My dear favorite father in law is looking for a way to speed up the hot water to the faucets throughout his home. I did a google search and came up with a pump with a timer that mounts to the water heater and a check valve thingy that goes between the hot and cold lines at the farthest faucet. The manufacturer claims this is the answer. Anybody used this item? The manufacturer is Groundfos www.rewci.com.
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Grundfos pumps are often used in radiant heat applications, and are a reliable product. They are sold with iron impellers, or bronze, or stainless - the latter is probably best for drinking water. Like the link says, they operate quietly. I find they produce almost no vibrations. The motor housing does get warm when the pump operates continuously, but that seems to be normal for this product. Note that the UP15 pump is rated for up to 3.5' of head, so it won't work well for a second floor bathroom.
I am concerned that you may end up getting quite a lot of hot water at the cold water tap, for quite some time, though the vendor says this is a minimal concern... Is there any way you could install a return loop on the hot side? Doing so would save you the cost of heating water only to have it diverted into the cold-side pipes, to be cooled then re-heated again; not to mention the cost of wasting hot water when you want cold water on the cold side. Find out whether you will need a mixing valve near the HW tank.
I'm partial to the loops with a third line for a hot return. Leave the cold alone.
Thanks for the reply. Hadn't thought about the cold now being hot. I don't think that a third line is an option (cost factor).
How about an inline heat coil on the hot line...is there such a thing???
There are on-demand water heaters, installed in-line near the fixture.
There are the tankless or on demand heaters. Don't know if there is a common one just to boost the temp for a couple of minutes. Most of them take large amounts of gas or electricity becuase they are expected to heat cold water to hot, on the run.You can also get 5 to 10 gallon point of use electric water heaters.They are basically scaled down version of a regular electric WH including the need for a safety release valve. But because of their small size and the storage tank they don't take as much power at any one time. Some of them run off of 120.
"Note that the UP15 pump is rated for up to 3.5' of head, so it won't work well for a second floor bathroom"
Just a little technical clarification here. The pressure difference between the HW supply and the CW supply, is not affected by elevation.
Thanks. I'm not sure I follow this line of reasoning.
Are you saying that the pump does not have to work harder to push water up to a second floor, because the water supplies (C & H) would be a closed pressurized loop, as per the original poster's initial scenario?
Could you give me more detail/explanations?
In ANY closed loop, whether we are talking about hydronic heating or domestic hotwater recirculation, elevation of various parts of the loop do not affect the pumping head required to move fluid through that loop. The exception being during system fill.
The force of gravity acting on the mass of water going "up" is matched, exactly, by the force of gravity on the mass of water goin "down".
If you were to install a pump between any points in a closed system the elevation is not a relevant part of the head equation. This would be true if you recirculated water between the basement and the second floor or between two pipes in the same room.
Though it's been a long time since I took Fluid Dynamics, I believe you're forgeting about friction/drag. Friction increases the power required to "raise" the water, but it also reduces your power gains as the water "falls", so that you don't break even. This is a VERY minimal factor, of course.Mark
friction is a factor of length and diameter of pipe, number of fittings and number and type of turns, velocity of the water, but not the head.
Woops! I guess I'm glad my line of work has nothing to do w/ what I (supposedly) studied! Sorry about that.Mark
By installing a 3-n-1 RedyTemp Optimizer on the second floor, head pressure becomes a null factor. It's easier to move water over a hill when you don't have to push or pull the water up the hill, as the water pressure would have that task, the pump would only have to do the little energy it takes to crest the peak of the hill, because the pump would be located at the top of the hill.
Hope that makes sense.
"By installing a 3-n-1 RedyTemp Optimizer on the second floor, head pressure becomes a null factor. It's easier to move water over a hill when you don't have to push or pull the water up the hill, as the water pressure would have that task, the pump would only have to do the little energy it takes to crest the peak of the hill, because the pump would be located at the top of the hill. "It doesn't matter.It is a closed loop. If you look at the static head pressure any place in the system it is zero.The only head pressure that you have is dynamic and it is the same no matter where you put the pump.
Thanks - makes sense now.
I'd stay away from a recirc. pump because of the long-term energy costs. You're creating something like a steam system. Heating water in a tank is wasteful anyway; adding all the hot water lines (and the attendant heat losses) is really wasteful.
You can put tankless, on-demand heaters at a couple of locations, and that will solve the problem. Actually, if you size the tankless units right, you can get rid of the tank heater altoegther. Major savings possible.
