Guide to Hot Water Tank Insulation Safety InspectAPedia® -
Water Heater Insulation: How to Insulate A Hot Water Heater Tank - Should You Insulate the Water Heater?
Does insulating a water heater make it unsafe? Do not cover up pressure/temperature safety relief valves with water heater insulation
Guide to adding insulation to hot water water heater tanks
Water tank insulation safety warnings from water heater manufacturers
Is insulating the water heater tank worth it?
What is the energy savings from insulating a hot water tank?
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This article discusses when and how water heater tanks may be insulated, gives important water heater insulation safety warnings, and discusses whether you should insulate your water heater at all. This discussion is part of a series of articles on how to improve the hot water pressure, quantity, flow, and water temperature safety in a building.
Should You Add Insulation to the Water Heater Tank?
Most new water heater tanks come with factory-installed insulation.
If your water heater tank was purchased in the last decade it may be a model that is already adequately insulated.
In fact some water heater manufacturers recommend against adding external water heater insulating blankets to their equipment, or indicate that their equipment does not need extra insulation.. (Arlene Puentes).
Still, some owners want to reduce standby heat losses from their water heater by adding an insulating blanket sold for that purpose. Below we provide important safety advice for people planning to add water heater insulation, and we offer a concluding opinion about the value of adding insulation to a modern water heater tank.
Water Heater Insulation Safety Advice
If your water tank is old, poorly insulated or if your water heater is not insulated at all, your plumbing supplier or building supply store can provide a water heater insulating blanket kit. See Range Boiler Water Heaters for an example of heaters that were commonly left completely uninsulated (when heating oil and gas were cheap). It can make sense to add insulation to such devices.
SAFETY WARNING:Do not add water heater insulation without reviewing both the safety warnings we list below and also any safety warnings issued by the manufacturer of your own water heater brand and model. Failure to follow safe procedures when insulating a water heater could result in a fire or explosion.
In our photos at page top and just above, the water heater blanket has been poorly installed. Above the insulation has been installed on an electric water heater, the relief valve is improperly installed, and other details about this particular insulating blanket installation suggest that it has not been installed following the recommendations of the water heater manufacturer. In the photo you can see that this valve is missing its discharge tube as well - an unsafe condition.
The warnings we issue below were suggested by Arlene Puentes and are based on a review of water heater instruction manuals from Rheem and AO Smith, two prominent manufacturers of residential water heaters.
Is extra water heater insulation permitted and safe? If adding insulation to a water heater, first make sure that external insulation is permitted for your model and brand of water heater, then be sure it's installed safely. If in doubt, check with the manufacturer of your water heater before adding insulation - most water heaters will include a label which has a toll-free telephone number for this purpose.
Don't let insulation cover or block operation of a temperature/pressure relief valve: The water tank insulating blanket should be cut to permit the relief valve and its discharge tube to remain visible and unobstructed so that it can open in an emergency and so that we can see if it is leaking (which means there is a safety concern)
Flue gas safety: Don't let water heater insulation cover or block the flue gas vent draft hood on gas fired water heaters or you may prevent proper venting and the system may be unsafe, risking carbon monoxide hazards. AO Smith, a gas water heater manufacturer advises that you should not put insulation over any part of the top of the water heater.
Gas valve safety: do not let water heater insulation cover any part of the gas valve or controls
Fire safety: Don't place insulation where it can be damaged or set on fire by exhaust flues or oil or gas burners
Gas burner or Oil burner safety: don't place insulation on a water heater where it could block combustion air that the gas or oil burner need or the system may be unsafe. Keep water heater tank insulation at least 8" from the floor on gas-fired water heaters to be sure that there will be adequate combustion air for the gas burner. Otherwise your water heater may produce deadly carbon monoxide gas.
Do not cover the access cover or door that opens for inspection or service of the gas burner.
Preserve all of the labels, instructions, safety warnings, etc. that are affixed to the water heater. This means that you should either not cover them with insulation, or you should obtain new stick-on labels from the manufacturer, and install them on the outside of the new insulating blanket.
Concluding Opinions about Adding Insulation to a Residential Water Heater
Regrettably, by the time we respect all of these "don't cover" this or that warnings from the water heater manufacturers, it becomes apparent that adding water heater insulation on a modern already-insulated unit is probably more trouble and risk than it's worth.
