Thread: Water Heater circulation pumps

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The video promotes hot water circulation pumps as environmentally friendly and cost effective. Installation cost of about $1000. Their reason is that you waste several gallons of water waiting for it to get hot.

One thing they did not address is heat loss in the plumbing 24 hours a day causing the water heater to fire more often. Installation cost aside it seems to me that the energy cost would be much more expensive than the water cost. (how about installing an instant water heater instead)


I would appreciate your opinion on this.

Bruce

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Bruce, the instant water heater only heats when the water is turned on through coils the water loss before you get water to the fixture is the same. A circulating pump keeps the hot water at the fixtures at all times and when installed under the slab keeps the floor warm in the winter. The pipes in the sand and all pipes insulated well the heater does not run anymore than normal. I have had one for 15 years, and changed out the pump once.

If you have the funds get a thermal camera.

Originally Posted by mathew stouffer

If you have the funds get a thermal camera.

Matthew,

I'm quite stumped by your reply ...

How on earth does that relate as an answer to the question posted.

Originally Posted by Bruce Thomas

it seems to me that the energy cost would be much more expensive than the water cost.

Bruce,

It's not "just the water cost".

You also must calculate in the cost to heat all that wasted water, which was once heated, and the cost to re-heat all the wasted water which will now cool in the lines.

Overall, energy-wise, I would think it would be a toss up. Giving this a value of +/-0.

Overall, water conservation-wise, it's a no brainer - install the recirculating pump. Giving this a value of +1.

End result of +1. I.e., you gain more than you lose, and, right now, there are many large areas of the southeast where water is really, really, really, important.

Jerry,

I'll give you the South West and other water short areas like Los Vegas but my point is the heat loss in the circulation system 24 hours a day.

Without the pump you have several gallons of wasted water and the related sewage cost but I'm thinking once the water cools in the pipes over night the water heater is much better suited to keeping it warm for morning than circulating continuously. Then there is the cost of running the pump.

I'm thinking most people take 1 shower per day, teenagers excepted, then there is laundry, cooking and dishes. Heaviest use in the morning for showers, laundry can be any time etc.

I guess the question is how much heat is lost through the pipes in your home (every home is different) in a given day? Rhetorical question.

We have a water heater expert speaking at our chapter meeting next week, I'll also see what he thinks and let you know.

Thanks,
Bruce

These circulation pumps are great, especially for medium to larger homes.

Get one with a timer and just run it in the mornings and around dinner cleanup time.

They save water, energy and time.

A return line is used for new construction which is best but if the house is finished you will need modifications or just get the circulator pump that installs under a sink. This method pushes the water back in the cold line. You will lose your cold water while it is running with this retrofit method.

The closed loop method that uses the return line will need check valves and a thermal expansion tank.

Don't solder pipes onto the pump until you disassemble the pump or the heat can damage the internal parts.

I have a few under sink 2.5 gallon heaters that are nice when the circulator is not running. If you have a large family, just leave the circulator pump on 24/7.

Originally Posted by Bruce King

These circulation pumps are great, especially for medium to larger homes.

Get one with a timer and just run it in the mornings and around dinner cleanup time.

Isn't it needed the least at busy times? If someone else has just used the hot water, then you don't have wait around for it anyway. The time you waste a bunch of water is when no one has used it for a while and the water in the pipe has cooled off.

I recommend a timer and a thermostat for the circulating pumps. There is also a newer valve that I was interested in looking at for my house for this purpose. From what I read, you turn on the hot water at your shower, and nothing at all comes out of the valve until the water is warm. It sends the water back down the cold line until the set temperature is reached. You don't need a dedicated return line with this type of system, although I think the valves are pretty expensive. I haven't seen one in an inspection yet.

If you do install a pump you might opt to install it either over the existing auxiliary pan or put a separate pan below it. The can and often do leak. A dedicated circuit would be nice as well with a disconnect switch at the unit.

Aaron

Originally Posted by John Arnold

Isn't it needed the least at busy times? If someone else has just used the hot water, then you don't have wait around for it anyway. The time you waste a bunch of water is when no one has used it for a while and the water in the pipe has cooled off.

I know what you mean but it just don't work that way, hot water turns luke warm real quick even in insulated pipes. The water savings is a good thing but most people have these for the luxury of having almost instant hot water.
If you have more than 3 people in the house, just let it run 24/7.

Its not really instant hot water, the loop may only run to within 4-10 feet of the fixture so a small wait is still going to occur.

Another thing to remember with the timer is that if you want 2-3 showers starting at 6am and the pump timer kicks in at 5:55am, the water heater gets a lot of cold water dumped into in while it empties the return line into the heater. So the timer needs to be set for 5:30 or 5:40 am to allow for recovery and full use of the tank.

I also have another water heater in series with the main one, it has a 220V switch and stays off unless we have company. It serves as a storage tank mostly and gains some heat from the garage in the summer. Well water is very cold and expensive to heat.

They save water, energy and time.

