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How to Diagnose & Repair Clogged Hot Water Piping or a Clogged Tankless Coil HeatAPedia © Enter your search terms Submit search form   Search This Website - InspectAPedia.com

• 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 correct clogging at the tankless coil in order to improve the hot water pressure, quantity, flow from a tankless coil used for making domestic hot water. We include a simple diagnostic procedure to find out if your bad hot water pressure is due to clogging in the hot water piping or in the tankless coil itself. If you need to improve the hot water temperature and flow from a tankless coil system that is not clogged, see Tankless Coil for Hot Water Increase. 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 2008 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 Check for and Correct Clogged Piping or Clogged Tankless Coil to Improve Hot Water Pressure or Flow

Abandoning a tankless coil altogether: When we bought our house the tankless coil was almost totally clogged with minerals, and we figured that it wouldn't provide enough hot water anyway, so we abandoned it. In the photo at left you can see the round black tankless coil face, with two holes - where we removed the cold-water-in and hot-water-out pipes and simply abandoned the tankless coil.

A separate water heater was installed in our utility area. (We'd have preferred an indirect-fired water heater which is discussed later in this article but that's not what we got.)

Guide to Acid Flushing of Clogged Tankless Coils or Clogged Hot Water Piping

Some plumbers will attempt to clean out water supply piping that has become mineral-clogged. The general procedure is the following:

1. First, confirm the diagnosis that the problem is clogged piping, not a clogged strainer, valve, or improper pipe connections (such as use of too much solder on copper piping connections). Some types of pipe or tankless coil clogging such as due to sediment, rust, or mechanical damage will not be corrected by an acid flush. See WATER PRESSURE LOSS DIAGNOSIS GUIDE and Water pipe clog repair guide for more general water pressure diagnosis guidance.
2. Install shutoff valves and drain valves at each end of the water supply piping (or right at the tankless coil inlet and outlet piping)
3. Shut off water supply to and then drain the piping or tankless coil to be cleaned
4. Connect the two drain fittings (at the two ends of the copper piping or tankless coil) to hoses (often washing machine hoses are used) as follows:
   1. One drain hose empties into a bucket
   2. The other drain hose is connected to a "pony pump" capable of pumping acids
5. Prepare the acid flush mix: The bucket receives a few gallons of a cleaning acid selected by the plumber (such as muriatic or dilute sulfuric acid)
   CAUTION: Acids can cause dangerous burns or loss of vision: appropriate hand, eye, and skin protection are needed as well as protection against acid spills.
6. The acid is pumped cycling through the piping or tankless coil to be cleaned.
7. The acid is flushed from the piping or tankless coil using fresh water
8. The hoses and acid are removed and the drain valves closed.
9. The plumbing water supply to the cleaned section of piping or tankless coil is turned back on
10. The plumbing system is flushed to be sure no acid remains in the piping

Does acid flushing of water piping or tankless coils work?

Often an acid flush will indeed restore or improve water pressure and flow through previously-clogged building piping. But the process has these limitations:

1. Etching speeds new clogging: Some plumbers have told us that the acid flush process also leaves the piping interior "etched" - this roughened surface may result in mineral-clogging recurring sooner than it did in the first place.
2. Acids can cause leaks in previously marginal piping that is already thin and corroded
3. Acids may leak out and cause damage if piping is not in good condition
4. Clogging will recur: If the cause of the original pipe clogging is not corrected, it will recur. For example, hard water that results in mineral clogging of pipes or clogging of a tankless coil can and should be treated with a water softener. (A water softener won't remove clogging in pipes but it will help prevent its occurrence or recurrence). See WATER SOFTENERS The pile of tankless coils shown at the top of this page is probably an example of terrible recurrent mineral clogging of tankless coils at the building where we took this photo.
5. Working with acid is dangerous. Some plumbers will therefore not provide this service.

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.

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
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 (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.
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.

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
• 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 indired-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.

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
ALTERNATIVE HOT WATER SOURCES
  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
ANTI SCALD VALVES
CHIMNEY INSPECTION DIAGNOSIS REPAIR
Clogged Piping & Hot Water Flow
ELECTRIC WATER HEATERS
GAS FIRED WATER HEATERS
  DRAFT HOODS - gas fired
  Gas BTUH & Cubic Feet
  GAS PIPING, VALVES, CONTROLS
  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
SEWER GAS ODORS
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
More Information

Technical Reviewers & References

Particular thanks are due to experts and also consumers who read these articles and suggest corrections, changes, and additions to the material. Content suggestions, technical corrections and content critique are invited for any of the content at our website.

• Daniel Friedman - InspectAPedia.com ^TM Website Author/Editor
• 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
• Critique, contributions wanted: Contact Us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

Use links 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.

More expert information on this topic

More Information on Inspecting and Repairing Heating Systems

• 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.)

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