Two Energy-Efficient Ways to Get Hot Water Faster - Fine Homebuilding

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Two Energy-Efficient Ways to Get Hot Water Faster

comments (21) February 16th, 2009 in Blogs
Recirculation systems are practical, whole-house solutions for providing instant hot water.Click To Enlarge

Recirculation systems are practical, whole-house solutions for providing instant hot water.

by Scott Gibson

Time-and-Temperature Recirculation

Equipped with both an adjustable timer and an aquastat that monitors water temperature, this type of recirculation system pumps hot water into the supply loop at designated times of day.


• Reduces wasted water and eliminates the wait for hot water.

• Adjustable to specific hot-water needs of the household.

• Override function allows system to be charged with hot water at any time.

• An overused system can increase net energy use significantly.

• When plumbed as a retrofit at the faucet farthest from the water heater, system may warm cold-water lines.

On-Demand Recirculation

This type of system uses a pump to operate only when someone wants hot water. The pump can be activated manually, or automatically by a motion detector.


• Reduces wasted water and the wait for hot water.

• When used properly, can reduce net energy use.

• Retrofit system has less significant crossover of hot water into coldwater lines.

• It’s not always instant. There still can be a wait for hot water after the pump has been activated; length of time depends on plumbing configuration.

• Retrofits require a pump and a power source at the end of each hot-water loop.

Read the complete article...
Hot Water Now
Recirculation systems eliminate a long wait at the tap and save thousands of gallons of water
by Scott Gibson
Get the PDF


posted in: Blogs, green building, kitchen, plumbing

Comments (21)

Dr_Deluke Dr_Deluke writes: I also reccomend the Hot Water Lobster Instant Hot Water Valve...been using it for over great...The Hot Water Lobster Instant Hot Water Valve is a patented design, which incorporates the flexibility of an adjustable temperature control with quality materials and workmanship for a long maintenance-free life and easy installation (not requiring electrical wiring, timers or perishable and noisy pumps)...came with everything needed for a simple “do it yourself” installation (less than 20-minutes).
Posted: 1:17 am on April 5th

Quikflipper Quikflipper writes: When we flip a house we install a Redytemp TL system. This way the new homeowners can select temperature how convenient and efficient/inefficient their hot water system operates. They can choose on-demand mode, timer mode or both. The builtin check valve and the solenoid valve prevents hot water bleedover into the cold water side so owners don't have the waiting for cold water problems we experienced with other circulators. Installing push-buttons at multiple stations is simple enough using the systems RJ11 phone jack. The TL systems use stainless steel TACO pumps which satifies our lead free requirements.
Posted: 5:55 am on May 4th

Bill357 Bill357 writes: Recirculation systems are great, but pumps have always caused me problems. They usually don't last. I recommend a Hot Water Lobster Instant Hot Water Valve. It's a recirculation system that's pump free, creates no noise, and uses no electricity! I installed this thermostatically adjustable recirculation valve under the sink farthest form my water heater and now I have instant hot water throughout my entire condo. It saves time and energy while also saving water! No more waiting water down the drain while waiting for hot water! The Hot Water Lobster is only $179.95, has a 10-year warranty, uses your existing plumbing, and is very easy to install. It only took me 10 minutes. I bought one for my home and another for my cottage. It is great that I can keep my furnace off at the cottage during winter and not worry about my pipes freezing! I've had both units for 3 years now and am very impressed.

Here's their site:

Posted: 9:52 pm on March 31st

TerraLogos TerraLogos writes: Demand Hot Water circulators are GREAT Retrofits if you wait for hot water.
1) Put one under the most used bathroom vanity. Connect to hot and cold faucet risers with 2 Tees. No plumber required, only an adjustable crescent wrench and tube cutter.
2) Plug the pump into the GFCI outlet.
3) Push the doorbell button for a short (20 to 90 seconds) pump run. When the motor stops, hot is HOT and cold is COLD. The shower and any other fixture on that water riser now has hot water.
Not a drop, cold or hot, is wasted.

I am very happy with my 2 year old Chili Pepper. It definably saves water and and it hard to imagine it does not save electricity - lost after the shower gets hot and before I notice it.

Look at RedyTemp and Chili Pepper. I don't see others that are as popular.

I really don't like the timer pumps (Grofundos?). I get how they work but I don't see the convenience or energy savings. And they do require a plumber, and perhaps an electrician.

Posted: 8:30 pm on February 19th

beertruck beertruck writes: LTB,

This old-timer respects and thanks you for time and input.

