Water Heaters - Instant Hot Water Recirculating System?

Our master bath is far from our water heater. The wait for hot water is long and wasteful. At a big blue hardware store I saw a "Watts Instant Hot Water Recirculating System." This system claims to provide instant hot water and thus saves thousands of gallons of water a year and eliminate the frustration of waiting for hot water. First, how difficult is it to install? Are there issues I shoud be aware of? Does it work as well as the packaging claims? The Model number is 500800 for this particular unit. Thanks

There are what's called, on demand hot water tanks for bathrooms and kitchens. The product that you mentioned appears to make your current hot water tank operate as if it were an on demand tank. I've never seen one of those before but it's certainly interesting.

With that product you install a pump by your water heater in the hot water line. Then install a bypass under the farthest sink that allows the water to flow back to the tank through the cold water line. I would think if you have done some plumbing before it should be a pretty install. You will need a power outlet close by to power the pump. (likely a GFCI one) I really don't think you will save much, if any, money though. With the cost of the unit, a slight increase in heating hot water, and depending what you pay for water, it may take it many years to pay for itself. Look at it as getting the convenience of instant hot water.

I have never installed one or known anybody that had one but my brother was looking at them too. If you do pull the trigger on it let us know how it works.

The unit you reference runs on a timer and is installed at the water heater.

The one you actually want uses a bypass sensor and pump installed at the farthest fixture that cycles the pump based on water temp in the bypass tube. Neither of the big box stores sell this type.

UC-303-B (http://www.lainginc.com/UC-303-B.htm)

I had a Grundfos recirculation pump with a dedicated return line and a timer but it had two problems:

1) Most of the time the pump is running, it is not needed
2) when Hot water is needed, the pump is often not running.

I solved the problem with a unique "on-demand" control that turns on the pump when the hot water anywhere in the house is turned on.

http://i480.photobucket.com/albums/rr167/PRYGAARD/RecirculationControl.png

1) On the cold water IN on the Hot Water tank, a flow switch is installed that turns on when it detects flow. (Note: This can *not* be anywhere in the circulation loop)

2) A Delay-Off timer turns the pump on immediately when the Flow Switch turns on, but does not turn off the pump for a while after the flow switch is turned off. (The delay time needs to be adjusted for the characteristics of the particular installation. Typical times range from 30-90 seconds)

3) An aquastat is used to turn off the pump when the farthest faucet in the loop reaches temp.

When the hot water is turned on, the pump comes on and hot water arrives very quickly (but not instantly). The innovation is this: Turn the hot water on for a second and then turn it back off...and the pump keeps going for a while. Then just wait for a little bit and turn the Hot water back on...it is hot and ready to use. After the water is turned off, the pump will run for the delay time and then stops till the next time there is demand.

The parts I used for the controller are:

Flow Switch: Gems 26605 (I got it cheap on ebay). (http://www.gemssensors.com/ApplicationSearchResults.asp?nQuestionID=36 ) Others are available, but be sure to get one that has a fairly low trip point on the flow. (.75 – 1 GPM)

Delay off Timer: MX046 timer kit. (15 second to 6 min delay)
(MX046 Delay Off Switch (http://www.bakatronics.com/shop/item.aspx?itemid=466)) It is inexpensive but you must build it into a case. There are other delay-off timers and relays available but this seems to be the cheapest option.

Aquastat: Grundfos 1/2" Clip-on Control 115 volts #595443.
(Aquastats / Hot Water Temperature Controls (http://store.waterpumpsupply.com/aqhotwattemc.html)) Get the ¾ inch if that is what you need for your pipes.

I put a recirculating system in my house about 20 years ago, and installed one for a neighbor down the street a couple months back.

As was mentioned, the unit that jjjedlic is talking about has a timer. Not the best way to go. Too many times water is getting run through the pipes when it's not needed and will cool off, increasing your water heating costs too much. Instead, I installed a 30 minute wind-up switch in each bathroom (the 2 switches are wired in parallel) to control the pump. I'm on a raised wood floor, so installing the return line wans't that difficult. Plumbing is as prygaard's diagram shows, except I have a second check valve on the incoming cold line where he shows the "flow detect switch". And I don't have the "aqua stat" either. Just tee into the hot water line under the shower valve.

