Bladder Tanks

Types of Bladder Tanks:

There are two types of bladder tanks in the market.

Metal Bladder Tanks

are made with a flexible membrane (bladder or diaphragm). I’ll discuss this type later, as it is not usually used in rainwater harvesting systems. Flexible
Bladder Tanks are fabricated from two pieces a rubberized material, with one seam connecting the two pieces. These Rain Bladder Tanks provide a relatively new method of storing water. The bladder remains flat until filled with water, and become flatter as the water is removed. These are usually constructed to hold a very large amount of water, and they are often located under a deck or porch – where they are not readily noticed.

Advantages of Horizontal Flexible Bladder Tanks

  • Very large volume of water can be stored in wasted space, hidden from view – in crawl space or under deck or porch;
  • Can be custom manufactured to fit any space requirements;
  • Free-standing pillows hold up to 40,000 gallons;
  • UV resistant with proven material performance for 20+ years;
  • Lightweight: easily and economically shipped worldwide; and
  • No algae or mosquito issues.

Bladder tanks can be an outstanding answer when lack of room around the house means that above-ground water tanks cannot do the job. Quietly sitting between the supports under your deck, or between the piers under your house, bladder tanks do their job out of sight. But until now, price has been the problem. Prices used to be between $1,000 and $2,000 for single 500 gallon bladder tanks. The new flexible reinforced bladder tanks have raised the bar on quality – with dramatically lower prices. They’re also made tougher and more feature-rich. Now you can have 500 gallon bladder tanks for much less.

Prices for small capacity bladder tanks are still expensive ($295 for 50 gallon; $358 for 100 gallon; $492 for 250 gallon, and $638 for 500 gallon bladder tanks), but the per gallon cost drops considerably for the large bladder tanks ($1.11@ for 1,000 gal; $.73@ for 5,000 gal; and $.60@ for 10,000 gal). This compares to the average $2.40 cost per gallon for most 50 gallon plastic rain barrels. So, if you want to store a lot of rainwater, you may want to consider flexible bladder tanks.

Atlanta’s GreenHaven Showhome features a 3,600 gallon bladder tank, shown to the left, which runs the home’s irrigation system. Only 1/2 inch of rainfall collected from the home’s roof and pervious driveway fills the pillow.

This flexible bladder tank, installed in the crawl space of this home, is “The Original Rainwater Pillow” made by Rainwater Collection Solutions, Inc from Alpharetta, GA. ( The Rainwater Pillow is a flexible alternative to a rain barrel. Able to hold significantly more water than conventional barrels, the “pillow” can be placed underneath decking, in a crawlspace, or any other ground-level hidden space.

The Rainwater Pillow, as with rain barrels, is designed to take advantage of even short rain showers, collecting a large quantity of rainwater in minutes. It does this by directing all the rainfall from the guttering system of your house, using gravity, into the pillow through wide piping for fast collection. Two overflow pipes ensure that the pillow will never overfill or rupture.

By collecting free rainwater you can reduce your household water bills (especially if on a water meter) as the water can be used for your lawn and garden, and cleaning cars and other outdoors objects. It also helps to reduce the amount of water entering storm drains, reducing the required processing in water treatment facilities. Another significant benefit of collecting rainwater it that it be used in times of drought when water restrictions are applied – so your lawn and garden can thrive.

The 1,000 gallon Original Rainwater Pillow system installed in the home’s crawl space, shown above, will be used to drip irrigate all the trees and shrubs. The system will collect approximately 600 gallons for water from one inch of rainfall. With an average annual rainfall of 57 inches, 34,000 gallons of water can be collected and used.

The Rainwater Pillow comes with all the basics needed for installation on your property, including a 25 psi water pump. This pump can provide 10-12 gallons of water per minute, which is comparable to a standard hose attached to a tap. The pump is controlled by a remote control so you are able to water your garden, green house or even wash a car, by pressing a button.

