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Guide to Rooftop Water Tanks & Cisterns
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
This article describes rooftop water tanks and cisterns, 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 also discuss using a booster pump to improve building water pressure in buildings with weak municipal water pressure or a weak rooftop
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Rooftop & Attic 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. 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 second photograph of a large rooftop water storage tank was taken in Manhattan. Rooftop storage tanks atop tall buildings have been in use for hundreds of years - this one was constructed of wood with iron bindings and is used to provide good water pressure to fixtures in the multi-story building it serves.
See details at CISTERNS.
Rooftop Water Tanks or Free-standing Water Tanks at Ground Level
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Rooftop water tanks in urban areas such as New York City may be used to supply water at high pressure to the
building below.
Water is pumped to the rooftop tank from its municipal source, then
redistributed at good pressure to the points of use in the building below.
When passing through
New York City, look at rooftops and you'll often see these tanks still in use. This sketch shows how
a rooftop tank might be constructed, though this particular sketch has the tank next to a well.
See details at CISTERNS.
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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.
see 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:
- 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.
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.
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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.
Rainwater for this cistern is collected from a near-flat rooftop 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). 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.
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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 at PUMP, WATER PRESSURE BOOSTING
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Readers of this document should also see Water pump and pressure tank repair diagnosis & cost 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 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.
Frequently Asked Questions (FAQs)
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
 Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
- Amtrol - AMTROL, Inc.,
Corporate Office,
1400 Division Road,
West Warwick, R.I. 02893
Tel: (401) 884-6300
Fax: (401) 884-4773 The company's website is at www.amtrol.com; also see Amtrol's installation and instruction manual for their Well-X-Trol water pressure control tank, a PDF file
- 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
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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