I used essentially the same pump that jjjedlic is talking about, but got it at a plumbing supply where it can be purchased without the timer. It only uses about 23 watts when it's running, and it only takes about 15 to 20 seconds to get the hot water through the 60 feet or so of pipe between the WH and the shower valve farthest from it. It doesn't save energy, but it DOES save water, along with the convenience of not having to wait for hot water. With the wind-up switches controlling mine, it only runs when it's need and I don't have to worry about it ever getting left on.

I'm on City water, but that's expensive enough. If I were on well water, it would save even more because I wouldn't be paying to pump the water that is getting run down the drain waiting for the water to get hot.

Wouldn't trade my recirc. system for the world, and in 20 years of being used virtually daily, it has paid for itself about twice in water savings.

prygaard, :thinker:

Way to go! Your concept is almost exactly what I was thinking and how these things should really be built. I was thinking I needed individual flow switches, but your idea simplifies this to one. My Laing 909 already has a temp sensor so that part is covered. Then the delay timer also makes perfect sense.

The alternative is that I could configure my Home Automation system to manually activate the circ system just prior to water use.

I was just discussing this with our Automation guy and it dawned on me:

Why not just put the flow switch in the hot supply line? As long as you have an aquastat, it will still shut off when up to temp and will only activate if you draw water. Yes the flow from the circ will keep it active as long as there is flow, byt the stat will shut it down when the set temp is reached.

I have a Laing 909 tankless which has a stat and a timer.

The main thing the delay-off switch does for you is allows you to momentarily turn on the Hot Water to get the system going. You can then turn off the Hot water for a few seconds while the pump continues to prime the system. Without the Delay-Off timer, you would have to leave the water running till it is hot...and that would waste water. Granted, the amount wasted is considerably less than without the pump, but every little bit helps when you are in a water 'poor' area.

One other point: I am not completely satisfied with the clip-on aquastat I am using. It is rather slow in reacting so the pump has to run for longer than I would like before it kicks in. I am looking around for another type of aquastat that would be reasonably easy to install, low cost, and faster reacting. (picky, arn't I :) ). In another forum a gentleman suggested I will have to use an immersion aquastat...but I have not found one of those that I like enough to put the money out for.

TD MAX
I just re-read your post. I did not get your question the first time, but the second time I read it I did. I like it!!! The problem is that the clip-on Aquastat I use does not react as fast as I would like for this type of set-up.... This means the pump would run for too long each time it comes on. However, even with the slower aquastat...it would be an easier job for us DIY'rs. (I spent a fair amount of time building up the controller case)

Now you *really* have me thinking about how to do a better (low cost) Aquastat. Between us...we might come up with a really great simple and effective solution.:thinker:

Thanks for the idea..... It is one of those "Why didn't I think of that?" ideas.

Great Job.
Paul

Paul

TD,
I thought some more on your idea. There are a few things to think about if you set it up:


The pump flow must be great enough to activate the flow switch. This probably means you want to stick with a .5 GPM Switch.
To 'Activate' the system, you will probably have to leave the Hot Water on a few more seconds (till the water is flowing from the pump enough to activate the flow switch). This also means you want to stick with a .5 gpm switch.
As mentioned before, it needs a fairly fast acting Aquastat


I don't think any of the points above will kill the idea...the system just has to be designed right.


I still really like the idea. The simplicity makes it elegant!! A toast to you!! :beers:

BTW: You do realize you have ruined one of my saturdays while I try this out!!!:D

http://i480.photobucket.com/albums/rr167/PRYGAARD/SimplifiedFlowcontrol2.jpg

I may should have mine up and running tomorrow if the flow switch shows up. Ours is a new home so I'm working with the plumber and electrician rather than messing with their work.

Look at: Johnson controls 419 temp control module. It has an immersion aquastat. This gets us part way there, but has no flow switch capabilities.

Looking further at the manual though, it allows an aux input to cause a 50 degree offset. I plan to set the temp at something low like 70 with say a 5 degree differential and use the flow switch to activate a 50 degree offset causing it to run until 120.

I'm not sure that it will work as planned, but I'm going to try. The latency of the electronics is a big wild card...

TD,
Please keep us posted. I have not had a chance to re-configure the set-up with your idea, so I am very interested in your results!

