I have never heard of one that is motion activated. How cool is that!?! I'd love to hear from anyone who has this as well. Can it be added to an existing system?

Do a search on the HVAC and Renewable Energy forums, or post this question there. I recall reading a thread over there about one of these - but it was burried under a different subject.

You can also buy recirc pumps that have built in timers so they turn on and off at times of the day you program ( see http://www.lainginc.com/) and that would be easier to install then the IR activated switch. Since these pumps generally consume very little power (mine uses 33 watts to run), running one for a few hours per day might not be a bad solution either. If you ran a pump for 2 hours per day, a 33 watt pump would cost you less than a penny.

Our recirc pump has a timer on it, but since I'm home all day we've never used it and it runs constantly. I didn't realize it was that inexpensive to run! Thanks for the info, sniff. :o)

Note that all pumps are not created equal. The Laing pump I provided the link to is 33 watts. Others may be higher but in general - the recirc pumps are low head (low friction), have tiny motors, and do not require a lot of power.

My electric rates are a maximum of 11 cents, loaded cost with all fees and taxes in the summer, per 1000 watt hours (run a 1000 watt light bulb for 1 hour, cost is 11 cents). So a 33 watt pump consumes a total of 792/1000 kilowatt hours whicn means I can run my pump all day for about 9 cents.

I would still put a timer on it if I could (every penny counts) but I had to add my recirc pump in after the fact (when we discovered just prior to move in that it took 5 minutes to get hot water to the distant end of the house!) and a timer would not work for me (long story).

The IR switch is nice and would be a fun project, but it might not be worth it when you look at the cost of your time to install it vs the cost to use a pump on a timer.

If you happen to have a recirc pump upstairs in a bathroom it is a lot easier to install the IR activated switch (some people have posted that they use a push button switch in the bathroom to start the pump). But many of these recirc pumps are located in the basement (near hot water supply), and in many cases the issue is getting hot water quickly to a bathroom upstairs. So running control and power lines from switch to pump in these cases might not be easy and therefore the timer might work best.

Here we go again. Pumping hot water to lose heat in your pipes 24/7 is absolutely not pennies a day. The pump energy use is the least of your concerns. Taking hot water out of your tank to marginally insulated pipes all over the house will cost you in whatever you use to heat pipes. I was talking with a supervisor (of home construction) who said that his gas bill for hot water (ie in summer) was about $50 when he remembers that it ran around $20 before he had the system. He built his house so I am sure the pipes are insulated. I was absolutely surprised by his numbers and maybe it was exaggeration but I believe he did say that he shut it off and looked at the numbers ... but everyone liked it so much that they decided it was worth it.

So don't for a second think this costs pennies a day. Now in a cold climate, some of that heat may heat the house (assuming it isn't in an uninsulated slab or on the outer walls of the house). But similarly, in a warm climate - that extra heat is another load for the a/c.

I've looked into this - our plumber quotes $1000 or so for a 4000 sq feet house with 3.5 full baths. The system has a timer but no sensors. You need return lines and you should insulate (code around here) all the hot water lines. I may do it but only with sensors or other mechanism (you could use the light switch if you could make it work code wise).

Off my soapbox. The "here we go again" is from another forum I think - plumbing probably....

My experience agrees with that of david cary. The cost of operation is not in the electricity to run the pump. It is in the heat loss of the water running unused thru the pipes. Comparing my gas bills in the summer when water heating is the only use of gas for my current 2000 sq ft house against similar situation in my prior 2000 sq ft house of similar construction without the recirc system indicates a monthly cost of $25-$30 per month. I'm willing to bet that cost is significantly more in the winter when the slab is colder, thus more heat loss in the water, but I can't measure it easily because my furnace uses gas and confuses the issue.

Having instant hot water is really nice, but I'm now wondering if I wouldn't have been better off doing away with the recirc system and installing a small tankless water heater near each point of hot water use, ie one in each bathroom and one each for kitchen and utility room. I don't have any experience with tankless water heaters and I haven't done much research. I was just wondering.

I have researched tankless and recirculating. Neither stands up, as far as I am concerned. We are going with quality conventional.

Part of the trick is designing the house so that there is minimal distance between the water heater and the faucets. In our case, the master bath is quite a distance from all the other points requiring delivery of hot water. We have chosen to locate the hot water heater on the side of the house with the majority usage: kitchen, laundry, guest bath, workshop, and powder room. Since hot water will be flowing to the master bath only a couple of times a day, waste heat in the pipes will be minimized.

