Rooftop Water Tanks, Cisterns & Free-Standing Water Storage Towers
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 tanks, range boilers, indirect-fired water heaters
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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
Rooftop Water Tanks, Water Towers & Other Water Storage Systems
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]
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
. In New York City elevated water towers such as those shown below have been in use since the late 1800's. - The New York Times (2014).
See additional water storage tank details at CISTERNS.
Large Water Storage Tanks on Towers or Free-standing Water Tanks at Ground Level
Elevated tower-supported water storage tanks are used both to store water and to provide water at pressure to individual buildings, building sites, or entire communities, as we illustrate in the photographs below.
At left is a sketch showing a traditional water storage tank on a tower connected to and located adjacent to a water well.
Below we illustrate a horizontal cylindrical water storage tank at a damp in Dutchess County, New York in the U.S.
Water storage tank & tank tower or support construction need to confront
Covering: to protect the stored water against contamination
Overflow handling: to direct overflow to ground level
Circulation within the storage facility
Gravity loads: the dead weight of materials of the water tower & storage tank construction
Live Loads: the varying weight of water stored in the tank depending on the water level to which the tank is filled
Wind Loads: varying by terrain conditions and geographic area, water towers need to withstand loads from hurricanes, hilltop winds, confined areas creating a wind-tunnel effect. T
he design engineer or architect for a water tower will consult a data source such as the International Building Code (IBC) where the code provides wind speed data at 30 feet above ground, and will add consideration for tower height, shape, location within local terrain, weather exposure (sun, snow, wind), etc.
For example a design wind speed of 80 mph translates to a surface pressure of 18 psf (0.00256 * the speed of the wind); tower designs need to allow for the maximum anticipated wind speed at the site. In coastal areas this may mean a wind speed allowance of 150 mph.
Fire code concerns: exposure to wild fires
Enclosed non-residential towers vs. enclosed structures that may add heating requirements
Access: for inspection, water tower interior cleaning, inspection & testing, maintenance, repair: ladders, stairs, etc. as well as light & ventilation for enclosed structures.
Water Tank & Water Tower Construction Standards & References
NFPA 22: Standard for Water Tanks for Private Fire Protection
Bhardwaj, Vipin, "Reservoirs, Towers and Tanks, Drinking Water Storage Facilities", National Drinking Water Clearinghouse, West Virginia University, P.O. Box 6064, Morgantown, WV 26506-6064, retrieved 4/15/14, original source: http://www.nesc.wvu.edu/pdf/dw/publications/ontap/2009_tb/reservoirs_towers_tanks_dwfsom15.pdf
HDR Engineering, Inc. 2001.
Handbook of Public Water Systems
Edition. John Wiley and Sons, Inc.: New York, New York
Hobbs, Aubrey Thomas (ed.) 1969.
Manual of British Water
. Vol 2. W. Heffer and Sons, Ltd: Cambridge,
"Fall protection requirements for workers constructing a water tower while on a scaffold", US Department of Labor, OSHA, Standard 1926.451(g) and others, retrieved 4/15/14, original source https://www.osha.gov/pls/oshaweb/owadisp.show_document? p_table=INTERPRETATIONS&p_id=25047
Rivera, Ray, Ruynyeon, Frank G., Buettner, Russ, "Inside City's Water Tanks, Layers of Neglect", The New York Times, 27 January 2014
The New York Times, "E. Coli Found in Water Towers at NYC Buildings: Report
The city says the water towers are safe", The New York Times, 27 January 2014 - Excerpt The city told the paper that its tanks -- the more than 10,000 of them currently in use -- are all safe and that health inspection standards are up to par. Though dozens of New Yorkers have called 311 each year to complain they've gotten sick from drinking tap water, the city says none of the illnesses have been traced back to the tanks, according to the Times.
Obstruction lighting standards—Water towers, grain elevators, gas holders and similar obstructions.", Washington State Legislature, retrieved 4/15/14, original source: http://apps.leg.wa.gov/wac/default.aspx?cite=468-240-205
"Water Tower", Princeton University, www.princeton.edu, retrieved 4/15/14, original source: https://www.princeton.edu/~achaney/tmve/wiki100k/docs/Water_tower.html also cited at Wikipedia below
"Water Towers, Building Code, Design & Geologic Notes", water-towers.com, retrieved 4/15/14, original source: http://www.water-towers.com/WtrsCodeNote1.html
"Water Tower", Wikipedia, retrieved 4/15/14, original source: http://en.wikipedia.org/wiki/Water_tower
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.
Specifically, 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.
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:
UV (ultra-violet) light degrading HDPE plastics over time, making them weak, and
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
Attic Cisterns or water tanks are installed in some buildings
to perform the same function as rooftop-mounted water tanks.
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.
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
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 at PASSIVE SOLAR HOME, LOW COST.
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 at CISTERNS.
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.
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.
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
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 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.
I have a gravity water tank roof top on my house-Water is pumped up by the city when working ok-When the water (municipal) is not working I use the roof tank,
Generally what I do is shut the valve off at the street, then open the valve on the rooftop tank and it gravity feeds down into house.
The tank is located rooftop has 1 line going into the top of the tank for the inlet of water into the tank, the other lines is at the bottom that the water go's into the house..
Where would the check valve be located at? Best place to install it?
Will it interfere with the pressure if the water is only gravity with no pump?
James C. 6/27/2014
I'd put the check valve on the tank side of the shutoff controlling water coming from the street main. In that location the check valve will not be between the tank serving as the buildng water source and the fixtures and piping that the tank serves.
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Water Storage: Tanks, Cisterns, Aquifers, and Ponds for Domestic Supply, Fire and Emergency Use--Includes How to Make Ferrocement Water Tanks, Art Ludwig, Oasis Design (May 30, 2005), ISBN-10: 0964343363, ISBN-13: 978-0964343368, Quoting: A do-it-yourself guide to designing, building, and maintaining water tanks, cisterns and ponds, and sustainably managing groundwater storage. It will help you with your independent water system, fire protection, and disaster preparedness, at low cost and using principles of ecological design. Includes building instructions for several styles of ferro cement water tanks.
Thanks to aerospace engineer Herman Vogel, July 2010,
for providing an update on High Density Polyethylene HDPE storage tanks for water, chemicals, waste oils, etc.
Smart Tank, Installation Instructions, Flexcon Industries, 300 Pond St., Randolph MA 02368, www.flexconind.com, Tel: 800-527-0030 - web search 07/24/2010, original source: http://www.flexconind.com/pdf/st_install.pdf [Copy on file as /water/Smart_Tank_Flexcon.pdf ] -
Typical Shallow Well One Line Jet Pump Installation, Grove Electric, G&G Electric & Plumbing, 1900 NE 78th St., Suite 101, Vancouver WA 98665 www.grovelectric.com - web search -7/15/2010 original source: http://www.groverelectric.com/howto/38_Typical%20Jet%20Pump%20Installation.pdf, [Copy on file as /water/Jet_Pump_Grove_Elect_Jet_Pumps_1.pdf ] -
Typical Deep Well Two Line Jet Pump Installation, Grove Electric, G&G Electric & Plumbing, 1900 NE 78th St., Suite 101, Vancouver WA 98665 www.grovelectric.com - web search -7/15/2010 original source: http://www.groverelectric.com/howto/38_Typical%20Jet%20Pump%20Installation.pdf, [Copy on file as /water/Jet_Pump_Grove_Elect.pdf ] - Cooperative Extension, School of Forest Resources, web search 07/24/2010, original source: http://pubs.cas.psu.edu/FreePubs/pdfs/XH0002.pdf
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