Thanks
Paul

In looking at the Dia., a question comes to mind; wouldn't the Recirc. pump have to be strong enough to overcome system Pres.?
I think my system Pres. is something like 80 t0 90psi. Even with a valve open (with water savers ect.) it might still be close to that. Are these pumps hat strong? Thanks.

mohave2952,

No -- the system pressure isn't an issue because the pressure is the same on both sides of the pump. The pump only has to move the water through the pipes, which happens very quickly.

I doubt that your system is running at 80 to 90 psi. If it were, you would probably be experiencing some problems like a leaky T&P valve, pipe hammering, etc. If you think it's that high, buy a $5 pressure guage from a local hardware store and check it. There is no reason to have more than 50 to 60 psi, and more than that will create problems.

OK, I got it. Also you're right, there is a Pres. Reg. on the supply line. Thanks

mohave2952,

Even at only 23 watts of power for the pump, they DO move the water very quickly. I have about 75' of hot water pipe (about a third is 3/4" and the rest is 1/2") between the WH and where the return line of my system ties in below the shower in the master bath. There's about 50' of 1/2" return line going back to the WH. First thing in the morning, it takes about 30 seconds for the pump to get hot water to the shower. Without the recirc system, my neighbors are running water for almost 3 minutes to get hot water to the same shower. (I'm in a tract home, and we all have virtually the same floor plan.) The neighbors are running their water down the drain -- paying for it because the make up water has to run through the water meter. I'm just running mine in circles through the pipes. In the 20 years my system has been in place it has paid for itself 2 or 3 times over in water savings. At only 23 watts for the pump, running it 30 minutes a day, it's using about 25 cents a YEAR in electricity.

TD,
Please keep us posted. I have not had a chance to re-configure the set-up with your idea, so I am very interested in your results!

Thanks
Paul


Sorry for the delay. My setup is up and running. Works OK, but I could use some more "push" with the tankless water heater. It takes about 3.5 minutes to circ to temp setting. Not bad, but I'd say that's only around 2 GPM.

If I just start and run the farthest faucet it only shaves temp time from 1:45 to about 1:15-1:20 which is not enough for me.

Thinking Taco 009 cartridge circulator which should more than double the flow (5 vs 2gpm) of the Laing at 20' of head.

If you'd like some further details you can find my email link at kennedy diesel dot com

I'm considering implementing a similar demand set up with my tankless 94ls to save water, provide hot water at faucets with less than .5 gpm (assuming pump would recirc and kick on heater), and eliminate coldwater sandwiches (assuming pump would continue flow as set by delay timer.

I had thought of using a small 8 gallon electric water heater immediately downstream from the tankless and wiring a pump to its thermostat so that whenever its temp falls it kicks on the pump. The main difference here is that I'd still have to waste a bit of water to get the pump going, so I'm leaning towards a solution like Pryygard's.

Thoughts and advice?

TD was your set up successful?

Thanks,

Adam

Adam,
I was away from the forum for a while. Sorry

I do not understand the design you propose. (I am probably missing something) If the pump is only controlled by the thermostat on the small tank, it would kick on and off all the time...but may not be on when you want HW at the faucet. The water would probably be warm most of the time... but may not be hot unless the pump happens to be running. (The water in the small tank will probably cool off slower than the water in the pipes).

Were you thinking of adding any other controls to the pump?

Paul

If this is a new install, you can also very easily add a gravity fed recirc loop. No power need. No controls. Just good old gravity.

The basic idea is pipe a loop the farthest fixture. The piping should slope just slightly upward toward the farthest fixture. Then at the farthest fixture, pipe vertically and then work your way back to the hot water heater, and trying to slope it downward. The return piping can be much smaller in diameter. You only need a trickle. Connect this back to drain on the bottom of the water heater. Unscrew drain valve, add nipple, tee and then thread drain valve back. Return line comes back to the tee. I also add a ball valve in the return line so that I can throttle the flow to just enough. You insulate the lines and then off you go. As the water is heated, it travels up the pipe to the highest point, this water then cools slightly (cooler than water at the hot water heater) and "falls" back to the hot water heater. This goes 24x7 even during a power failer. Done a couple of these and they work fantastic.

From your original post, I assumed that you were putting in a retrofit recirc, without a dedicated return line. These are easy to put in, and work well, with the one side effect is that you have 80º or so water in your COLD taps for a bit, when first turned on. If you ran the recirc 24/7, you would probably waste a lot of water trying to get cold water from the cold tap! So I would always use a switch, or at a minumum a timer, to minimize this effect.


