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 How to fix a hot water heater: diagnostic & repair procedures
- Hot Water Troubleshooting Diagnostic Guide - Basic Questions. Start troubleshooting a hot water heating system here.
- Also see articles on your specific type of water heater in Related Topics below, and see
- Questions & Answers about how the proper starting point when we need to identify & diagnose problems with building hot water tanks, heaters, piping, pressure, flow, quantity, temperature, safety, noises, or other hot water troubles.
- References
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How to fix a water heater that is not working at all or is not working adequately. This article describes the starting point for fixing problems with a building hot water supply. We pose a few questions to make sure you are taking the quickest and most economical approach to understanding, diagnosing, and fixing hot water system complaints like loss of all hot water, poor hot water flow or pressure, hot water that is not hot enough, running out of hot water, or hot water heater operating cost, noises, leaks, or maintenance.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Hot Water Troubleshooting Diagnostic Guide - Basic Questions
 Not enough hot water, depending on whom you speak with, might be that you run out of hot water too soon, or that the flow rate at the shower is too weak, or that the hot water is really not hot enough.
To really improve domestic hot water supply it's worth taking a minute to accurately describe exactly what the problem is. You won't be spending time and money on the right repair if you fix the wrong problem. Below we clear up some confusing ways people use terms.
Before we detail steps to improve building hot water supply volume, flow rate, temperature, or to fix "not enough hot water" complaints, to look at the hotwater supply troubleshooting articles below. Keep in mind that at your building you may have more than one of these conditions.
- No hot water: If you have no hot water at all, but cold water comes out of the hot water faucets, make sure that your water heater has fuel (oil or gas) or power (electric, solar). Also check for a defective high temperature limit switch (there is a reset switch on the thermostat) or for a defective upper thermostat (you'll have tepid hot water but no HOT water). See NO HEAT - NO HOT WATER: HEATER DIAGNOSIS for details about troubleshooting when you have no hot water at all.
- Hot water pressure or flow: if your problem is gradual or long-standing poor hot water pressure, or flow, that is, water comes out of the faucet or shower weakly or too slowly, start your diagnosis here at HOT WATER IMPROVEMENTS (the article below)
Poor hot water flow, or bad hot water pressure, which is usually a piping or clogging problem, mineral clogging at a water tank or tankless coil, or an overall building water pressure problem. In the article below we describe how to improve hot water pressure and flow.
If your hot water pressure has suddenly been lost but you still have some, poor hot water flow, see HOT WATER PRESSURE LOSS
- Hot water quantity: if your problem is gradual or long-standing poor hot water quantity, that is your water is hot enough, but you run out of hot water too soon. If you do not have not enough hot water quantity, you are 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. Diagnosis and repair for hot water quantity are at HOT WATER QUANTITY IMPROVEMENT.
Poor hot water quantity can also be caused by mineral deposits and clogging in a hot water tank. Mineral clogging can clog pipes (slower flow) or insulate the heat transfer (water not hot enough, slow recovery, noisy water tank). See WATER HEATER SCALE - De-Liming Procedure
- Hot water delivery time: if you want to speed the delivery of hot water to plumbing fixtures or if the recovery rate of your water heater is too slow, if the water heater is electric check for a defective upper or lower heating element. See HOT WATER DELIVERY SPEED UP for details.
- Hot water heating costs: If your hot water heating costs are too high check for:
- The hot water thermostat is set unnecessarily high - see the thermostat on the control or aquastat for your oil or gas fired water heater or tankless coil boiler; or see Electric Water Heater Thermostats
- The hot water heater tank has a sediment or scale problem - see SCALE REMOVAL, WATER HEATERS
- Check for long hot water piping runs, especially if the hot water piping is also not insulated and/or runs through cold areas, or if hot water supply piping was routed through exterior building walls (exposed to low temperatures). Running a hot water pipe right alongside the cold water supply pipe to the plumbing fixtures can also sap hot water temperature and increase water heating costs.
- Check for building occupants who waste hot water - long showers, baths, leaving the kitchen sink hot water running continuously; also check for leaky hot water faucets in the building or for wrong piping connections (we found a running toilet that had been connected to hot water instead of cold water piping)
- Check for a water heater that is too small for the building it serves - causing it to run continuously
- Check for a water heater thermostatic control that is out of calibration - keeping water hotter than its setting
- Consider making your hot water using a different, more economical method. The characteristics of various water heaters such as life expectancy, cost, safety, and capacity are discussed at WATER HEATER PROPERTIES
- Use your hot water more efficiently. See EFFICIENCY IMPROVEMENT, HOT WATER
- Hot water recovery rate: if you have good hot water, and plenty of it at a good flow rate, but when you run out it takes too long for your water heater to recover, that is usually an innate property of the water heater type and model.
