InspectAPedia ^®

How to Get More Hot Water Pressure, Temperature, & Quantity from a Tankless Coil InspectAPedia®  -

• How to improve hot water pressure and how to improve hot water quantity from a tankless coil
• How to stop running out of hot water, How to make hot water hot enough

Here we discuss how to improve the hot water pressure, quantity, flow, and water temperature obtained from a tankless coil used for making domestic hot water. If your hot water pressure is declining because of a clogging tankless coil, be sure to see Clogged Piping / Tankless Coil & Hot Water Flow for diagnosis and repair advice. Thanks to Carson Dunlop, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article.

Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. © Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use the links at page left to navigate this document or to go to Other Website Topics. Green links at left show where you are in our document & website.

How to Increase Hot Water Quantity & Flow When a Tankless Coil is Installed - how to avoid running out of hot water

Use a flow limiter to increase the length of time that you can run the hot water and to increase hot water temperature

Tankless coils do not provide infinite hot water. Cool water entering the coil draws heat out of the boiler water and into the house water. The oil or gas burner that reheats the heating boiler cannot pump heat into the boiler as fast as the tankless coil is removing heat. That's because water is entering the coil at 40 to 55 deg F in most cases, and it's trying to leave at the boiler temperature that may be close to 200 degF.

So if you run water too fast through the tankless coil it'll draw heat out of the boiler quickly and you'll have great hot water pressure, but not for very long. Then you'll just have tepid or cold water pressure. Some tankless coils have a flow limiting valve mounted right at the coil to prevent water from flowing through the coil too fast.

Using a flow limiting valve on a tankless coil lets you run the hot water longer before you run out by forcing you to run it more slowly.

Use of a flow limiting valve, because it slows the passage of cold water through the water heater, will also permit the water to arrive at the plumbing fixture at a higher temperature - the hot water will be hotter.

Intelligent use of shower controls to restrict hot water flow can save hot water costs and provide longer shower bathing time

Even when a flow limiter is not installed in hot water piping, a bather can save on hot water heating costs by smart use of shower controls. Some bathers turn the hot water all the way to it's fastest flow position, followed by turning on lots of cold water in order to avoid being scalded. Instead of this fastest-flow best water pressure approach, turn the hot water to a less powerful stream, which will require also turning on less cold water to obtain a comfortable shower temperature.

This method of bathing does not really provide a greater quantity of hot water in a building, but by drawing hot water out of the water heater more slowly, one can either have longer time in the shower, or subsequent bathers can have adequate hot water at less total water heating cost.

Use an anti-scald valve to increase hot water quantity and protect from hot water burns

Therefore we can expect to draw a larger quantity of (tempered) hot water from the tankless coil on such a system than otherwise. We will have more total domestic hot water for washing and bathing, and we have safer hot water (non-scalding) than if we omitted this pair of controls.

See Mixing Valves for a detailed discussion of how to install, set, and use mixing valves, anti-scald valves, or tempering valves on water heating systems to avoid scalding burns and to improve hot water heater performance.

Make Sure That the Tankless Coil is Not Mineral-Clogged

For details on how to diagnose a clogged tankless coil and how to repair it, see Clogged Piping / Tankless Coil & Hot Water Flow.

See Tankless Coils for an explanation of how these water heaters work and why they clog up and how to stop clogging up the coil.

See Water pipe clog repair guide for a discussion of loss of water pressure due to clogged piping or clogged tankless coils.

At Larger Diameter Water Supply Piping we discuss the benefits of using larger diameter water supply piping both to improve water pressure and flow and also to delay the clogging of pipes due to minerals or rust.

See WATER SOFTENERS for a discussion of how to use a water softener to prevent hot water pipe clogging and tankless coil clogging (and reduced hot water pressure and flow). A water softener can prevent mineral-clogging of pipes or the tankless coil but regrettably, installing a water softener after your pipes or tankless coil are already clogged will not fix that problem.

