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FLEXIBLE LINERS FOR WATER TANKS

TECHNICAL DIGEST




Tank liners are an easy and inexpensive solution to a broad range of storage tank problems. The liners can be used in new tanks or in existing tanks that may be considered unusable. This includes tanks made of CONCRETE, WOOD and STEEL. The tanks need not be liquid tight, only structurally sound.

COST FACTORS

Cost of the liner depends on the size, the type of material (vinyl, rubber, urethane, etc), how thick the material is, whether it is unsupported or supported, potable grade or industrial grade material, whether it can be manufactured as a one piece liner or in sections and whether additional welding processes are required such as a top hem or shrouds to slide over pipe fittings.

As you can see, there are many variables to consider resulting in a wide price range. Once we determine your specific requirements, we can make recommendations and quote on the liner, supplies, shipping costs and/or installation.

WHAT IS NEEDED IN ADDITION TO THE LINER?

plumbing

The type of tank and how it is plumbed will determine the additional installation supplies that will be needed.

Generally, the plumbing needs to be changed in order to achieve a watertight fit to the liner. Also you need a way to attach the liner to the inside top perimeter of the tank. In some cases, a geo-textile membrane will be recommended to cover cracks in concrete tanks or protruding bolts in metal tanks. We can supply all your needs once we determine what they are.

HOW TO DETERMINE WHICH LINER MATERIAL TO USE

Material to be used will depend on several factors:

Any tank that is used as a source for drinking water must use potable grade material. This material is formulated with FDA sanctioned raw materials and complies with EPA requirements for potable water storage.

Potable grade material is also recommended for water garden and fish pond liners. Aquatic life can be very sensitive to water purity, taste and odor.

Industrial grade material is for non-potable use only. Some materials may be specifically formulated for containment of gas and oil products, other materials may be manufactured to handle elevated temperatures.

We will be happy to discuss your particular needs and make recommendations based on information supplied.


LINER RECOMMENDATIONS FOR DRINKING WATER SYSTEMS

In WOODEN TANKS..........

In the early 70's we began lining redwood storage tanks in Northern California's "redwood country". Water storage tanks made from the mighty redwood trees are common in this part of the country and many tanks range in age from 10 years to 100 years old. Redwood tanks will eventually leak due to fluctuations in water levels throughout the years. People have tried many methods to plug the leaks...tar, cloth, wooden plugs, redwood sawdust, rocks...these methods are not recommended and most methods do not work. Liners do work and it is an affordable way to add many additional years to the life of the tank.

We recommend 20 mil PVC simply because it is more permeable. The small amount of water that permeates through the material keeps the wood slightly damp on the inside of the tank. Thicker material, such as 30 mil PVC, is also suitable.

Hypalon or any reinforced or semi-rigid material is not recommended because they lack the elasticity to conform to variations in the wood.

Wood staves will shrink to some degree depending on location and exposure to sunlight. As a regular part of your tank maintenance program the tank should be checked occasionally and, if needed, the bands tightened.

For information on new redwood tanks and related supplies, contact the following:

  1. T E BROWN INC
    14361 Chapman Rd
    San Leandro CA 94578
    tp#510-357-4840 fax#510-357-9957

  2. Bellagio A Wood Tank Co
    12786 Old Redwood Hwy
    Healdsburg CA 95448
    tp#707-433-4605 or call toll free at 1-800-707-8265
    fax#707-433-9214

liner installation in concrete tank

In CONCRETE TANKS and RESERVOIRS.........

In concrete tanks 30 mil PVC is recommended since it is far less permeable than 20 mil PVC but either material can be used. Hypalon will be recommended if any of the following conditions exist:

A geo-textile underlayment material should always be used to protect the liner if the inside of the tank is cracked or rough.

After installation has been completed, seal the exposed geo-textile at the top of the tank with a bead of silicone around the entire circumference. If this step isn't performed, condensation will form on the tank walls and seep out through the geo-textile.


metal tank

In METAL TANKS..........