Posted: 10:02 pm on February 18th

LTB LTB writes: DBDB,
I just happened on a subject I felt like I had some experience I could share. I have a small remodeling business and have a Master Electrical & Master Plumbing license. I specialize in kitchen & bath remodels and basement finishes. I haven't seen it all but I've been part way around the block in the past 30+ years...
Part of the trade off is the cost of the water & sewer processing charges, the wasted water down the drain while waiting for the HOT water to get to your faucet and the cost of gas or electricity to re-heat the water because of the heat loss through the piping. Then there's the convenience and comfort level. I agree that the domestic water heater is the biggest energy waster in your home. That is the reason I have continued on this blog to emphasize the use of pipe insulation. PEX pipe also has less heat loss through the pipe walls than copper. Like all insulation more is better to a point. So use the 1/2" wall foam pipe insulation instead of the 3/8" wall.
I hope you find some of this information helpful. If not, I'm sorry. All it has cost you is your time to read this blog. Good Luck.
Posted: 8:19 pm on February 18th

DBDB DBDB writes: Aren't all these systems generally energy inefficient, especially compared to alternatives such as proximity on-demand systems?

LTB, you have lots of good advice; are you working for FHB or just generous with your time?
Posted: 11:22 am on February 18th

LTB LTB writes: garycrawford,
You could use the supply or return to heat the floor. I would suggest a separate system though. The in-floor heat temps do not need to be much warmer than 105 degrees. Your return domestic water supply could be warmer than that. Unless you use a tempering valve to keep the water temp blended to keep the temp down (complicated). You will also need to make sure you are using Cross-Linked PEX pipe designed for fresh water in-floor heating. I suggest a separate piping system with a separate heating source for the in-floor piping. It is important with an in-floor system that the air be removed. Plus you will need a pump to push the water through the piping (friction loss). Most in-floor circ systems operate at 30psi or less. Your house water pressure should be at least 50 psi. Don't Do it...
An option would be to heat the floor cavity under the floor with the return water. Looping the return line back & forth in the joist space just below the floor. Insulate the bottom & ends of the joist cavity. Install a by-pass valve system with ball valves so you can by-pass the floor in the summer. The by-pass system would help temper the water flowing under the floor, too.
There are several electric cable systems that you can install under the tile that work great, too.
Good Luck.
Posted: 11:03 am on February 17th

LTB LTB writes: glenf,
The check valve at the water heater keeps the cooler return loop water from flowing backwards in the recirc line. Without the check valve the water could flow backwards. Use a SWING check valve and install it in the horizontal position near the water heater. Look at my piping description elsewhere in this blog.
Posted: 10:36 am on February 17th

LTB LTB writes: beertruck,
I have seen the "Just Right" made by NIBCO and they do work. I prefer the gravity flow piping system I had described elsewhere on this blog. The garvity flow system may not work in all applications. The "Just Right" is less expensive than using an elec circ pump. Depending on your water conditions the venturi could plug. I would suggest installing ball valves on each side of the "Just Right" unit as well as union type connectors so you could remove it for inspection. I suggest installing ball valves on both sides of a circ pump, too. When you have the walls open during your remodel I suggest insulating your hot water lines. Be sure to use a anti-scald design shower valve. Some of the better valves also have a temp control device built into the valve. It will keep the water temp where you set it. Since you will have "INSTANT" HOT water at your shower valve, it will be at the desired temp instantly, too.
Posted: 10:29 am on February 17th

LTB LTB writes: plankowner,
You could add a small (6 gal) electric water heater to your system. Leave the elec heater thst set at the factory setting of 125 degrees. You can install the small water heater close to the On Demand heater or closer to the point of use. I installed an On Demand heater for a customer and because of the venting requirements of the On Demand heater I had to install it on the far end of the "tuck under" basement garage. I installed a 6 gal elec heater where the old 40 gal gas heater had been. I piped a recirc line w/ a Laing circ pump to the On Demand heater. The old gas heater had been install right under the 1st floor Master bath and the 2nd floor main bath. So the HOT water to the Master was very quick. The On Demand heater only heats any new water entering the hot water system/loop. The elec heater only keeps the water in the loop warm/hot. There is no lag or dip in the hot water supply temp to the faucets because the circ pump keeps the loop hot. I insulated all the water lines from the On Demand heater to the elec heater. You can also install a gravity or pump loop from the elec heater to the furthest faucet. Look at my gravity flow recirc description also on this blog. You need a small tank to make the gravity loop work. Most On Demand gas heaters will not fire with the small recirc flow rates. I use the NORWITZ brand of On Demand gas heaters, they respond quicker to low flow rates than some brands. NORWITZ owns more than 50% of the World's On Demand market. The 6 gal heater could be 120v or 240v. The Laing circ pump uses about 40 watts of power, has a brass body and ceramic impeller. Depending on your water conditions be sure to clean your ON Demand heat exchanger as recommended by the mfgr. I hope this helps answer some of your questions. If you have more send me your email. Good Luck. Like it or not this will keep you in HOT WATER... :-)
Posted: 10:02 am on February 17th

plankowner plankowner writes: I have a technical question, if anyone can help.
I have an on demand system and has worked for me pretty good so far, but the only problem i have is waiting for the furthest area in the house from the on demand system to empty out the residual cold water in the line as it replaces it with hot water. Which is really not that much, but I would like to use and not waste if I can.
I know about the 1-2 gallon water heater that can be installed under the sink, but that would add to my electric bill also.
Since my inlet well pressure into the system is higher than the bathroom residual cold water left in the pipe supplied from the on demand hot water heater, I would think that that pressure would flow against the residual pressure if I was to put a loop back line going back to the systems supply from the well, which would hinder the proper operation of the whole system.
Does anyone know if they make a type of thermostat valve that can be placed inline with the water coming from the on demand heater to the bathroom, and when the water is hot enough, it opens up to allow the flow to the shower or sinks? The other question would be, how would the loop be set up so that when I open up the faucet or shower, the on demand system senses the flow of water to activate the heater to go on?