All the diagrams posted show recirc with dedicated return, which is great. If the house is laid out right, you can often install that as a gravity system...no pump. This can work very well.

The problem that I see with a gravity system is that it's constantly pulling hot water out of the WH and putting cold water back into it. That's like having a hot water leak -- it's causing the WH to operate a lot more than it needs to, which will play havoc with your utility bill.

In the two gravity systems that put in, the increase natural gas consumption was negligible (may been $1 more per month).

The analogy that this would be akin to a hot water leak is not correct. A better analogy is that you are now including hot water piping (to fixtures and back) as part of your hot water heater. This is why you should insulate the pipes (and one of the reasons it is easier to do if new install).

The return water is not "cold" water. It is not as hot as what is in the tank. It is still hot though. You would be surprised how effective a degree or two in temperature difference is in creating flow.

I install a ball valve in the return line so that you can throttle the flow to as much as you want. All you need is a trickle to maintain instant hot water at your sinks. If you have a 40 gallon HWH, think of it instead as a 41 or 42 gallon HWH (counting the water in the hot water loop).

This also operates on the KISS principle (Keep It Simple Stupid - please note, I am not calling anyone stupid, this is just the name of the principle).There is nothing to fail or maintain. By actively pumping and sensing. Something will fail and any gains/savings you made are lost with the first repair.

I always like to have alternatives/options, so my recommendation would be to install the gravity loop and try it out. If not happy, then you can add all the electronics/sensors/pumps etc. Everything that is needed is in place with the gravity.

Just my $0.02.

I would like to install a pump at my hot water tank. I have no return line. I would like the pump to turn off after the water is hot at the target location. It is not pratical for me to intall and aquastat because of existing construction issues. Does anyone have an idea how to turn the pump of automatically? Thanks.

dhomerw1,

Welcome to the forums.

You have to have SOMETHING as a return line in order for the system to work. There are systems that mount below the farthest valve from the WH that use the cold water line as the return line -- pumping the water out of the hot line and into the cold line, which is then recirculated back to the WH to make up for the water that the pump is withdrawing. Those have a thermostat in them so that once it senses that the hot water has arrived, it shuts off so it doesn't put too much hot water into the cold water line.

The alternative to that is to pumb in a dedicated return line, like is shown in the diagrams earlier in this thread and which is what my system has.

But putting a pump in the hot water line near the WH isn't going to do a thing without SOMETHING for a return line. Where's the water going to get pumped to? It has no place to go.

Thanks Lefty. Yes, that was what I was looking at one of those pump systems at HD that has the valve that goes under the farthest sink. My only problem with that I did not want to use the timer on the pump. I wanted the pump to come on autom. when water began to flow out of the hot water tank. I could not figure out how to do that. My best idea was to wire a swith to the pump and turn the switch on when I needed the hot water?

dhomerw1,

You don't seem to understand the function of a recirc pump system.

They are used to get the hot water through the pipes, to the farthest valve from the WH WITHOUT having to turn the water on and letting it run down the drain. It's on a timer or a mechanical switch so that it is turned on BEFORE the water is needed.

That's all they do. They don't increase the amount of hot water available and don't increase it pressure or temp.

Yup Lefty I do understand. I do not want my pump running needlessly. Only on hot water demand, not by using the timer on the pump.

Are you saying with a pump on my hot water tank, when I call for hot water the pump must run even after I have received the hot water and the pump cannot turn off while drawing hot water?

dhomerw1,

I understand that. But you have to have something for a return line in the system, whether it's a dedicated return line, or the style that installs under the farthest valve from the Wh and uses the cold water line as the return line.

To use the system, you turn the pump on BEFORE you actually turn the hot water valve on. The pump recirculates the water out of the hot water pipes (which is cold due to heat loss from not being used) back to the WH and replaces it with hot water. (That takes from about 2 minutes to about 5 minutes, depending on how long the pipe run is and what size of pipe is involved.) Once you have hot water AT THE VALVE, you turn the valve on and have instant hot water.

Turning the pump on WHEN you turn the valve on wouldn't accomplish a thing. The pump needs to come on BEFORE the valve is opened.

so under this scenario, when does the pump turn off?

Depends on how it's turned on.

My system has a 30 minute wind up timer switch in the bathroom. I turn it on for 20 to 30 minutes, and once that timer has run out, the pump goes off.

