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Recirculation system

Re-circulation install/ maintenance tips
Troubleshoot recirculation pump
Cold flashes with recirculation system
Hot water recirculation system
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How water heater recirculation system works 

Part I:  Pump OFF

Hot water re-circulation system with timer turned off

Cold water available immediately, but wait for hot water.

Water- savings estimate of 15,000 gallon per year is promotional foolery: this amount equals 41 gallons per day or 2 full bathtubs of water per day.

Test your home: put empty gallon can under tub spout and see how much water is wasted waiting for hot water. Use water for plants.
Laing recirculation pump with timer at Amazon
Auto circ at Amazon
Re-circulation system
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How water heater recirculation system works

Part  II: Pump ON

Re-circulation system with timer turned on.

Hot water available, but wait for cold water.

Timer saves energy compared with recirculation system that runs full time.
Autocirc uses timer, but also turns off when temperature reaches 95, and turns on when water temperature drops to 85.


Laing recirculation pump with timer at Amazon
Auto circ at Amazon
Recirculation systems Amazon
Grundfos recirculation at Amazon
Taco recirculation at Amazon
Laing recirculation at Amazon

Recirculation in tank
See entire Auto-circ system

Water heater temperature

Can affect recirculation pump
Keep Water Heater Temperature Below 140F (60C):

High temperatures cause calcium and magnesium to come out of solution and create solids. These solids can damage pump and reduce water heater efficiency.
Can cause early water heater failure
How to adjust temp of water heater
How to maintain water heater

Water temperature inside pipe

When using thermostat operation, the pump turns ON automatically when temperature inside pipe drops below 85 degrees and then turns OFF when water temperature reaches 95 degrees F.
When using Timer, the pump runs for specified amount of time. So if water heater holds very hot water, the full tank temperature will circulate 
Grundfos circulation timer
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Grundfos installation manual
General guide for setting timer

Choose: Timer or thermostat operation?

Choose between 'Timed' operation or 'Thermostatic' operation
Use slide switch located on timer dial.

Choose timer and Program specific times: Move slide switch to timer.
Using timer, the recirculation system runs specific times of day
Timer must be reset after power outage

Or choose Thermostat operation, Move slide switch to ON.
Pump runs whenever temperature inside pipe drops below 90 degrees

To turn off the system, slide switch to OFF
General guide for setting timer


Timer or thermostat?

Timer can save money if scheduled carefully.
Thermostat operation runs throughout the day. Hot available any time
Cost to operate recirculation pump?
Using the timer and running Autocirc 1 hour a day costs between $11 and $17 per year to operate.
Run autocirc 2 hours a day is $22-34 per year.
Run 12 hours a day costs $11-17 per month, or $132-204 per year.
This includes pump operation and additional time that water heater operates. See calculations

Cost to operate

See larger

Direct return/ probably saves money

Does not use cold water line
Requires dedicated return line connecting to water heater drain port
Saves money since water is not wasted waiting for cold to arrive

Direct return connects to water heater drain port.

How to remove drain valve
Different type of water heater valves
How to flush water heater

Larger image  

Add air vent/ probably saves money

Add air vent to keep air out of line will prolong life of pump
Keeps air out of water line
Smoother flow, less noise

Air vent at Amazon
Air vent at Amazon
Re-circulation install/ maintenance tips
Troubleshoot recirculation pump

Swing check valve

Swing check valve

Check valve that swings open when water passes one direction.
And swings closed when water tries to pass other direction.
One way valve: Lets water pass one direction, but not other direction

Why is this important?

Recirculation system loop can draw cold water into hot pipe causing cold flashes during shower. This occurs during heavy use periods.
Read more
Bad swing check valve can cause crossover, where cold enters hot pipe and hot water never arrives at faucet: Crossover
Swimming pool, or outdoor ponds: If water hose is left in pool or pond or puddle of water, then water use inside home can draw this unsanitary water back through water hose and into home water pipes. Install swing check valve. Do not leave hoses on ground. Or in pool.
Swing check valve at Amazon

Immersion heater
Objective: now guests can stay in the barn
Put 120V electric heater in bucket of water > makes 150 hot water

Immersion heaters at Amazon
hot water dispenser
Hot Water faucet/ dispenser
Objective: save water, save energy
Point of use hot water

Kohler hot water faucets at Amazon
Franke hot water dispenser at Amazon
Kitchenaid hot water dispenser

Point of use water heater
Objective: save water and money 
115 Volt, 2-1/2 Gallon point of use heaters available at most home centers
Connect heater to cold water line
Use switch or timer
Point of use water heaters at Amazon
How to install point of use water heater
Pot heater
Pot heater/ hot water dispenser
Objective: Fill pot for hot water at any sink
12" tall heater heats plugs into 115V outlet
Dispenses 2-3 liters hot water into cup or sink
Use switch or timer
Hot water dispenser / pot heater at Amazon
Sunbeam hot water dispenser

Other Hot water options for sink

Autocirc timer dial

Larger Autocirc image
Auto circ installation manual
Taco 265-3

Taco 265 DIGI timer

DIGI cross reference w/ FM1D
DIGI 240V manual
Taco timer sell sheet

At Plumbersurplus
Taco recirculation at Amazon

Operate recirculation system remotely

Demand pump: Chilipepper
Objective: Water circulates to faucet quickly when activated

Install under sink.
Install countdown timer or operate remotely, etc

Taco D,mand

Objective: Water circulates to faucet quickly when activated
Off delay timer for recirculation system
Off delay timer for recirculation system

Operate recirculation system from 2 different locations

Max load on off-delay timer is 1 amp.
120Volt 100 watt light bulb = .83 amps
Volts x amps = watts
Must use contactor

How it works:
Push doorbell button. Activates timer. Timer turns ON and begins countdown. Timer terminals 1 and 2 are opened. This causes contactor coil to energize. Circuit to recirculation pump is ON.
When countdown expires, terminals 1 and 2 are closed, contactor coil is de-energized, pump turns OFF.

