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AGE of WATER HEATERS
ALTERNATIVE HOT WATER SOURCES
ANODES & DIP TUBES on WATER HEATERS
ANTI SCALD VALVES
APPLIANCE DIAGNOSIS & REPAIR
APPLIANCE EFFICIENCY RATINGS
AQUASTAT CONTROL Functions
BACKDRAFTING HEATING EQUIPMENT
BACKFLOW PREVENTER, HEATER WATER FEEDER
CARBON MONOXIDE - CO
CHECK VALVES, WATER SUPPLY
CLOGGED SUPPLY PIPING
CROSS CONNECTIONS, PLUMBING
DEBRIS in WATER SUPPLY, Water Heater
DRAIN a WATER HEATER TANK
ELECTRIC WATER HEATERS
FLOODED WATER HEATER REPAIR
FREEZE-PROOF A BUILDING
GALVANIC SCALE & METAL CORROSION
GAS BURNER FLAME & NOISE DEFECTS
GAS FIRED WATER HEATERS
GAS PIPING, VALVES, CONTROLS
HEATING COST SAVINGS METHODS
HOT WATER EXPANSION TANKS
HOT WATER SUPPLY
HOT WATER IMPROVEMENTS
HOT WATER DELIVERY SPEED UP
HOT WATER EFFICIENCY IMPROVEMENT
HOT WATER PRESSURE EXPANSION RATE
HOT WATER PRESSURE IMPROVEMENT
HOT WATER PRESSURE LOSS
HOT WATER PROBLEM DIAGNOSIS
HOT WATER QUANTITY IMPROVEMENT
HYDROGEN SULFIDE GAS
INDIRECT FIRED WATER HEATERS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
NO HEAT - NO HOT WATER: HEATER DIAGNOSIS
NOISE, WATER HEATER
ODORS IN WATER
PIPING IN buildings, Clogs Leaks Types
RELIEF VALVE LEAKS
RELIEF VALVE, WATER HEATER
SCALE REMOVAL, WATER HEATERS
SEWER GAS ODORS
SOLAR HOT WATER HEATERS
TANKLESS WATER HEATERS
THERMAL EXPANSION of HOT WATER
THERMOSTATS, WATER HEATER
TIMERS for ELECTRIC WATER HEATERS
WATER HEATER ALTERNATIVES
WATER HEATER ANODES, DIP TUBES
WATER HEATER AIR INLET
WATER HEATER DEBRIS FLUSH
WATER HEATER DRAIN PROCEDURE
WATER HEATER EFFICIENCY
WATER HEATER FLUSH PROCEDURE
WATER HEATER NOISE DIAGNOSIS, CURE
WATER HEATER PROBLEM DIAGNOSIS
WATER HEATER COMPARISONS, PROPERTIES
WATER HEATER SCALE
WATER HEATER SAFETY
WATER HEATERS for HOME HEATING USE?
WATER ODORS, CAUSE CURE
WATER PIPES, Clogs Leaks Types
WATER PRESSURE TOO HIGH: DANGERS
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER QUANTITY IMPROVEMENT
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING
Clogged tankless coils:
Here we explain 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.
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How to Check for and Correct Clogged Piping at a Hot Water Heater Tank or Clogged Tankless Coil to Improve Hot Water Pressure or Flow
Corrosion, debris, dip tube or anode problems in the water tank:
Accumulated debris in a water heater, and debris from a corroded or disintegrating hot water tank dip tube or hot water tank sacrificial anode can also block the hot water outlet opening, resulting in low hot water pressure in a building.
[Click to enlarge any image]
Clogged hot water supply piping:
Water supply pipes may be clogged at the water heater or at other locations, from minerals, soil, or other debris.
and WATER HEATER SCALE DE-LIMING PROCEDURE for diagnosis and repair procedures.
Tankless Coil Clogging Diagnosis & Repair - Removing Lime & Scale from a Tankless Coil Water Heater - also for Side-Arm Coils
Hot water pressure and hot water flow in a building may be poor even where a mixing valve has been installed. This condition could be due to poor overall building water pressure or due to clogged pipes.
If cold water pressure is good and hot water pressure is poor, the problem is not an overall building water pressure issue. There is a problem with the hot water system that needs to be found and corrected.
If hot water pressure is strong when the water is first turned on but flow quickly falls off to a weak hot water stream, it's likely that the hot water piping (or tankless coil) are clogged.
Often this repair involves using acid to try to remove minerals that are clogging hot water system piping or a tankless coil, or the tankless coil may need replacement.
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
Photo at left: lime scale fragments collected from a water heater. Similar hard limescale forms inside of hot water pipes and particularly in tankless coils used to produce domestic hot water. [Click to enlarge any image]
The general procedure is the following:
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:
Krappe described using an acid-resistant pump and tubing connected to fittings to circulate an acid-wash through scale-clogged copper piping back in 1940. Plumbers still use this method today. The apparatus must be designed to let the scale particles and gases escape. Plumbers may simply use an acid-proof pony pump and fittings to cycle the acid wash using a plastic bucket as the receiving sump.
Watch out: this is a dangerous procedure risking acid burns or other hazards. Don't try this procedure if you are not trained and equipped to do so.
But we have been informed by some plumbers that using acids to clean a tankless coil leave the coil internal surfaces etched and that the result can be faster scale formation than previously
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 for a discussion of loss of water pressure due to clogged piping or clogged tankless coils.