Other systems have a timer on the pump (or wired to the pump) that is set to come on at a given time and go off at a given time. These have a manual override incorporated in the timer so it can be turned on at sometime other than what is programmed.

The style that mounts under the valve (usually under a bathroom sink) also have a thermostat in them (in addition to the programmable timer) so that once the hot water reaches the pump, the pump shuts off. That prevents the pump from filling the cold water pipes with hot water, since that system is using the cold pipes as the return line.

will a flow valve turn the pump on and off

Not really, and WHY?? You don't need that.

I don't understand why you are thinking that running the pump for a few minutes or even a half hour is going to be a problem. My TACO pump draws 23 watts of power. If I run it for 30 minutes a day, everyday, it takes about 80 days for it to use 1KWh of electricity. That is costing about 10 cents, every 80 days, or about 45 cents a year. My TACO pump has been in my system for about 15 years. My entire system has been in for almost 25 years. And it's saving me about $20 per year on my water bill. Put another way -- the $12 to $15 I've spent on power to run the pump has saved me about $500 in water.

...because I do not have a set time of day I need hot water. It varies daily based upon my lazy schedule.

Makes sense to me -- that's how mine is set up.

I turn it on with a 30 minute windup timer switch. It goes off automatically, as soon as the 30 minutes is up.

You have said that you don't want to run the dedicated return line. I understand that, especially if your house is on a slab. That is going to limit you to the style that connects under the bathroom sink and uses the cold water pipe as the return line.

That style has the thermostat, as mentioned, that shuts it off as soon as the hot water reaches the pump. It probably also has a timer, but THAT you can very easily wire around and control it by a switch.

so the type that installs under the sink, does that have a pump on it at that location?

Yes, that's exactly where it goes. The unit is self-contained -- check valves, thermostat, timer, etc. -- and comes with the necessary supply lines as far as I know.

Well Lefty, that looks like the direction I am goin to go on this. I might kick it around a little more but I think we about got it sorted out.

I have installed most of these except the pressure switch one.

I think it is important to have very well insulated lines to save energy.

I like the dedicated return from the furthest fixture because when you circulate that once, you are not adding cold water but simply moving the already heated water around.

I like to put a switch in the room so that you simply turn the pump on a few minutes before you need it. I use a lighted switch to indicate that it is on so you don't forget it. The timer switch is a good idea that I had not used. If you don't want to run a 120v switch from the kitchen/bath to the tank/pump you can make it a low voltage thermostat wire and a relay at the pump.

When necessary, I have used the cold at the last fixture as a return and put the pump under the sink, but as said above, you are then pushing the cold back to the tank and heating the cold pipes which will cool that water back down as soon as you use cold. And of course it will fight the circulator flow if you use cold.

I have also installed small point of use tanks under a kitchen sink as well as instant tankless heaters. This is very popular in other countries where they put a wall hung heater right in the shower.

thanks for checking in. I have still been thinking about this and have not done anythig yet. What I think I am going to do, is get one of those Watts pumps that go on the hot water tank at HD. Then place the sensor under the farthest sink. Wire the pump to a switch in the bathroom. Set the timer on the pump to on all the time. Control the pump from the switch. Turn on the pump just before I need hot water. I like the lighted switch idea. I shoud probaly add red strobe light so my wife does not forget it. What do you think, would this work.

dhomerw1- I'm confused by your post. How would that make you have instant hot water? The pump is going to be running but unable to push any water anywhere. You still have to wait for hot water unless you have a return line.

dhomerw1,

No, it's not going to work without SOMETHING as a return line!

WHERE in the system the pump is physically located makes no difference.

The easiest thing for you to do is to get one of the units that mounts under the bathroom sink. The biggest problem will be getting an outlet wired under the sink so that the pump can get power. You can control that outlet with a switch if you so choose.

But the undersink unit is going to connect to both the hot and the cold water line. It will use the cold line as the return line, so that when the pump is running it will be taking water out of the hot line and moving it into the cold line. The unit has a thermostat built into it that will shut the pump off as soon as the hot water reaches the pump.

Don't try to put the pump in the garage by the water heater UNLESS you run a dedicated return line. And running a dedicated return line means that you'll have to add a couple of check valves to keep the water flowing in the proper direction.

You don't have to worry about that with the undersink unit -- the check valves are in it.