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:

1. Poor hot water flow, or bad hot water pressure, which is usually a piping or clogging problem or an overall building water pressure problem (Clogged Piping / Tankless Coil & Hot Water Flow) In this case the water is hot enough and we may seem to have plenty of hot water, but the flow, or pressure of hot water in the building is too weak and (a good diagnostic) the hot water pressure is noticeably less than the cold water pressure in the building.
2. 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, such as a water heater that is too small (perhaps 30 gallons for a large family), a tankless coil on a new small heating boiler, or an instantaneous water heater that is being asked to supply hot water too rapidly.
3. 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.
4. Slow hot water supply recovery time: we have water that is hot enough, and we have plenty of it (or maybe not), but when we run out it takes too long for the hot water system to "recover", that is, to again deliver hot water after previously running out. The speed with which a water heater re-heats cold water which has entered its tank depends mostly on the type of heater and on its overall size in gallons. Here are some examples:
   1. Oil-fired hot water heaters warm-up faster than gas or electric water heaters
   2. Gas-fired water heaters warm up incoming water faster than most electric water heaters
   3. A 50-gallon hot water heater tank that has been cooled down to a low temperature will take longer to re-heat than a 30-gallong hot water tank of the same type (oil, gas, electric, solar).

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.

• Anti-Scald Valves & Hot Water Quantity - improve safety and meter hot water more slowly - makes it last longer
• CLOGGED PIPING & Hot Water Flow - diagnose and correct poor hot water pressure and flow due to pipe clogging. See WATER SOFTENERS for a discussion of how to install and adjust water heaters to prevent hot water piping clogging or tankless coil clogging due to hard water.
• 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
• High Efficiency Water Heaters - if replacing a water heater, consider a model that saves money in operating cost
• Insulate Hot Water Piping - worth doing where piping is accessible, especially on piping running through cool areas
• Insulate Hot Water Tank? - probably not worth doing except in special cases; important safety warnings
• Larger Diameter Water Supply Piping - worth doing if replacing clogged pipes or building new construction
• Tankless Coil Hot Water Increase - various tricks can significantly improve the safety and water quantity available
• Temperature of Hot Water is Too Low - where to look for problems when the "hot water" is not hot enough

The topics discussed in this article address improving hot water flow and improving hot water total quantity.

A Comparison of Alternative Hot Water Heaters & Sources

The following articles discuss alternative ways to produce domestic hot water for washing and bathing.

• High Efficiency Water Heaters such as direct-vent gas-fired water heaters
• Indirect-fired Water Heaters which use a separate heating boiler to produce a larger quantity of hot water
• Instantaneous Water Heaters point of use systems that have little or no standby energy losses
• Multiple water heaters in parallel to increase total hot water quantity
• Multiple water heaters in series to stage hot water heating for varying levels of demand
• Range Boiler Water Heaters an older form of indirect-fired hot water heating used with separate heating boilers
• Side Arm Coil Water Heaters similar to instantaneous and tankless coil water heaters, often used with range boilers
• Solar Water Heaters using solar collectors, an indoor water tank, pump and controls, using minimal "on-grid" energy
• Tankless Coil Hot Water Increase a heat exchanging coil immersed inside of a heating boiler heats provides (somewhat limited) hot water. various tricks can significantly improve the safety and water quantity available

The characteristics of various water heaters such as life expectancy, cost, safety, and capacity are discussed at WATER HEATER PROPERTIES

Ways to improve total hot water quantity, pressure, temperature and flow are discussed beginning at HOT WATER IMPROVEMENTS and continuing at HOT WATER QUANTITY IMPROVEMENT.

Share this Article      

...

Technical Reviewers & References

Search InspectAPedia

• Daniel Friedman - principal author/editor of the InspectAPedia^® Website
• InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
• 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.