You may be able to skip adding water heater insulation and you may be able to save more on water heating cost if you simply use some of our other recommendations such as turning down hot water temperature, using less total hot water volume, or using staging tanks to "pre heat" incoming water to the water tank from ambient building heat.
And doing anything to your water heater that does not follow the manufacturer's recommendations may be both unsafe and a cause for voiding the warranty:
"The manufacturer’s warranty does not cover any damage or defect caused by installation, attachment or use of any type of energy saving or other
unapproved devices (other than those authorized by the manufacturer) into, onto or in conjunction with the water heater. The use of unauthorized energy saving devices may shorten the life of the water heater and may endanger life and property. The manufacturer disclaims any responsibility for such loss or injury resulting from the use of such unauthorized devices " -- Rheem.
How do we Improve the Hot Water Volume & Quantity?
As we discussed beginning in the previous section of this article, there are several different hot water problems:
Poor hot water flow, or bad hot water pressure, which is usually a piping or clogging problem or an overall building water pressure problem
Poor hot water quantity: not enough hot water, or running out of hot water very quickly. Insufficient hot water quantity may be due to the way hot water is being made (a water heater that is too small, a tankless coil on a new small heating boiler, or an instantaneous water heater that is being asked to supply hot water too rapidly)
Hot water temperature that is not hot enough: water temperature is just too cool. Insufficient hot water temperature may be due simply to the setting of a temperature control on a water heater or mixing valve, or it may be due to flowing water too fast through a tankless coil. Hot water that is not hot enough can be caused by quite a list of problems, some of which are easy to correct. See Temperature of Hot Water is Too Low for steps to correct water that just won't get hot.
Previously we explained how a tankless coil makes domestic hot water, how to get more hot water from a tankless coil, how to avoid scalding, and how to detect clogged hot water piping.
Below we discuss other steps that can be taken to improve hot water quantity. And having a greater quantity of hot water also opens the way to taking steps to improve hot water pressure. (If we increase hot water pressure but lack adequate hot water quantity the result is we run out of hot water faster than ever.)
Articles Describing Steps to Increase Hot Water Quantity
The articles listed below offer more details about steps one can take to increase hot water quantity, pressure, and flow in a building. Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Extra Tanks to Increase Hot Water- pre-heat your hot water absorbing ambient building heat or increase hot water quantity with cascaded, staged, multiple water heaters, possibly using more than one energy source
Active water pre-heating tank: install a water heater (oil, gas, solar, electric) on the water piping upstream, that is, before water enters the tankless coil (or primary water heating tank, whatever water heating method is used).
This water tank can be left off when there is not much demand for hot water, in which case it will function as a passive water pre-warming tank as we discussed above. When a greater quantity of hot water is going to be needed (say many weekend visitors to a building), turn on the water heater to permit it to "boost" hot water headed for the tankless coil.
As occupants in the building draw hot water out of the system, heat will be drawn from the heating boiler and tankless coil at a very low rate, possibly not at all, until we've exhausted the hot water that was stored in the separate water heater tank.
Some people install this system backwards: hot water is fed from the tankless coil into a water heater tank. This is a much less efficient way to make hot water as all of the water entering the water heater tank will always cause the heating boiler to run. We do not recommend this arrangement.
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Arlene Puentes, an ASHI member and a licensed home inspector in Kingston, NY, and has served on ASHI national committees as well as HVASHI Chapter President. Ms. Puentes can be contacted at ap@octoberhome.com
AO Smith produces AO Smith water heaters in addition to Reliance, State, Maytag and others.
www.aosmith.com/prod/wpc.htm. AOS's gas water heater manuals offering advice and safety warnings about adding water heater insulation are available at
www.statewaterheaters.com/lit/im/res-Elec/184671-000.pdf and at
www.hotwater.com/lit/im/res_gas/184123-000.pdf
Rheem who also makes electric water heaters provides a manual for electric water heaters at
waterheating.rheem.com/content/resources/documents/use_care/ResElecProfessional.pdf. Rheem says, as do other water heater producers, that their water heaters
meet the "National Appliance Energy Conservation Act
standards with respect to insulation and
standby loss requirements making an
insulation blanket unnecessary"
Rheem also warns consumers that adding an insulation product [or making any other modification to their equipment] is likely to void the product warranty and may be unsafe.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
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