Water heater insulation, a bad job (C) Daniel FriedmanGuide to Hot Water Tank Insulation Safety

  • INSULATE HOT WATER TANK? - CONTENTS: How to Insulate A Hot Water Heater Tank - Should You Insulate the Water Heater? Watch out: insulating a water heater may 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?
  • POST a QUESTION or READ FAQs about how to insulate a hot water tank (or safety and warranty reasons not to insulate the water heater)
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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.

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Should You Add Insulation to the Water Heater Tank?

water heater insulating blanket

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).

Quoting from A.O. Smith's "Gas Water Heater's Owner's Manual"

Insulation blankets available to the general public for external use on gas water heaters are not necessary with A.O. Smith products. The purpose of an insulation blanket is to reduce the standby heat loss encountered with storage tank heaters. Your A.O. Smith water heater meets and exceeds the National Appliance Energy Conservation Act standards with respect to insulation and standby loss requirements, making an insulation blanket unnecessary. - A.O. Smith Water Products Co., see REFERENCES

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 HEATER 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, or as A.O. Smith puts it,

Failure to follow these instructions can restrict the air flow required for proper combustion, potentially resulting in fire, asphyxiation, serious personal injury or death.  - A.O. Smith Water Products Co., see REFERENCES

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. - Rheem & A.O. Smith Water Products Co., see REFERENCES

Also see our advice and safety warnings about water piping insulation at Insulate Hot Water Piping.

Concluding Opinions about Adding Insulation to a Residential Water Heater

Schematic of hot water tank insulation (C) Daniel Friedman

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.




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