WATER HEATERS
AGE of WATER HEATERS
ALTERNATIVE HOT WATER SOURCES
  Electric Shower Heaters
  High Efficiency Water Heaters
  Indirect-fired Water Heaters
  Instantaneous Water Heaters
  Multiple water heaters in parallel
  Multiple water heaters in series
  Range Boiler Water Heaters
  Side Arm Coil Water Heaters
  Solar Water Heaters
  Tankless Coil for Hot Water
HEATING SYSTEMS
AIRBOUND HEAT SYSTEM REPAIRS
ANODES & DIP TUBES on WATER HEATERS
ANTI SCALD VALVES
CHIMNEY INSPECTION DIAGNOSIS REPAIR
CLOGGED PIPING & Hot Water Flow
DRAIN a WATER HEATER TANK
ELECTRIC WATER HEATERS
GAS FIRED WATER HEATERS
  DRAFT HOODS - gas fired
  Gas BTUH & Cubic Feet
  Gas Conversion LP Natural Gas
  GAS PIPING, VALVES, CONTROLS
  SOOT on OIL FIRED HEATING EQUIPMENT
SPILL SWITCHES - Flue Gas Detection
HOT WATER IMPROVEMENTS
HOT WATER QUANTITY IMPROVEMENT
  Alternative Hot Water Sources & Methods
  Anti-Scald Valves & Hot Water Quantity
  CLOGGED PIPING & Hot Water Flow
  Extra Tanks to Increase Hot Water
  Insulate Hot Water Piping
  Insulate Hot Water Tank?
  Larger Diameter Water Supply Piping
  Tankless Coil Hot Water Increase
  Temperature of Hot Water is Too Low
INDIRECT FIRED WATER HEATERS
ODORS IN WATER
OIL FIRED WATER HEATERS
  DRAFT REGULATORS - barometric dampers
  OIL BURNERS
  OIL BURNER NOISE SMOKE ODORS
  OIL PIPING
  OIL TANKS
MIXING VALVES
RANGE BOILERS
RELIEF VALVES - TP Valves on Boilers
Relief Valves - Water Heaters
SEWER GAS ODORS
SEWER LINE REPLACEMENT
SOLAR HOT WATER HEATERS
TANKLESS COILS
  Clogged Piping / Tankless Coil & Hot Water Flow
  Mixing Valves
  Tankless Coil Leaks
  Tankless Coil Hot Water Increase
WATER HEATER PROPERTIES
  Electric, Gas, Oil Water Heater Efficiency
  Water Heater Life Expectancy Comparisons
  Water Heater Operating Cost Comparisons
  Water Heater Purchase & Maintenance Costs
  Water Heater Water Quantity Comparisons
  Water Heater Recovery Speed Comparisons
  Water Heater Safety Comparisons
WATER SOFTENERS

• 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

More Information on Building Diagnostic Inspections and Repairs

• Carbon Dioxide Gas Toxicity
• Carbon Monoxide Gas Toxicity, exposure limits, poisoning symptoms, and inspecting buildings for CO hazards
• Dust from HVAC? An Investigation of Indoor Dust Debris Blamed on a Heating/Cooling System Reveals Carpet Dust
• Goodman Furnace High Temperature Plastic Vent HTPV safety recall US CPSC notice
• Home Heating System Should Be Checked [for proper venting and for CO Carbon Monoxide Hazards - DJF]
• Inspection Procedures for Oil-Fired Heating Systems Detailed step by step approaches for inspecting complex systems]
• Lennox Pulse Furnace Safety Inspection/Warranty Program: Carbon Monoxide Warning
• Oil Tanks - The Oil Storage Tank Information Website: Buried or Above Ground Oil Tank Inspection, Testing, Cleanup, Abandonment of Oil Tanks
• Oil Tanks Above Ground, UL Standards, guidance for home owners, buyers, and inspectors
• Plastic Heating Vent Pipe & Other Heating Safety Recall Notices
• Weil McLain Model GV Gas Boiler/gas valve CPSC recall/repair
• 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 Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
• "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.)

InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest.

The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems

Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab

Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.

Building Inspection, Problem Diagnosis, Forensic Investigation & Testing, Repair Consulting

Contact Daniel Friedman for website content suggestions or for fee-paid consulting