Preparation
Select prep from Step 1&2
How to build your fountai&pond waterproofing kit
waterproofing
pick size and color for SEMCO Liquid Membrane
extra pigment
For submerged applications we recommend to add extra pigment
Fountain & Pond waterproofing
Build your fountain&pond waterproofing kit
Start by selecting the setup that fits your pool surface and waterproofing needs. Then use the prep and application steps below to complete the job with confidence.
Step by step
How to use SEMCO Liquid Membrane for fountains and ponds
Follow these steps for prep, application and cure timing based on the pool surface you are coating. The goal is a clean substrate, even coverage and enough cure time before water exposure.
1
Prepare your space and Gather your materials
• For concrete or gunnite surfaces we recommend our Preparation D in order to remove any mineral deposits or efflorescence from the surface. For this you will need the following cleaners : Nu-Lift Cleaner and Stone Soap
• For fiberglass surfaces it is required to sand the entire surface first with a 60 grit. Afterwards use Preparation B.For this you will need the following cleaners : Power Cleaner and Stone Soap
• If there is constant dampness in the substrate, use Natural Shield first to mitigate the moisture. Let it fully cure first prior to applying SEMCO Liquid Membrane™ .
Ensure your surfaces are fully cleaned and dried. Gather all the products and tools needed for your project.
Helpful Tip
If you need assistance with which cleaners are needed for the Prep, feel free to use our live chat or call us!
2
Fabric Reinforcement
If you have any cracks wider than 1/4", a Fabric Reinforcement is needed to bridge the crack. Any cracks smaller than 1/4" width, SEMCO Liquid Membrane™ can be applied over it.
3
Masking
Mask off areas that are not receiving any coating. Remove masking tape before material has fully cured.
4
APPLYING COAT
Use a 1/2" nap roller. Allow any pre-treated areas to fully dry. Apply a thin coat (0.015 inch per coat) of SEMCO Liquid Membrane™ with brush or roller over substrate including pre-treated areas. Once you can walk on the surface and not get any residue on your shoe or feet or cannot leave a fingerprint impression it is ready to re-coat. Apply another thin coat of SEMCO Liquid Membrane™ in an alternate direction over the first coat of SEMCO Liquid Membrane™. Let topcoat dry to the touch, approximately 1–2 hours at 70 °F (21 °C) and 50% RH. When last coat has dried to the touch, inspect final surface for pinholes, voids, thin spots or other defects.SEMCO Liquid Membrane™ will dry to a lighter color when it’s dry to touch. Use additional SEMCO Liquid Membrane™ to seal the defects. Required total thickness is 0.03 - 0.04 inches for non submerged applications. For submerged applications a min. required total thickness of 60 mil is required. Allow 6-7 days for full cure to filling with water.
Helpful Tip
For submerged applications we recommend adding Extra Pigment for a more solid overall finish
5
Curing Time
Curing time depends on temperature, humidity and airflow, however typically initial cure is within 6 - 7 days as per specific product recommendations.
6
Additional Information
• For clean up use warm water to clean brush or roller right after use.
• For optimal bonding we highly recommend preparing the surface as mentioned above for best results.
• Stir up the product well before use in order to mix up the color pigments.
• Avoid application in direct sun light in the afternoon or temperatures of over 85F as it might cause the product to dry too fast before it can adhere to the substrate
• It can not be applied to wet substrates or substrates still containing moisture, else it will not cure correctly and stay tacky. Max. rest moisture in substrate can be up to 3%. If you are unsure about the moisture content, have it measured prior to application.
• For applications where the product is fully submerged, 3 coats @20mil each is required and allow a curing time of minimum 6-7 days.Also application must coat entire surface to above the waterline.
• Application on non porous surfaces such as metal or fiberglass : Apply thin coats as this will allow for the product to cure faster.
• Cure times are displayed in our curing chart. However if coats have been applied too thick, the surface might feel tacky. This is a sign of trapped moisture. If you have left over product, apply a very thin coat over the entire surface. The surface needs to be fully cured and hard before permitting water.
• For applications where SEMCO Liquid Membrane™ is applied on pool plaster, extended curing times might occur as plaster holds more moisture which needs to breath out first. A slight color change may occur when being in contact with water when the product has not fully cured yet. This however will not affect the performance of the SEMCO Liquid Membrane™.
• It is always advisable to apply a small test patch in an inconspicuous are to ensure adequate adhesion prior to full application.
• If you have multiple containers of SEMCO Liquid Membrane™, we highly recommend to either mix them together or use one container for the last layer to get color consistency.
SEMCO Liquid Membrane FAQ
Can I use SEMCO Liquid Membrane™ to seal a concrete or cement fish pond?
Yes — sealing leaky concrete and cement fish ponds is one of the most loved uses in the reviews. Owners who fought for years with water-stop cement, rubberized paint, and other sealants report the membrane finally sealing cracks and porous cement so the pond holds water. It cures into a flexible rubber layer that bridges the hairline cracks that make old ponds leak.
How many coats does a pond need?
A pond or fountain is submerged, so apply 3 coats (about 60 mils) for a reliable seal, reinforcing cracks and joints with Fabric Reinforcement in the first coat. Build up thin, fully-cured coats rather than a couple of thick ones.
How long must it cure before I add water and fish?
Allow the full cure — 7–10 days depending on temperature and humidity — before adding water, and give it the complete cure before introducing fish. Adding water or fish too early risks blistering and isn't safe for the fish until cure is complete, so don't rush this step.
Can I use it on a waterfall or stream feature?
Yes — reviewers have sealed in-ground waterfall ponds and boulder water features successfully. Coat the channel, basin, and splash areas so water stays in the feature instead of soaking into the cement or escaping through cracks. Reinforce cracks and transitions with fabric, apply the submerged 3-coat build, and cure fully before running water.
How much do I need for my pond or fountain?
Ponds and fountains need 3 coats at roughly 100–150 sq ft per gallon per coat, so measure the interior surface area and multiply for the coats, then add margin — plus the Color Activator and fabric for cracks. Rough or porous stone and cement use more. Tell SEMCO support your pond's or fountain's dimensions and surface and we'll help you calculate it.
What fountain or pond surfaces does it work on — concrete, plaster, cement block, cement bowls?
SEMCO Liquid Membrane bonds to concrete, cement, plaster, and block-with-skim-coat fountains, as well as cast cement bowls. Reviewers have sealed cement fountain basins built from block on a slab, newer plaster garden fountains, and even turned a plain cement bowl into a working water feature. The requirement is a sound, clean, dry surface.