Bruce, I will concede the saving water and time.
But a circulator pump will not save any energy, there will be an increased energy use when you factor in the cost of running the pump.
But the larger energy cost will be the loss of heat in the lines which could be quite substantial. There is no way that the cost of water will ever give a ROI for a circulator system.
They are a great convenience, but not a money saver unless you are paying LOTS for your water and very little for your energy.

Some homes will have a cost savings depending on many variables. Many factors apply making monitoring/calculations near impossible but....

Anyone who has closely watched an outdoor spa heat up after draining and refilling knows this: The time it takes to heat water from 60 to 80 is much longer than from 80 to 100. I have monitored this many times even on a 6kw electric spa, it is way longer.

Taking this knowledge and applying it to a water heater is very much the same. You let that tank get that extra cold water sent in while you are waiting for it to reach the fixture and the time to heat it goes up. Is it more than the heat loss from the circulator pipes? Hard to prove either way.

I could put a timer on my water heater and see how much it runs and then check again without the pump in use but other variables might change such as the number of showers and the temperature of the water coming in from the 80 foot pipe under the garage slab and driveway slab. Could be an interesting experiment.

While you have standby losses from the hot pipes, even if insulated, the "loss" is into the thermal envelope of the home, which helps heat the home, so it isn't a total loss. Without a circ., you have to run the hot water for 30 seconds or more to get really hot water. That means wasting a few gallons of water. Also, as the water leaves the tank, cold water refills it and sooner or later, it will fire, thus using more energy. No free ride. If a tank has a circ. pump and fires as water is drawn off, it doesn't have to fire as much to maintain temp. on a gallon or two whereas it will fire much longer when a larger chunk of the tank is drawn off. Here, I'm speaking of a boiler with an indirect tank, which is much more efficient holding heat (1/4 of one degree per hr.)

I spoke with the Buderus rep. about my new boiler and he swears the energy loss is negligible with a recirc. as long as you insulate the pipes.

Bob

Originally Posted by Bob Harper

Without a circ., you have to run the hot water for 30 seconds or more to get really hot water.

Bob,

I've had many homes where that "30 seconds or more" was "more" ... as in "more like 5 minutes", some even "more like 15 minutes" - not guessing, timed it with my watch.

That's A LOT of water, and wasted heat to heat that water, and waster heat to re-heat the replacement water.

the energy loss is negligible with a recirc. as long as you insulate the pipes.

Yep. Same here.

Anyone who has closely watched an outdoor spa heat up after draining and refilling knows this: The time it takes to heat water from 60 to 80 is much longer than from 80 to 100. I have monitored this many times even on a 6kw electric spa, it is way longer.

I don't think a BTU know's how hot the water is when the water is being heated. If you place 16 ounces of water at 59°F into a stovetop pan and turned on the gas burner, it would take one BTU to raise the temperature of the water to 60°F. As more BTUs continue to flow from the gas flame, the water will eventually reach the boiling point of 212°F.

Physics does support that idea, but remember, the heating element is immersed in the cold water of spa's and water heater's therefore causing the heating elements performance to diminish. The stove burner is not affected as much by the load that is not engulfing the source.

I have observed this slow heating of cold/cooler water in spa's for years after draining and refilling, have owned a few over the last 18 years. One was a 240V 6kw heater and the other is 120V 1.5kw heater, they both do the same thing and it is not just a little difference, its major. The only reason I can think of is the cold water effect on the immersed element.

I don't want to get too technical (we need a thermodynamics professor here) but a BTU is a BTU and a calorie is a calorie. Considering that the water chemistry is the same, it takes the same amount of energy to raise a given amount of water at the same pressure 1 degree.

Here is what I am curious about. What is the actual cost of a circulation pump.

Installation cost around $1000.00.
Timed operation cost of the pump
Heat loss in the pipe both supply and return as opposed to without a pump having a slug or cold water entering the heater while waiting for hot water to get to the fixture and them cooling off after use.

I'm thinking it may be much more cost and energy efficient to plump the home with only 1 cold line and have a small on demand unit for each area of use in a new build only of course. It would be a much higher install cost but over the long run of 20 years I'm thinking it would be a great savings but I don't know how much.

What's your opinion?

Bruce

I say say we call ..........................................." Mythbusters"

Originally Posted by Bruce Thomas

Installation cost of about $1000.

The video also mentions installation at time of "new construction". Could be done on existing, but a bit more challenging and 'spensive.

Recirc pumps have been standard here for years in apt buildings of course. Some developers started putting them into larger SF homes a few years ago. The trend died quickly. I'm sorry guys but I've always thought a recirc pump in an SF is a dumb idea and waste of money.
An idea (too long in coming) that has gained popularity is to separate out the water use areas and install multiple hot water units. Such as one tank(less) for each floor or one tank(less) for master bath another for kitchen and other baths etc.
I know having 2-3 tankless units isn't for everyone but I like it. I'm looking into upgrading to at least one solar unit later this year. Anyone tried one yet?
Have fun
Markus

Originally Posted by Bruce Thomas

I don't want to get too technical (we need a thermodynamics professor here) but a BTU is a BTU and a calorie is a calorie. Considering that the water chemistry is the same, it takes the same amount of energy to raise a given amount of water at the same pressure 1 degree.

True but heating it with gas or electric?