The pillows come in a range of sizes. The standard basic size has a 1,000 gallon capacity, but there are pillows for up to a 40,000 gallon capacity. The Rainwater Pillow can be made to custom specifications to allow them to fit in any available ground level space like that within a crawl space, under decking, or in a greenhouse. The standard 1,000 gallon pillow measures 9 ft x 11 ft x 2.5 ft and needs a clearance height of at least 3 ft to accommodate the pillow expanding with water.

The rainwater pillow starts at $2,500 for a 1,000 gallon “Kit” and tops out a $16,000, for a 40,000 gallon pillow.

The pictures above show a water bladder tanks under decks – one under construction and one finished. Every part of the system that can come in contact with your home’s interior is completely sealed. According to their guarantee, no moisture from The Original RainwaterPillow will leak, evaporate or otherwise enter your home.

Another source of bladder tanks can be found at This 250 gallon tank shown to the left can be purchased for less than $500.00. You can find a wide variety of bladder tanks at Flexible water bladder tanks are used for the storage of potable water for indoor and outdoor applications and are ideal for use in low ceiling areas such as crawl spaces and under deck areas where conventional plastic tanks are too tall.

This picture to the right shows an elaborate rainwater storage system using a large flexible bladder tank. This picture was found in the second article in a 6 part series on“Saving Water” by Scott Bird. Living in Sydney, Australia, Scott is acutely aware of the value of this precious resource.

Newer homes often take advantage of the massive, inflatable bags which are designed for use under floors or decking. Although it’s possible to install these in existing homes, it’s much easier (and cheaper) to design the floor with the bags in mind.

Collapsible “Rain Barrel”

A variation of the flexible rainwater bladder tanks is a Collapsible “Rain Barrel”. The collapsible rain water barrel is becoming an increasing popular choice for people. Rain barrels that collapse are usually made from PVC resin and have an inner mesh bag. Some collapsible barrels are made of a durable polyester material and a variety of plastics. They are light weight, easy to move, easy to store, and affordable.

This green 52 Gallon Knock Down Rain Water Barrel, shown to the left, is a hybrid– between a flexible water bladder and a standard rain barrel. It’s a durable, weather-resistant nylon barrel that collects up to 52 gallons of rain runoff from your home’s gutter spout and filters debris. Simply attach your garden hose to the tap at the bottom of the barrel and water away. The barrel itself conserves space, as well – when you want to store it during the winter, just collapse it, move it easily, and store it neatly in a shed or garage. You can find this Collapsible Rain Barrel here.

Metal Bladder Tanks

The other bladder tank mentioned earlier is a metal tank, not normally used for rainwater harvesting systems.
The illustration to the right shows a metal bladder tank with a flexible membrane (bladder or diaphragm) within the tank. This bladder separates the water and air within the tank. After water is placed into the tank, the air within the flexible membrane is put under pressure with a pump. This allows the water to be forced out at pressures greater than gravity would produce. These tanks are commonly used in industrial applications and are not normally used in rainwater harvesting systems because of cost and installation complexity.

How Metal Bladders Tank Get Refilled:

With metal bladder tanks, as the water and air pressure get low when water is released, a pressure switch sends an electrical current to a water pump. This water pump, which may be connected to another water source (well, lake, etc.), causes the water pump to kick on and pipes water back into the water bladder tank. As the bladder is filled, the water pressure and air pressure rise back to their normal levels. After the water pressure and air pressure are back to normal, the contacts within the pressure switch are pulled away from each other. Once the pressure switch stops supplying power to the pump, the water pump stops pumping water into the tank. This process begins again each time water is removed from the metal bladder tank.

Description: Flexible Bladder Tanks are fabricated from two pieces a rubberized material, with one seam connecting the two pieces. The bladder remains flat until filled with water, and become flatter as the water is removed. These are usually constructed to hold a very large amount of water, and they are often located under a deck or porch – where they are not readily noticed.