It's all in how you plan your layout.

muddy

I have tankless and recirc - its all in the implementation. if you run the recirc directly off the tankless - where the tankless untis are actually providing hot water for the recirc loop - then you are hosed.

if you use a small electric tank off to the side - mine is 4 gallons - different story. My tankless never fires up to keep hot water in the recirc loop. The 4 gallon tank uses about 900 watts and keeps the water at about 110 deg. You also have to insulate the entire recirc loop to keep it from cooling quickly. and tying the tank and pump into the water supply has to be done correctlty so that tankless units do not see flow when all sinks are off or it will fire up.

The location of the hot water source is a key factor. We opted to put the tankless in the basement directly under the master bath/suite since that is where we would prefer to have instant hot water (it is actually about a 5-10 second delay even with tankless 10 feet away). The problem is that the kitchen, butler pantry and other utility sinks are almost 100 feet away on the other side of the house. I could have done point of use hot water at each sink, but you need a dedicated 15 amp circuit (sometimes 20 amps/240V depending on the unit) under each sink to power those. Unfortunately, we did not discover the delay issue with hot water until the house was done, so adding another 3 or 4 dedicated circuits under these sinks was not an opeion.

If I could have I would have installed another gas fired tankless unit in the basement under the locations where these sinks are. Problem is that venting with tankless on that side of the house is an issue. That area is also right where my wine cellar and bar are going - so another hot water source would not work no matter what it was.

I would prefer to not have the recirc but DW hated waiting for over 5 minutes for the hot water to flow. I calculated the cost to run the pump, heat the water in the small tank and line, and the savings I get from not running the tankless for 5 minutes everytime I want a squirt of hot water. Total cost is under $250 per year. That might seem high to some, but it is worth it to me since DW is happy.

For tank systems, a timer on the pump will significantly reduce costs. Most of the time the issue is that the master suite is on the second floor and it takes a long time (my old house was 5-7 minutes) for whot water to get up there with the shower on full blast. That is because there was a lot of cold water in the hot water feeder to the second floor that has to be pushed out before hot water arrives. For these cases, all you need is to get hot water into the top of the second floor feeder line 5-7 minutes before you are going to use the shower. Some people put the recirc pump in the upstairs under a bathroom sink. Others put the pump down in the basement near the tank.

If the OP has a pump upstairs and she has the second floor master issue, all she needs to do is connect a switch to the pump so that it will turn on when she wants hot water. A lot of people have posted on the plumbing forum about using push buttons - when they go into the BR in the AM, they hit the button and 5 minutes later the hot water is ready at the shower. Running a pump in this situtation will not cost a lot of money for both the pump and loop with hot water.

Instead of using a push button, one could use a motion sensor switch but I see issues with that. Everytime someone enters or leaves the room - even to just get a tissue - the pump will turn on. But if that is what the OP wants, then use a standard motion sensor switch that contols a switched outlet (instead of a light) in the bathroom. Connect the pump to the switched outlet and you are in business.

You will have to adjust the motion switch so that the power stays on for at least 5 minutes after motion is detected or else the pump would shut off before it pulled all the hot water upstairs. I know that motion sensors have such a setting to keep the lights on for X amount of time - but I do not know if that delay is long enough. You would have to look at the specs for the motion sensor switches to find one with a long enough delay off feature.

if the recirc pump is in the basement, the timer would be the best solution because controlling the ON/OFF from the bathroom with a motion sensor would be much harder. I suppose you could do a wireless approach but that sounds harder than its worth.

I have read some posts about how expensive recirc pumps are to run. This has not been my experience.

We had a circ pump installed a few months ago and our elec bill started going up almost immediately. It's exactly what "David" mentioned up above. Our neighbors (new home built by same builder, at the same time) don't have a circ pump and their electric bill stayed steady while ours climbed by $50/month leading into the winter. After three months we finally thought to record our meter readings and unplug our pump. Our numbers went down DRASTICALLY on days when the pump wasn't running for long (we plugged it in for morning showers or for a hot setting on the washer).

I don't know much about the kind of circ pump that was installed for us, so my experience could be just that, MY EXPERIENCE...but I just remember the plumber telling us that it would only cost us pennies each day to have it plugged it. He compared it to having a lightbulb turned on all day---oh how I wish we would've known.

It's winter, and I have to go out to the garage to plug our pump in if I want to wash dishes in hot water, or wash my hands in warm water, or ANYTHING!

The heat loss from not insulating the hot water lines swamps the cost of running the circulating pumps.