Buy project materials:
Example 50' thermostat wire at Amazon
Example 24 Vac transformer at Amazon
Contactor with 120Volt coil At Amazon
                 More contactor illustrations
15 second to 300 second off-delay timer at Grainger
                 More Dayton off delay timers
                 More off delay and pin timer illustrations
Push button plate Amazon
Grundfos website
Grundfos assorted manuals

Grundfos service centers
Terminal strip and capacitor replacement/ pdf
Sample manuals below:
UP-043 installation photos
Choose pump size sheet
Grundfos product list
Grundfos 24 hour programmable clock
Grundfos clip-on thermostat control

Grundfos contact us

Laing AutoCirc Pump residental selection guide
Laing ACT install operation manual
Laing E1 E3 E10 series installation
Laing E1 Replacement Parts
Taco recirculation pumps manual
Taco timer sell sheet
Taco analog/digital timer install/program manual
Taco timer image

Troubleshoot recirculation pump

Misc manuals and links/ Resources

Grundfos recirculation pumps at Amazon

Will recirculation pump work on Tankless heater?

Yes if you select correct recirculation pump.
   Tankless water heaters require minimum flow rate to activate burner, so more powerful recirculation pump is needed.
Laing UCT-909 Tankless AutoCirc is used for Tankless Buy At Amazon  Resource: Product Sell Sheet and specs
Grundfros RCP-96 Recirculation pump for Tankless 145 psi.; 0-25 GPM At Faucet Depot
Rheem tankless recirculation illustation
Rheem tankless recirculation illustation 2
Rheem tankless point of use illustration
Rheem tankless recirculation illustration

   Read tankless manual thoroughly for minimum flow rate since flow rate appears in every tankless troubleshooting section.
   Flow rate and performance figures apply only when Tankless unit is new.
   Tankless cannot be exposed to hard water or parts will fail.
   As tankless ages, expect problems that are difficult to diagnose and expensive to repair.
   Re-circulation pumps are also susceptible to hard water and affects of age.

Read Bradford White side-by-side tankless vs tankless test results: "Tankless falls short of payback and cannot be exposed to hard water.'
Read ConsumerReports.org side-by-side test results
Pro-n-con tankless heater
Read research pdf on Tankless/Tank efficiencies and softened water: Tankless cannot be exposed to hard water or parts fail 2 years.

How much does it cost to operate Autocirc?

Using the timer and running Autocirc 1 hour a day costs between $11 and $17 per year to operate.
Run autocirc 2 hours a day is $22-34 per year.
Run 12 hours a day costs $11-17 per month, or $132-204 per year.
This includes pump operation and additional time that water heater operates.

Calculate cost of running recirculation system

Autocirc is 33 watts each time motor operates
Timer runs 2 half-hour periods per day > yearly cost for re-circulation is $11-17 at Today's Rates

Two factors affect cost:

1) Pump cost: Pump uses approx 30 Watts = .030 Kw
Pump runs 1 hour per day = .030 Kwh per day
365 days x .030 Kwh = 10.95 Kwh per year
10.95 Kwh x Todays Rate 10 per Kwh (expect 30 tomorrow)= $1.95 per year

2) Water heater cost from re-heating water:
Amount of water: 1.2 gallons per 100 ft 1/2'" pipe (see calculation to right)

Amount of wasted heat:
Hot water travels to faucet anyway, so waste equals return length of pipe
Exact calculation would factor insulation, temperature of water, effect of home HVAC, efficiency of water heater, water heater thermostat setting, cost of energy.

Additional water heater Cost: Reheating 1-2 gallons uses .2 Kwh of electricity per event See chart
2 events per day x .2 Kwh  x 365 days per year = 146 Kwh per year
146 Kwh x 10 per Kwh = $15 per year for electric heater, $9 for gas

So $9-15 per year for reheating + $2 to run pump = $11-17 per year for re-circulation system that runs 1 hour per day assuming new equipment and optimal conditions, and today's low energy prices.

Read more
Calculate gallons inside 100' pipe:
1 gallon = 231 cu inches
Inner diameter of 1/2 pipe .54" so r radius = .27"
Area = πr

A = 3.14 x .27 x .27 = .229 sq in
100 ft = 1200 in
1200 in x .229 sq in = 274 cu in
274 cu in
231 cu in per gallon = 1.2 gal

3/4" pipe: r radius .37"
A = 3.14 x .37 x .37 = .429 sq in
100 ft = 1200 in
1200 in x .429 sq in = 514 cu in
cu in 231 cu in per gallon = 2.2 gal

How to install gas water heater

How to clean water heater

Troubleshoot electric water heater

Programmable water heater timer on wall

Anode rods
Gas and electric water heaters Support the economy:
Buy water heaters  from my associate links:

50 gallon Gas water heaters at Amazon
40 gallon gas water heaters at Amazon
50 gallon Electric water heaters at Amazon
40 gallon electric water heaters at Amazon
Hybrid / heat pump/ water heaters at Amazon

How to install gas water heater
Troubleshoot gas water heater
Troubleshoot electric water heater
box timers Compare box timers
programmable timer Compare programmable timers
Countdown timers Compare countdown timers
Compare power packs

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