Posted: 3:02 am on February 17th

garycrawford garycrawford writes: I want to carry the system one step further. I want to use the return hot water to heat the tile floor in my new bathroom. Suggestions??
Posted: 1:27 am on February 17th

pablocollins pablocollins writes: My family loves the new recirculator I recently installed. Two bathrooms were 25 feet - horizontal - and two other were over 60' from the water heater. In the crawlspace I tapped into the 3/4" hot water line at about 45'from the heater, and ran a 1/2" return line back to the water heater. Hot water now appears in seconds rather than minutes. I installed a Grundfos recirculating pump with a timer and aquastat--- Running only morning and evening it uses very little electricity and the water savings is many gallons per day. My swing type check valve failed after only a few weeks making for erratic hot water supply. I replaced it with a spring type check valve and had no further problems. Total cost was probably a bit over $300 and 5 hours of my time. Well worth it!
Posted: 10:49 pm on February 16th

LTB LTB writes: beertruck,
If 8 ft is as close as you can get then it will have to do. A connection in the attic would be better than making a connection down at the faucet level. The Hot water will rise to the highest point and the cooler water will fall/circulate back to the water heater. I am assuming the water heater is in the garage not the attic. You will have cooler water from the point in the attic to the point of use faucet but the water will get HOT much faster at the faucet than the way it is now. I forget that in several parts of the world houses do not have basements. Email me if you have additional questions at:
Good Luck,
Posted: 9:51 pm on February 16th

beertruck beertruck writes: LTB -

I can't get to the furthest faucet (kitchen) but I can get to the supply line in the attic - about eight feet short of the undersink shutoff. Would it still work??

Most supply lines in attic except where flow to island goes under slab.


Posted: 4:36 pm on February 16th

LTB LTB writes: I have installed the pump designed systems and I prefer the gravity design. No pump and no moving parts, just moving water. On a remodeling job or existing home it is sometimes a challenge. I try to insulate both the supply and return line to the water heater. Sometimes if the basement has been finished this is not possible. I use 1/2" PEX pipe and fish the pipe from a tee located near the furthest faucet back to the bottom of the water heater. I replace the drain valve on the bottom of the water heater with a 3/4" brass nipple and tee and install a new boiler drain valve. I install a "SWING" check valve horizontally near the bottom of the heater tee with the "ARROW" pointing towards the bottom of the heater. I install a stop & waste type ball valve and then connect the PEX pipe return line. I close the ball valve and turn on the water. After bleeding the air out of the hot water line at the furthest faucet, I close the faucet and open the bleed port on the ball valve. When the air has bled out of the return line I close the bleed port and open the ball valve. Now you have a continuous hot water loop and the water is hot to all the other faucets along the line. Insulating both the supply and return lines are important to saving water heating costs. New home project are easy and everyone should do it. You can also install to additional faucets not just the furthest faucet.
Posted: 4:17 pm on February 16th

akphoneguy akphoneguy writes: A long while back I lived in a house where, apparently, the one handle mixing valve in the 2nd floor bath/shower was open internally so the hot&cold crossed over sort of like the Just Right. Cold water fell back to the HWH, hot water followed it down. The HW was boiling hot, so was the cold, not a good situation.
These systems seem to me to mostly be of benefit for those who have scarce a/o expensive water (and no grey water recovery). Where I live energy is the bigger issue and any extra energy load is a negative. The on demand system seems more conservative energy wise; will most homeowners really understand how to re-program their time&temp recirc system to max advantage? No mention here about strategic use of small on demand HW heaters in conjunction with larger HW systems, so that the demand for small amounts of sink HW are met that way. (On demand systems can be time controlled too!)
Posted: 4:03 pm on February 16th

ccaero ccaero writes: Don't forget the possibility of installing a 1 or 2 gallon electrical water heater under that distant bathroom sink. That has served us well for years, and adding the needed wiring was much easier than adding the second half of a pipe loop.
Posted: 4:01 pm on February 16th

glenf glenf writes: So when you open the furthest faucet what keep cold water from the supply line from going up the return line? 30 years ago I had my plumber rig up a system like this in the home that I was building and I don't think that it helped at all! YMMV!
Posted: 3:32 pm on February 16th

beertruck beertruck writes: Have any of you looked into the "Just Right" mechanism??

I am just beginning two bath remodels and am planning to use it.

Posted: 2:16 pm on February 16th

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