If you put the pump on a timer so it only runs when you are likely to use hot water the costs go down.

In most places water (and sewer) are still cheap enough you can waste a lot of water before it costs as much as the heat loss from the circulating system.

There are motion sensors that can easily be hooked up to turn on a circulating system when motion is detected in the bathroom.

Would you kind people please explain to me what this recirculating pump thing is? We are trying to make decisions about what type of water heater to go with and how to get hot water to all of our usage points quickly.

We have master down isolated on one side of the house. Monday through Friday we take quick 5 minute showers with maybe one long tub soak during the week. Then on the weekends it's long luxurious shower time, complete with body sprays, etc. I think I want a tankless system for here so that I don't ever run out of hot water. Then the other bathroom is upstairs which after my daughter leaves for college in a couple of years will only be used for occasional guest use. The kitchen and laundry are on the opposite side of the house from the master bath.

Originally I thought that we might use a traditional gas water heater for the second bath and kitchen. Of note is the fact that we have very high water/sewer rates here, so it really won't be good to run water and wait for hot water. What do you think I should do and would a recirculating system help us? Thank you.

I'm not an expert on this by any means, but DH had recirculating hot water by convection put in our last custom home, and in the renovation of our current 1916 bungalow. No pumps. It is awfully nice to have hot water when you turn on the tap. Also, having really hot water flow into the dishwasher when it starts up has to be a plus. Have to admit I'm spoiled with this. I do understand that it probably adds to the gas bill; how much, I have no idea. The plumber we used on our last custom home recommended it to us. The plumber for the renovation had no idea what we were talking about (he had done it only with a pump), so DH had to explain how to run it without a pump. I'm sure we'll do it in our new home as well. But definitely make sure pipes are insulated well.

We have a recirc pump that is controlled by a motion sensor in our house.

Actually, we have two motion sensors (two upstairs bathrooms) connected in series to a delay timer. When either detector is triggered, the outlet that powers the pump will energize for 20 minutes. The pump also has a thermostat on it, so it will not run for 20 minutes, only long enough to "charge" the loop.

Our remodel has been a long one, so we had the recirc pump running via thermostat only (ie, pump powered 24/7) for a year. While it varied from month the month, the actual cost of the thermostate-only recirc loop was $15/mo.

With the motion sensors, the cost is negligible. As these are second floor bathrooms, the majority of the time that we go into them, we will end up needing hot water so the "cost" for charging the line is no different than if we did it the old fashioned way (turn on the faucet and let it run for a while). Of course, the hot water is there when we need it now ... not 60 seconds later.

I think it was ~$30 for the relay, ~$15 for each motion sensor, and ~$20 for the misc materials (wire, outlet, boxes, etc).

It is something that we will definitely have in future houses.

ncamy: a recirculation pump draws water from the furtherest point in your hot water system and and puts it back in the water heater. This draws freshly heated water to the pump point, essentially as if you'd run the tap, but the water isn't wasted and less energy is required to re-heat the once hot water than ground water.

In your case, it would save you the cost of a second water heater. Tankless elicits just about as much controversy as politics and religion. How long it takes to pay off the much higher initial cost will depend on energy costs, and I think anyone counting on a long term downward trend of those costs will be dissappointed. Also, if you have extremly cold ground water temps in your area, the tankless may have a hard time keeping up with the demands of a multi-head shower with body sprays.

The idea of a motion activated or push button recirc pump is pretty cool: mine is on a timer. If I lead a really structured lifestyle and showered at the same time every day it would be great. But there's really not a lot of point in the pump heating up the shower at 7am if I'm not going to be ready till 9-- the water in the pipes will be cold again by then.

Since my walls are now enclosed, I may look into a wireless transmitter to control the pump-- Billy Mays to the rescue...

um..... am I missing something here? We have a 3000 sq ft 2 story home, h.w. heater is in the basement. We have instant hot water at every faucet in the house, sinks, tubs, showers, washer, dishwasher..... We do not have a pump, no check valves, no controls but a gravity loop system to recirculate. NO ELECTRICITY USE AT ALL. I'm no engineer, but I'm married to one, he set it up, and it has worked every day, since day one, for almost 20 years.

joyce 6333 - our DH's seem to be the ones who get how this works

dlm2000 - the electricity to run the pump is a minor concern. Here is a link showing a $400/year cost for a pumpless system as you have. A pumped system that runs on a timer, demand or motion sensor will save money over the 24/7 system you have. Mind you, this guy is on propane so a NG system would be cheaper. The water saved around here would save about $50 a year but he had a long run from hot water heater to master bath so it could easily be 1/2 that.

