Chicago rooftop water tank (C) Daniel Friedman Rooftop Water Tanks, Cisterns & Free-Standing Water Storage Towers
Rooftop water tank types, materials, properties, history

  • ROOFTOP WATER TANKS - CONTENTS: Types, Uses, Installation & Troubleshooting of Rooftop water storage tanks, Rooftop cisterns & Rooftop water storage fed by municipal water supply or private wells and pumps. Using Pressure boosting pumps on gravity-operated rooftop water tank systems. Water storage tank & tower codes & standards. Water storage tanks, cisterns, rooftop tanks, open tanks, water pressure tanks, steel tank, wooden water tower tanks.
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Rooftop & tower-mounted water storage tanks:

This article describes rooftop water tanks and cisterns and tower-mounted water storage tanks, where they are used, how they work, and the use of booster pumps to improve water pressure in buildings with rooftop water storage tanks.

We include water tower design considerations, codes and standard references & citations. We also discuss using a booster pump to improve building water pressure in buildings with weak municipal water pressure or a weak rooftop. Shown at page top, a rooftop water tower in Chicago. This tower illustrates a traditional woood-stave water tank design that has been in use for more than 100 years.

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Rooftop Water Tanks, Water Towers & Other Water Storage Systems

Photograph of a rooftop storage tank in Mexico

Rooftop water storage tanks In some areas, Mexico, for example in our photo (above-left), rooftop water reservoirs are supplied intermittently with water from a water main in the street.

[Click to enlarge any image]

In cities where the municipal water system delivers functional flow and pressure rooftop water tanks are commonly used on buildings that are six stories or greater in height to collect and then deliver water at functional pressure to the floors below.

But in much of the world even single story structures may make use of a rooftop water storage tank, usually elevated above the rooftop by another meter or two, to deliver functional water pressure to the plumbing fixtures located in the building below. It is the added height of the water tank (or in communities, the water tower at heights over 100 feet with a large tank serving the community) to deliver water at pressure.

The rooftop water storage tanks in this photograph from San Miguel de Allende in Guanajuato are being used both to accumulate a water reservoir so that water is always available to the building, and to supply water at a useful pressure.

Our page top photograph of large rooftop water storage tanks was taken in Manhattan.

Rooftop storage tanks atop tall buildings have been in use for hundreds of years - the water tank shown at page top was constructed of wood with iron bindings and is used to provide good water pressure to fixtures in the multi-story building it serves. In our photos below we illustrate both single and multiple rooftop water storage tank installations observed in Manhattan and in Brooklyn, NY

Photograph of a rooftop storage tank in Manhattan

. In New York City elevated water towers such as those shown above below have been in use since the late 1800's. - The New York Times (2014).

Photograph of a rooftop storage tank in Manhattan

See additional water storage tank details at WATER TOWERS

Also see CISTERNS.

Rooftop water storage tank support construction need to consider these design points:

Photograph of a rooftop storage tank in Manhattan

Weight of a Wooden Rooftop Water Tank (with many assumptions)

Reader Question: how much does a 16 ft. x 16ft. wood water tank weigh?

2016/03/17 Ray said:

how much does a wood andersonville water tank weigh 16h x16w dry


I cannot say for sure since I don't know what Anderson water tank tank you are describing. Are you referring to a specific water tank such as the Anderson wooden water tank / tower built in 1927 and removed in March, 2014? This tank was removed from the Swedish American Museum in Chicago.

But we can get a ballpark estimate of the weight of any wood structure if we know its dimensions and the thickness of wood used. The weight of wood varies by wood species. Wooden water towers are still made by several manufacturers, depending on where in the world the wood water towers/tanks are required. In New York City Rosenwach (in business since the civil war in the U.S.) and Isseks Brothers (in business nearly 60 years) make wooden water towers or tanks, typically in 10,000 gallon size. American Pipe also produces wood rooftop water tanks for NYC buildings.

From what I've read, rooftop water tanks often use redwood so we'll use that for our wood rooftop water tank weight calculations.

Let's "unroll" your 16'x16' redwood water tank and assume these dimensions:

By your quote of a tank that is 16 ft w I assume means 16 ft. (round) diameter water tank. Converting a 16 ft. diameter to circumference gives us about 50 ft. (pi x diameter = circumference).

Let's add a flat tank bottom (pi r2 = area of a circle) of the same diameter (r = radius = 1/2 diameter)

If the top were flat we'd use another 200 sq. ft. (though I bet the top of your water tank is a cone so I'll use a larger area of 300 sq. ft. for your water tank's top).

Adding those up we get

Now we need the tank thickness: Let's assume our redwood is 1 5/8" thick (that's pretty common thickness for water tanks).

We need all of our wood in the same units. 1 ft = 144 sq. in.

Let's now get the cubic volume of our whole wooden water tank (surface area x wood thickness)

Let's now convert our cubic inches back to cubic feet: 1 cubic inch = 0.000578704

Weight of the Empty 16 ft. x 16 ft. Redwood Water Tank

Now let's weigh our cubic feet of redwood: At about 28 lbs per cubic foot that's

Weight of the 16 ft. x 16 ft. Redwood Water Tank Filled with Water

et's fill up your wood water tank and weigh it. The volume of a cylinder is pi * radius2 x height so our water tank will hold, if filled to the brim,

Weight of a Water-Filled Rooftop Water Tank

So our full water tank, before weighting its supporting structure or roof covering, pipes, nails, ladders, scaffolding and other nice features, weighs - if my math is right. If it's not I trust some readers will help me out

Rooftop Water Tank Construction Standards & References

Plastic & Fiberglass Water Storage Tanks - HDPE Tanks

Reader Herman Voegel has pointed out that an up-and-coming area of storage containers includes spun-plastic tanks.