The higher the BTUh input rate of your water heater the faster it will "recover". In order of recovery speed, from fastest to slowest, are tankless water heaters, oil fired water heaters, gas fired water heaters, electric water heaters. Solar water heater recovery rates vary depending on sun availability and the type of back-up hot water source provided. See ALTERNATIVE HOT WATER SOURCES.
Poor hot water recovery rate can also be caused by mineral deposits and clogging in a hot water tank. Mineral clogging can clog pipes (slower flow) or insulate the heat transfer (water not hot enough, slow recovery, noisy water tank). See WATER HEATER SCALE - De-Liming Procedure
- 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 at all or won't get hot enough.
- All water pressure is bad, at both hot and cold: If your concern with total water pressure and flow, both hot and cold, see WATER PRESSURE LOSS DIAGNOSIS & REPAIR, and if you simply run out of water, both hot and cold, see WATER QUANTITY IMPROVEMENT.
- Water heater itself is acting up or leaking: noises, smoke, odors, leaks, not working at all: you need to jump to our home page for the type of water heater you have. At each of those pages we describe the heater, its properties, and its maintenance or repair.
- ALTERNATIVE HOT WATER SOURCES, start here if your water is heated by an electric shower heaer, a high efficiency water heater, a range boiler, a side arm coil water heater, or a solar water heater
- ELECTRIC WATER HEATERS, your hot water is heated in a tank powered by electricity
- INDIRECT FIRED WATER HEATERS, your hot water is heated in a separate water tank connected to your heating boiler
- OIL FIRED WATER HEATERS, your hot water is made by an oil-fired water heater and tank. Also see OIL BURNER NOISE SMOKE ODORS
- TANKLESS COILS, your hot water is made by a coil on your heating boiler, you don't have a hot water tank
- TANKLESS WATER HEATERS or demand or point of use heaters or "instant" water heaters
- GAS FIRED WATER HEATERS, , your hot water is made by an oil-fired water heater and tank. Also see GAS BURNER Flame & Noise Defects and see GAS PIPING, VALVES, CONTROLS
Frequently Asked Questions (FAQs) about water heater troubleshooting
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
- John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
 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.
- "Solar Water Heaters", U.S. Department of Energy article on solar domestic water heaters to generate domestic hot water in buildings, explains how solar water heaters work. Solar heat for swimming pools is also discussed.
- "Heat Exchangers for Solar Water Heating Systems", U.S. DOE describes the types of solar water heater heat exchange methods between the sun and the building's hot water supply
- "Heat-Transfer Fluids for Solar Water Heating Systems", U.S. DOE, describes the types of fluids selected to transfer heat between the solar collector and the hot water in storage tanks in a building. These include air, water, water with glycol antifreeze mixtures (needed when using solar hot water systems in freezing climates), hydrocarbon oils, and refrigerants or silicones for heat transfer.
- "Solar Water Heating System Maintenance and Repair", U.S. DOE
- "Solar Water Heating System Freeze Protection", U.S. DOE,using antifreeze mixture in solar water heaters (or other freeze-resistant heat transfer fluids), as well as piping to permit draining the solar collector and piping system.
- "Scaling and Corrosion in Solar Water Heating Systems", U.S. DOE
- www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850 is the base U.S. DOE website for these article
- "Building Owner Water Heater Safety Notice", Building Department, City of Colleyville TX, web search 09/24/2010, original source: http://www.colleyville.com/dmdocuments/Building%20
Owner%20Water%20Heater%20Safety%20Notice%203-6-102.pdf
Quoting:
Water heater safety is imperative to the occupants of a building or structure. If improperly installed, water heaters can be detrimental to the structure, as well as being potentially fatal to its occupants. The proper installation of a water heater is so important that according to Texas State Law all water heater installations must be inspected by a state licensed plumbing inspector.
- "Scale formation in water heaters and methods of prevention", Krappe,
Justus Maximilian, Engineering experiment station. Gas engineering
bulletin; no. 6; Research series; no. 74; On cover: Engineering
bulletin, Purdue university. Vol. xxiv, no.
3a. June, 1940 (Layfayette Indiana) commonly referred to in some references as "Purdue University Bulletin No. 74" - thanks to researcher Robyn Goldstein for the full citation. LCCN: 40028844 & OCLC: 1038544 - Water analysis, water softening, hot-water supply. 27pages. You can obtain this document through your local library.
(full copy file at InspectAPedia 3/31/2010)
Purdue B074 can be hard to locate online.
Also Bradford White Corporation (a manufacturer of water heaters) has published excerpts from that document, available at Purdue_B074_BradfordW.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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- Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
- Carbon Monoxide Gas Toxicity, exposure limits, poisoning symptoms, and inspecting buildings for CO hazards
- 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.
- "Solar Water Heaters", U.S. Department of Energy article on solar domestic water heaters to generate domestic hot water in buildings, explains how solar water heaters work. Solar heat for swimming pools is also discussed.
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