Your husband must not be an engineer that is concerned with energy wastage. My father is one and he thinks such a system is like driving a full size SUV with 1 person and no cargo - oh wait - people do that all day long....

Here is a link that might be useful: Cost breakdown with recirc system

We are going to have two traditional water heaters. We have heard great things about gas tankless heaters, but everyone has warned us to stay away from the electric ones. (No gas available where we are). We will have a decent sized one for the Master and kitchen, and then a smaller one for the girls' bath. I liked this set up because I can keep the temp on theirs a lot lower to avoid accidental burn, and because that heater can be turned off when they leave our house.

I would just like to say that we have wonderful problems/concerns on these forums. We have to remember that not everyone in the world even has access to drinking water, let alone instant hot water! I forget that a lot, and I feel bad that I do.

David_cary ~~ as dlm2000 points out, there is NO pump used on the convection-style recirculating system.

You can probably get a better explanation by googling, but basically what happens is that all the hot water is piped consecutively (and yes, pipes must be insulated, but they shoud be anyhow), but instead of the pipe dead-ending at the last faucet, the pipe returns to the hot water heater. Convection causes a slow journey through the pipes, hot water goes up and cooler cometh down, which results in hot water always being at the tap.

As with any other issue involving moving heat, insulation of the transmitting unit (whether water pipe or air duct) is required for the best energy efficiency. I have no doubt that there is a slight increase in the overall cost of heating hot water, but it should be a *very* slight increase since the water within well-insulted pipes does not drop a great deal of temperature ~~ and if one is truly concerned about energy efficiency, there would be a far better cost return by solar pre-heating the originating water before it goes into the water heater.

meldy nva - I understand exactly how the "pump less" system works - no googling needed. Check the link where he describes a "thermosyphon" system without a pump costing an estimated $400/year - and I believe he has insulated pipes.

It currently is code on recirc systems to have insulated pipes. There is probably not a code issue without recirc systems except on outside walls.

I realize is seems like a lot of money for a pumpless system but heat loss is heat loss - regardless of whether a pump is used or not.

Not to get overly defensive but where in my post does it say that I think he has a pump? By telling me to google something for an explanation - you are basically saying that I don't know what I am talking about. I have been looking at this stuff for just about a year - I quoted a link that clearly describes a non pump situation that I found in about 30 seconds.

Thermosiphon systems have a couple of issues.
The return line needs to be larger than on a pumped system, and they require heat loss on the return side to operate.

The heat loss is what produces the temperature difference needed to drive the circulation.

A pump with a timer or motion system is liable to be much cheaper.

In hot climates, A HRU on the cent A/C works well with a recirculating system. With the HRU, the more heat you can shed, the lower the power bill goes so the 'wasting' of heat actually becomes a cost-saving strategy. A HRU will cut electric water heating bill at least $50 a month for a cost of

david_cary, I apologize for not being clearer in referring to google ~ I meant that one could get a better explanation than any *I* could give; it was not a reference to your [or anyone else's] knowledge.

~~

Has anyone found an unbiased study which indicates how much temperature differential is needed to provide the appropriate convection? My understanding on the hookup is that the return line is tapped back between the incoming [cold] line and the heater, and would thus cause a speedup in the circulation because the water in the return line would be drawn into the tank (before? with?) the incoming cold water. My only personal experiences with convection systems both involved the return line going into tanks set up for solar batch heating which fed into an electric water heater. Actual cash out to heat water was almost negliable in both cases, which gives one nothing to judge by for cost comparisons.

The issue I have with pumpless systems is that water in the pipes is kept at temp -always-, not as needed as with a pumped system. They return a LOT more gallons to the heater for re-heating than a pump running for a few minutes at a time.

With pumpless, every pipe in your home is essentially part of the hot water tank. The best pipe insulation is still far behind what your tank has, and the combined surface area of all those pipes is huge.

"Has anyone found an unbiased study which indicates how much temperature differential is needed to provide the appropriate convection?"

It depends on the pipe friction and height differacne between the various components.
There is no single number for all systems.

"My understanding on the hookup is that the return line is tapped back between the incoming [cold] line and the heater, and would thus cause a speedup in the circulation because the water in the return line would be drawn into the tank (before? with?) the incoming cold water."

Water flow is like electricity flow.
The water will move inversely proportional to the pipe friction.
A check valve is used to make sure the cold water does not flow out on the return line when a faucet is opened, but the pressure source is the cold water line into the tank, so it will supply most of the water.