Rainwater Harvesting for Drylands and Beyond by Brad Lancaster

Sealers Approved for Contact with Potable Water

Sealers for concrete and masonry

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Thoroseal
A cement-based, waterproof coating for concrete and masonry. It is NSF approved for sealing concrete or masonry tanks storing potable water. It is also used to seal the concrete base of culvert tanks. To waterproof such a tank it is typically used in conjunction with another product, ACRYL 60, which improves the adhesion of the sealer to the tank. I have used this product to seal precast concrete septic tank cisterns. Thoroseal is manufactured by Chemrex.
In Tucson it is available from Border Products: (520) 623-4100
www.chemrex.com

Cement Slip (aka Cement Slurry or Nil)
NSF 61-certified Portland cement mixed with water to form a thin paste (no sand or gravel added). It is used to seal cement, masonry, and ferrocement tanks. Apply the slip to a 1/4-inch thickness with a trowel on the same day the concrete tank is poured or plastered. Cover the tank with a tarp after the slip has been applied to keep humidity in the tank high and to prevent the slip from drying too fast and cracking. When the slip is firm, but still green, spray it lightly with water or set a bucket of water in the tank to enhance humidity, and cover the tank again with plastic or a tarp. Keep the slip moist and covered (shaded from the sun) for three weeks for thorough curing.

Antihydro and Antihydro R
Admixtures of organic and inorganic chemicals used to waterproof concrete and increase its workability, strength, hardness, and durability. According to the manufacturer, mixing Anti-hydro within a concrete mixture produces impermeable concrete that is hard, non-dusting & safe for potable water.However,  I was not able to obtain information from the manufacturer on what entity approved the products’ use with potable water.
Anti-hydro is intended for use in temperatures below 850F. Anti-hydro R is intended for use in temperatures exceeding 850F. Anti-hydro products are manufactured by Anti Hydro International, Inc.
www.anti-hydro.com

XYPEX HD-150
A concrete waterproofing coating approved by NSF for use in potable water tanks and cisterns. It must be applied to bare concrete only. According to a representative of the manufacturer, XYPEX HD-150 is marketed for homeowners, though it is the same product as XYPEX Concentrate which is marketed to concrete contractors. XYPEX HD-150 is manufactured by XYPEX Chemical Corporation.
www.hi-dry.com/index.html

AMES Blue Max
We do NOT recommend this product for use within water tanks.
It is a blend of adhesive elastomeric liquid rubber. The manufacturer claims it is a new impenetrable rubber technology for waterproofing in extreme wet situations such as flat roofs, below-grade foundations, basement walls, cisterns, water troughs, catch basins, ponds and fountains. However Watershed Management Group in Tucson, Arizona, has found BlueMax does not maintain a seal in tanks. WMG’s Catlow Shipek reports, “When submersed in water it is common for blisters to form as layers separate either from each other or the surface it is applied to. It also seems to re-emulsify slightly.”

Additional notes: Water coming in contact with Blue Max can be expected to have a slight chemical flavor. Also, this product is NOT certified for potable water systems by neutral third-party institutions such as NSF, though the manufacturers claim it is safe for use in potable rainwater catchment systems.
www.amesresearch.com/bluemax.htm

Sealers for gutters and for between different materials such as concrete/plastic and metal

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Sikaflex-1A+
A moisture-cured, single-component, polyurethane-based, non-sag elastomeric sealant which can be used in green and damp concrete applications. Can also be used as an elastic adhesive between materials with dissimilar coefficients of expansion such as concrete and metal or plastic and metal. I’ve used it to seal seams in gutters and seams around downspout pipes entering tanks. It is also used in culvert tanks to seal the seam between the metal culvert and concrete base (after the concrete has been sealed with Thoroseal), and the spiraling seam of the culvert itself. It is USDA-approved and NSF-approved for potable water contact. Sikaflex-1A+ is manufactured by Sika Corporation. In Tucson it is available from Border Products: (520) 623-4100.
usa.sika.com/sikaflex/en/Sikaflex-a1-plus/Sikaflex-1a-plus-Product-Info.html

AMES Blue Max
We do NOT recommend this product for use within water tanks.
It is a blend of adhesive elastomeric liquid rubber. The manufacturer claims it is a new impenetrable rubber technology for waterproofing in extreme wet situations such as flat roofs, below-grade foundations, basement walls, cisterns, water troughs, catch basins, ponds and fountains. However Watershed Management Group in Tucson, Arizona has found BlueMax does not maintain a seal in tanks. WMG’s Catlow Shipek reports, “When submersed in water it is common for blisters to form as layers separate either from each other or the surface it is applied to. It also seems to re-emulsify slightly.”

Additional notes: Water coming in contact with Blue Max can be expected to have a slight chemical flavor. Also, this product is NOT certified for potable water systems by neutral third-party institutions such as NSF, though the manufacturers claim it is safe for use in potable rainwater catchment systems.
www.amesresearch.com/bluemax.htm

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The Umbrella: Winter 2019/2020

THE UMBRELLA: A catch-all of resources, events, media, and more from Brad Lancaster   Rain Planting E-BOOK now available! Rainwater Harvesting for Drylands and Beyond, Volume 1, 3rd Edition now available in E-BOOK format Plant the Rain gifts Get holidays gifts that spread the word and practice on how we can make the world a […]

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