Plastic water storage tank (C) Daniel FriedmanSpecifically, new storage tank types include High Density Polyethylene (HDPE), currently available as tank storage for water, chemicals, waste oils, etc..

The plastic water tank in our photo (left) is used on ground level or on rooftops.

See details at   PLASTIC CONTAINERS, TANKS, TYPES for details about using plastic tanks or containers for water storage.

General HDPE containers come in all shapes and sizes and are quite rugged and relatively cheap compared to using typical 12-gauge steel home heating oil tanks.

The ruggedness of HDPE plastic containers comes from their material density which is typically at a minimum specific-gravity of 1.7, and for heavy-duty at 1.9.

These tanks may be used for storing certain liquids besides water. But home heating oil has not yet been approved for storage in HDPE tanks, basically for two reasons:

  1. UV (ultra-violet) light degrading HDPE plastics over time, making them weak, and
  2. Problems with slight permeation seepage through their plastic walls.

However, fixes have been put in place to properly address these problems. UV-light is checked by using special color additives that prevent their light from penetrating and degrading the plastic walls. Permeation or seepage of oil through container walls is checked by coating them with fiberglass.

Unfortunately, even with these fixes, HDPE plastics for heating oil storage have yet to be universally approved and accepted.

Readers should also see PLASTIC CONTAINERS, TANKS, TYPES where we describe health and other concerns involving plastic tanks and other containers used for water storage.

Attic Water Storage Tanks or Attic Cisterns

Photograph of an attic expansion tank for a heating boiler

Attic Cisterns or water tanks are installed in some buildings to perform the same function as rooftop-mounted water tanks. I don't consider these "rooftop" water tanks but rather "under the rooftop" or "beneath the rooftop" water tanks.

Other smaller attic containers that look like a water reservoir may have been just an expansion tank for the heating boiler system. Cisterns in basements or attics are an open-type water storage reservoir found indoors, and are discussed further at CISTERNS.

A cistern was generally placed where it could be fed by gravity from roof or surface runoff, but any indoor open topped reservoir of water could be called a cistern.

See SOLAR WATER HEATER ANTIQUE for another example of an attic water storage tank.

Water storage may not be on the rooftop nor in the attic. Cisterns or other water storage containers are often located in the basement or courtyard of buildings where they collect rainwater for future use. In the U.S. cisterns were often located in the basement of a (pre-1900) home.

See details at CISTERNS.

Rainwater Storage Tanks & Cisterns

Rainwater holding tank for a passive solar home (C) Daniel Friedman

In a seasonally damp climate such as New York, an in-use basement cistern would certainly be a likely source of unwanted building moisture and would thus be a risk for problematic mold growth.

In arid areas such as the U.S. Southwest and parts of Mexico, very large cisterns are often placed in a courtyard where they collect rainwater for use during the dry season. The above-ground water cistern storage tank shown in our photo (left) is located in Mexico and is discussed

Rainwater for this cistern is collected from a near-flat rooftop [photo] and channeled to a large fiberglass holding tank - the blue tank in our photograph, (above left).

Piping also permits directing water into this tank from a well-fed cistern located atop the concrete block tower [photo].

The tower's height provides water pressure to the building. Currently water is taken out of the bottom of this tank by a simple tank drain valve and hose attachment; to supply this water upwards to the building plumbing fixtures or perhaps to the cistern, a small electric pump will be installed. See rainwater collection and storage cistern details

Water Pressure Boosting Systems

On low buildings or where the water tank is not high above the point of use some systems install a water pressure booster pump and tank. A water pump (WATER PUMPS, TANKS, DIAGNOSTICS) and probably a water pressure tank (WATER TANK BLADDERS & CAPTIVE AIR) will certainly be needed for ground-level or below-ground-level water storage cisterns.

Photograph of a water pressure booster pump and tank system

Water pressure booster pumps and tanks may be installed in buildings where municipal water is supplied, located on rooftops or anywhere in a building, so don't assume that just because you see a pump and tank that the building is served by a private well.

Water pressure boosting systems using a water pump and water tank are also installed in homes where the municipal water supply pressure is low.

See WATER PRESSURE LOSS DIAGNOSIS & REPAIR for details on how to correct low water pressure in a building.

We discuss water pressure booster pump and tank systems in detail

Readers of this document should also see WATER PUMP REPAIR GUIDE an specific case which offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost and
see Wells, Cisterns, & Springs for a discussion of types of drinking water sources and what goes wrong with water supplies.

If you're looking for information on types of septic tanks see
our SEPTIC SYSTEM DESIGN SPECIFICATIONS which includes articles about various types of septic tanks, steel, concrete, plastic, etc. The illustration at page top is courtesy of Carson Dunlop, Inc. in Toronto.


Continue reading at CHECK VALVES, WATER SUPPLY or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



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