Have a look at http://www.seisco.com
Edited 5/8/2005 1:56 pm ET by SteelBuddha
Allow me to quibble...I agree that having a recirc system by itself is quite wasteful. That is, it makes little sense to have hot pipes in the house, while the structure is being cooled in the summertime, for example.On the other hand, water wastage is a real problem in many areas, and with a little bit of extra work, recirculation can make a lot of sense. For example, it's trivial to foam the DWV and water pipes in their joist bays with icynene not only to reduce BTU losses but to also inhibit condensation, noise, etc. Just some scrim on the backside gives the Icynene all it needs to adhere properly when installed in a interior wall.In my house, the recirc will be programmed to run during certain times of the day, such as the morning and the evening. At other times, some water will be lost while waiting for the stream to warm up. With 1-2" of insulation around most water pipes, I'd like to think that the losses will be slow...For that matter, if your aim is to really reduce water consumption BTU losses, may I suggest a GFX technology heat exchanger? Simply install one downstream from showers, pipe the cold water for the shower through the thing, and instantly reduce your hot water consumption by something like 40% or more. Naturally, bigger whole-house models can also be adopted to preheat cold water destined for the water heater.
The Taco or Metlund system is a little better than the Grundfos system if you don't mind pushing a button a few seconds before you need hot water. It doesn't need the third (recirc) pipe, and no hot water enters the cold line.
http://www.gothotwater.com/
Here's from your link: "Now you can have hot water in 15-30 seconds (depending on the size of the home and water system) without wasting a single drop and by using only a fraction of a penny's worth of electricity."15-30 seconds?!?!?! Hardly seems worth an investment to get just that result. I like the immediate results of the third line.
Well, for you impatient types, Metlund offers a motion detector. So, the pump starts as soon as someone enters the bathroom. You'll have instant hot water before you get your PJ's off. If you sleep naked, this isn't the system for you.
Also, if you let your cats have the run of the house, the pump might have a lot of false starts.
I also feel that with this system, you save the cost of pipe insulation. Even with great insulation, all the pipes will be cold in the morning. That means that the heat you're trying to save is still lost to the house, just slower.
This might be of interest http://nibco.com/cms.do?id=2&pId=200 I am considering getting one for my kitchen sink. I have seen them at Menards for around $60.00.
RU
That Nibco model requires a separate return line, which tentmaker said he couldn't do.
Thanks for the reply. Hadn't thought about the cold now being hot. I don't think that a third line is an option (cost factor).
How about an inline heat coil on the hot line...is there such a thing???
I believe they thought that a third line would not be feesable. Compare the cost of a Nibco Just Right and a return line to a remote on demand water heater plus installation. If they have multiple needs.
I guess we need to know more about their application and the structure that it is intended for.
RU
You can get small, 5 and 10 gallon, point of use electric water heaters.
Some of the suggestions sound too complicated and costly.
The Grundfos is a good system. If the lines are insulated, the energy loss is not going to be that bad. Plus, the Grundfos has a timer and a thermostat to further reduce heatloss. The power used to run the pump is insignificant, since it runs very infrequently. This system will save water, potentially a lot of water.
The dedicated return line is a better design though. One way to retrofit is to run a PEX return line, supported by the supply line.
Take a look at:
chilipepperapp.com
$179 the others units shown are very expensive in comparison, and I don't see where they do anything better.
Pete
There is a great deal of difference between the different models on the market. The Chilipepper is priced so low because it's extremely noisy (simply search the internet for chilipepper+noise) and requires that the homeowner press a button. This is not very feasible when you need hot water in a different room from where the chilipepper is installed. You also make no mention that the chilipepper consumes 3-5 amps of electric and has a limited run time.
Differences between the different models on the market are great. From simple installs to installs which require draining water heaters, shutting off the gas and even some which require shutting off the main water line.
Some require that the pump be installed on to the water heater like the Grundfos Comfort Series, then a thermo bypass valve be installed under the farthest sink from the water heater. The problem with these systems is that the valve only closes when 95 F degree water contacts the comfort valve / bypass valve. The inefficiency occurs each time cold water is used in the home "and" the water in "the hot water line is not hot", water bleeds through the bypass valve and mixes with the cold water in the cold water line. Fluctuating pressure differences during cold water usage also assist with the bleed through of water through the bypass valve. When water bleeds through the bypass valve from the hot water line "very cold city water" must fill the water heater to replace that which bled through. Additionally, since these valves don't close until 95 F degree water reaches them, when homeowners try to get cold water, they must run the cold water long enough for all the tepid water to empty / bleed through the valve until the 95F water reaches the valve and closes it, only then will they get "cold" water from their cold water faucet. Anyone who knows plumbing is aware of the problems and discomforts which occur when hot and cold water lines are open to each other taking away from the benefits of stable water pressures in a home.
I suggest you check out the following links, do some more research and judge for yourself.
http://www.redytemp.com/Hot_Water_Circulation_Systems/Hot-Water-Recirculation-System-Comparison.htm
http://www.redytemp.com/comfort_valve_vs_outlet_installl.htm