the air and substrate to cure. It is important that the substrate is sufficiently dry to be porous so as to enable the first coat of G4 to bond and obtain a mechanical grip. G4 can be applied in poor weather conditions, high humidity and at temperatures down to 0°C. G4 seals out lime. G4 only provides the waterproof seal. On no account use a P.V.A. based sealer to seal or prime any surfaces. These materials can contain ammonia.

G4 is an excellent sealer for brickwork but below the waterline the brick should also be rendered. The reason is that while the G4 is able to seal hairline cracks it is not capable of bridging larger joints, cracks or holes.

Method Of Application - G4 Standard 3 coats = 550 gms/sqm (for the 3 coats)

1. Ensure the concrete render is dry, (see earlier section) certainly dry enough to be porous.
2. If an old pond, repair any cracks or replace damaged areas, and allow repairs to dry.
3. Ensure surface is clean, any algae is removed, brush off dust and remove loose material.
4. Consumption figures are given in a separate section.

Repairing Cracks In Concrete

A normal cement render mix can be made or there are rapid hardening cements that can be used. When using cements to repair remember that it must be allowed to dry out properly before application of the G4 coating. Alternatively G4 can be used to make an extremely tough repair. Chase out any cracks to provide a reasonable area to fill. Prime with G4 and wait until finger tacky. Mix 6 parts dry fine sharp sand with 1 part G4 (by volume) into a mortar, as dry as possible, consistent with trowelling and using a putty knife or spatula, grout the mix into the crack, leave level. Do not apply in layers thicker than 10mm at a time, if necessary build up layer by layer, leaving a minimum of 8 hours between each application. Very narrow, hairline cracks can be sealed with G4 prior to general application.

G4 Cure (Hardening) 

G4 is mechanically hard after 24 hours and workable on some 6 hours after final application. However, 72 hours must elapse for full chemical cure, before washing down the G4 with copious amounts of clean water. This water should be drained off. The pool can then be filled. Consumption will vary slightly according to the porosity of the substrate. The coverage is based on practical experience gained from many users.


G4 is used to seal waterfalls and from the practical experience of customers it performs satisfactorily.
It is advised that the base of the waterfall is rendered. When dry, apply 3 coats of G4 Pond Seal and allow to harden. The ornamental stone can then be embedded in and grouted. If using a liner on the base, before rendering, then additional time must be allowed for the render to dry, since the render can only dry from the surface.

Before using the user shall determine the suitability of the product for the intended use. This information is offered in good faith but without guarantee or liability. G4 cannot be used to seal over bitumen, P.V.C. or Butyl Rubber linings. It will not bond to the P.V.C. or Butyl Rubber although it will not attack them.

Select Your Options

  • 500g clear

    500g clear
  • 1kg clear

    1kg clear
  • 2.5kg clear

    2.5kg clear
  • 5kg clear

    5kg clear
  • 25kg clear

    25kg clear

Delivery Information

Fast Free Delivery within Mainland UK over £40.00.
Smaller orders under £40.00 are subject to a £4.95 delivery charge. Delivery will typically be made within 2 - 3 working days but may be extended during busy times of the year. Extra charges will apply to certain locations for example Isle of Wight and Islands. In some cases we can even deliver outside the mainland e.g. Channel Isles and arrange the VAT element for you. In all instances please contact us today for a personalised quote.

We Can Offer Next Day Delivery for £6.95.
To meet our deadline for this service you must order before 11.00am to ensure delivery for the next working day. This excludes weekends and bank holidays.

Customer Reviews

Overall Rating 4.9 / 5 Based On 5 Reviews

Delivery 5 / 5
Quality 4 / 5
Price 5 / 5

Excellent service

I've used G4 before, but needed new material for some extensive repairs. The delivery was very prompt - exactly as promised - and i like the way the Company goes out of its way to deal with queries about the use of the material. it is, however, an expensive product !! But there's no other product that is a reasonable alternative. On the advice of a local pond landscaper, i added sand with the mix, and produced an improved colour and texture of finish, which i was very pleased about - but I can't absolutely say whether this will detrimentally affect the life of the product in the long term !!!

By Michael Baldwin.
30th, July, 2018.

Delivery 5 / 5
Quality 5 / 5
Price 5 / 5

Bird Bath repair

Bird bath repair I used this to repair a stone bird bath that used to belong to my parents and had treasured memories. It seems to have worked a treat, the water no longer leaks out of it, so I and all the birds who use it are very happy! Thank you!

By A Price.
24th, July, 2018.

Delivery 5 / 5
Quality 5 / 5
Price 5 / 5


Used to waterproof two terracotta pots for water feature. It goes on very easy and enhanced the look of the pots Now all fully waterproof and installed.

By Robert Pullen .
24th, August, 2017.

Delivery 5 / 5
Quality 5 / 5
Price 5 / 5

pond repair

cannot answer any of the above as the website will not allow me access via keyboard However , the liner was excellent and solved my problem of pond losing water due to faults in the old 20 year old liner which had either become porous over the years or developed pin holes .I simply laid the new liner over the old one .

By peter gibson.
03rd, July, 2017.

Delivery 5 / 5
Quality 5 / 5
Price 5 / 5

Repair of concrete waterfall

We purchased this product as we have a home made concrete waterfall going into our pond, which leaked and emptied the pond during use. We had tried other products which had not worked, but G4 pond seal worked a treat, sealing the unseen cracks in the waterfall - now the waterfall works without emptying the pond!

By Sylvia Jones.
12th, August, 2016.

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