At LARGER DIAMETER WATER SUPPLY PIPES 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 Prevent Tankless Coil Clogging Again in the Future?
Field Report: Two Extra Steps to Improve the Effectiveness of Tankless Coil De-Liming Procedure
Your information on how to remove scale in a tankless coil to improve hot water pressure and flow led to me doing this task myself. I am very mechanically inclined and rather technologically proficient but I still wanted to get an understanding of the processes.
I had a pump that would do the job but I was concerned about using an acid, even diluted.
I turned off the valves separating the tankless coil in my Burnham oil burner and luckily had tees in place already. All I had to do was get fittings for the garden hose adapters and screw them in place, I then connected the hoses to the pump and one to drain freely into my 5 gallon pail filled with about 2 gallons of water.
I then added a 28 ounce container of Lime-A-Way and started pumping. The water was nearly non-existent when I started and the pumps thermal overload went off giving me a break.
I did this pump on-thermal off routine about three times, each time letting the solution sit in the tankless coils for approximately a half hour. I was getting almost no improvement. I then decided to reverse the flow thinking what could be the harm. The pump started and the bursts of gray water were getting more and more frequent. After three more thermal overloads I was running freely. Success is at hand!
But wait! All this bragging of success has its downside. As best as I can remember this issue isn't covered anywhere on your site.
Flush Debris from Faucet Strainers & Valves after De-Liming Water Pipes or a Tankless Coil
What I found is that after the water flow had returned to normal I still had low flow after a few bursts in my faucets upstairs. I then removed the aerators and strainers from the faucets and all flow had finally returned!
It might be a good idea to add a step to your water pipe or tankless coil de-liming or de-scaling process to remove the strainers and aerators from their faucets before turning them all on to rinse the tankless coil and system.
and WATER PIPE CLOG REPAIR for details about diagnosing and clearing clogs in pipes, faucet strainers, and plumbing valves, including debris flushing - Ed.]
Bernie Daraz, Newtown, CT
Watch out: using Lime-A-Way, EasyPaks®, or Jelmar CLR® ("stain removing" cleaners designed to remove rust, calcium or lime) and similar cleaners to remove the white mineral crust on exposed metal surfaces such as a stainless steel kitchen sink can leave a black stain that is difficult to remove. If you already have this problem, try using a nonabrasive cleaner designed for cleaning stainless steel surfaces, such as ScotchBrite™.
As we discussed beginning in the previous section of this article, there are several different hot water problems:
The articles listed below offer more details about steps one can take to increase hot water quantity, pressure, and flow in a building.
The topics discussed in this article address improving hot water flow and improving hot water total quantity.
The following articles discuss alternative ways to produce domestic hot water for washing and bathing.
Ways to improve total hot water quantity, pressure, temperature and flow are discussed beginning at HOT WATER IMPROVEMENTS
Thanks to Carson Dunlop, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article.
For an explanation of the role of boiler temperature in the rapid formation of lime and scale clogging in tankless coils used for domestic hot water production, see WATER HEATER SCALE PREVENTION
Continue reading at TANKLESS WATER HEATER INSTALLATION REQUIREMENTS, COSTS or select a topic from the More Reading links shown below.
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Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
Question: time to use an acid wash in my tankless coil?
(Apr 29, 2014) john popa said:
An acid wash has other risks including toxicity - not something to undertake lightly.
And tankless coil tubing is copper, not likely to be a source of red rusty water.
As long as you are not seeing the same discoloration elsewhere, the unused pipe theory holds water.
I took this photo of reddish brown water running into a bath tub
under just the same conditions as you describe.
There may be other implications: galvanized pipes in an older home mean new piping is in your future.
Question: no hot water from our geyser
(June 6, 2014) Anonymous said:
. Can you assist with a solution
Are you seeing no water flow at all or water flows but is not at all hot?
If the former look for a debris-clogged valve or pipe elbow and try flushing the piping system
If the latter the problem is with the geyser itself not the water stoppage
(Aug 15, 2014) D. Laws. Near Bedford, Beds. said:
You're correct that scale or lime will tpically remain in and on the bottom of the hot water cylinder. We've removed such scale by removing the heater's bottom drain, draining out all of the water, and then GENTLY probing and breaking up loose scale into fragments that would flow out through the drain opening. We then flushed the heater by briefly sending bursts of cold water in at the heater inlet.
If scale is absolutely solid on a hot water cylinder interior surface, only by using a de-scaling agent are we likely to get that out. If you use chemicals you'll want to be sure the cylinder is very thoroughly flushed to avoid drinking or bathing in something harmful.
Once cleaning the cylinder, (for U.S. & Canadian readers - a hot water tank) the most effective long term fix for hard water high in mineral content is to install a water softener. You may hesitate at that expense, but consider that a longer-lasting solution is likely to be less costly and less disruptive than ruining the building piping and heater with scale.
5 Feb 2015 Robin said:
In reference to my question below, the house is only about 8-9 years old and went unoccupied for 2 of those years.
I would first have the water tested for hardness and for aggressiveness or corrosivity. Based on those results you may want to install a water treatment system to process all of your home's incoming water to avoid these problems.
An alternative worth considering is to abandon the tankless coil approach to making hot water completely by installing a separate water heater. An option to consider is the installation of an indirect-fired water heater. See
Questions & answers or comments about how to un-block or de-clog a tankless coil used for making hot water.
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