In smaller metal tanks any of the materials are acceptable. Hypalon will be recommended for the larger tanks or if any of the following conditions exist:

Metal tanks need to be cleaned then coated with a rust inhibitor. We highly recommend that a geo-textile underlayment be used between the tank and the liner to help insulate the liner from heat and cold transmission through the metal and to protect the liner from any chemical migration from the rust inhibitor. When installation has been completed, seal the exposed geo-textile at the top of the tank with a bead of silicone around the entire circumference. Weep holes should be drilled in the bottom of the metal tanks to allow for release of condensation.

***ALL MEMBRANE LINING MATERIALS TRANSMIT WATER VAPOR TO SOME DEGREE.***

BEFORE YOUR TANK IS LINED, INSPECT IT AND MAKE NECESSARY REPAIRS

Begin with a visual inspection, look for obvious problems.

In wooden tanks, woodpeckers can damage the outside of the tank. Minimize the damage by stapling a fine plastic coated screen to the outside of the tank.

Dry rot is a fungus that causes wood to crumble. It can work away at the wood so inconspicuously that it can easily escape your notice. If you find evidence of dry rot, termites or other bug damage, consult a licensed termite inspector or pest control professional. Termites will eat through redwood, especially the older redwood where the tannins have been leached out from years of use. If the damage is extreme, the staves should be replaced or reinforced before lining the tank.

Repair leaking roofs and torn screens.

Old wooden ladders should be removed from the inside of the tanks. In most cases they are extremely unsafe.

IT IS EXTREMELY IMPORTANT, IN BOTH WOOD AND METAL TANKS, THAT THE AREA AT THE BASE OF THE TANK BE KEPT CLEAN OF DIRT AND DEBRIS. DETERIORATION OF THE TANK COULD BE ACCELERATED IF ALLOWED TO ACCUMMULATE.

Large cracks in concrete tanks should be filled with caulking. Small cracks can be ignored. The liner and geo-textile underlayment will work fine without having to do any major repair work.

Metal tanks should be cleaned and painted with a rust protectant. In areas that have rusted completely though the tank, repair can be made by bolting a metal plate over the weakened, damaged area to reinforce it before lining.

Coated metal tanks, if the coating is still in fair condition, can have a liner installed over the coating. Exposed area of the tank can be painted with a rust inhibitor and a geo-textile underlayment is recommended.

ARE LINERS EASY TO INSTALL?

There are very few tanks that are exactly the same in construction and plumbing, consequently, written instructions given by the manufacturer can only be in general terms.

Depending on the size of the liner, installation may take only a few hours by a couple of installers or several days to a week with a number of installers. Gererally two people can install a medium size liner (8' diameter x 8' high) in approximately four hours.

Professional installation is recommended if the tank is... center roof support post plumbing

New World offers toll free telephone assistance to anyone wishing to do their own installation in smaller tanks. Call toll free 1-800-523-8853, Monday through Friday, 9 a.m. to 4 p.m.

CAN LINERS BE MANUFACTURED ANY SIZE?

New World can fabricate any size liner in one piece, however, two or more sections or a split liner (open on one side and across the bottom to the center post) would be required if there is a permanent, non-moveable center post. Occasionally, large liners may be fabricated in several sections due to weight and handling problems.

Large liners manufactured in two or more sections will be completed during the installation procedure using field seaming techniques which may include the use of solvents and glue.

It is recommended that the liner air for a period of at least one full week whenever solvent and glue is used during the installation process to allow for dissipation of solvent and glue residue.

Medium and large liners are rolled in a fashion which allow them to be "snaked" into the tank through the existing manhole.

A boom truck is used to lift liners heavier than 250 lbs.

WHAT ABOUT PLUMBING AND INSTALLATION SUPPLIES?

Your requirements will vary depending on the type of tank and the type of liner. We can supply tank nipple kits with FDA recipe soft washers (all of the ingredients in the soft washers have been listed as approved by FDA in 21 CFR 177.2600 for repeated food exposure), attaching bars of stainless steel or high density polyethylene plastic (HDPE), custom fabricated stainless steel or HDPE ring kits, nails, anchor bolts, nuts and washers, silicone, etc.

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