Originally Posted by Bruce Thomas

I Here is what I am curious about. What is the actual cost of a circulation pump.

$200-$300 plus piping costs + labor. $25 - $75 annual cost assume 24/7 operation and particular pump(need varies depending on head pressure on pump. See Grundfos comfort system for one type.

Originally Posted by Bruce Thomas

I Installation cost around $1000.00.
Timed operation cost of the pump
Heat loss in the pipe both supply and return as opposed to without a pump having a slug or cold water entering the heater while waiting for hot water to get to the fixture and them cooling off after use.

See above

Originally Posted by Bruce Thomas

I 'm thinking it may be much more cost and energy efficient to plump the home with only 1 cold line and have a small on demand unit for each area of use in a new build only of course. It would be a much higher install cost but over the long run of 20 years I'm thinking it would be a great savings but I don't know how much.

Too many factors. Need a calculator and some estimations of use.

Originally Posted by Bruce Thomas

What's your opinion?

Bruce

Not sure yet, I'm working through the same issue in my home.

There is also a non electric system but I can no longer find the info.
It worked on a heat siphon method but maybe it didn't work and is no longer around.

Originally Posted by Michael Larson

There is also a non electric system but I can no longer find the info.
It worked on a heat siphon method but maybe it didn't work and is no longer around.

Good old fashioned gravity water heating system - just make sure the plumber does not install any heat traps in it.

Start off down low, run the pipe up and over, maintaining going up (either inclined or in steps) to the far end, where the pipe returns down low and goes back to the bottom of the water heater).

No energy cost (other than lost heat) as the water is gravity fed up and across the loop, cooling as it goes, which then falls back down and back to the water heater (this would be a constant, but slow, action). Probably not real efficient as a hot water circulating system, but it would work.

Thanks Jerry,

I had one of the devices in hand one day at the local Fleet Farm.
As I remember, it containd a check valve and three ports for pipe connection. I'm sure it was a gravity type system.

I found a link describing what you refer to above. LINK

Michael,

Being as we have a single story house with a huge (did I say HUGE) attic (9:12 slope roof), I've thought about installing a copper loop to the master bath at the far end, returning with it to the water heater in the garage.

Then, to create the correct difference in temperature to create the flow, I would insulate the first 40 feet or so with greater insulation than the remainder of the outward flow piping (to get the water flowing in that direction by keeping it hotter), then limiting the insulation on the first 40 feet or so of the return, with no insulation on the remaining portion to get it to cool down quicker (enhancing the flow).

However ...

Somewhere in the house (where - I have not found yet), *there must be an autocirc installed* ... or "something"?????

Because we get hot (should I say HOT) water at our master tub within a few seconds, even on a cold day!

There was a Heat Recovery Unit installed on the heat pump refrigerant line, but that was abandoned and disconnected, so "something is somewhere".

But ... there is no a hot water recirculating pump or line to/from the water heater.

Some day I will likely find *it*, whatever *it* is.

But until then, it really does not matter.

Originally Posted by Jerry Peck

Some day I will likely find *it*, whatever *it* is.

Well when you do be sure and tell us.

Thanks Bruce: every county and municipality giving building permits should insist on the installation of the circulating pump. It is easy at time of construction and the pump pachage costs about $200. We have not had to deal with water shortages , so we are not conscious of the cost - and if we do not have water. The load on the waste utilities is also a factor as it has to be treated. There are huge benefits. Danny O'Donovan. North Carolina

Originally Posted by Danny O'Donovan

Thanks Bruce: every county and municipality giving building permits should insist on the installation of the circulating pump. It is easy at time of construction and the pump pachage costs about $200. We have not had to deal with water shortages , so we are not conscious of the cost - and if we do not have water. The load on the waste utilities is also a factor as it has to be treated. There are huge benefits. Danny O'Donovan. North Carolina

Where do you draw the line Danny?

Do you want government to mandate 12" insulated stud walls, geothermal heating plants, compact fluorescent light bulbs, 62 deg. maximum temperature(80 min. in summer), etc. etc.

What ever happened to freedom.

Michael: freedom was thrown out with the bathwater years ago! Have you noticed how many new laws were passed last year alone, at Local, State and Federal level? Thousands! if we are free why new laws? These posts are probably being monitored ? In Charlotte, NC we have a Mayor who works for Duke Energy, who controls our water supply. Last May 8th, Duke said there will be a water problem before year end 2007. Three months of the highest lawn watering season went by before restrictions were introduced, on August 8th.
There is a shortfall of approximately $12million, in the water department budget. Nobody has been laid off, but guess what, the Mayor announces the need to increase water charges by 18%!
Now that is Leadership we do not need. The Mayor did NOT announce the restrictions, but he did announce the iINCREASE in charges. Guess what, he is running for Governor and touting this as prudent Leadership!
Thank you for replying to my post. I do not think Government can do anything better than the people. Danny.

Originally Posted by Danny O'Donovan

I do not think Government can do anything better than the people. Danny.

On that we agree. Let the market place determine what should be installed in home. Government intervention in housing requirements has only increased the cost to everyone in the name of helping.

I know you meant well but we have given up way too many freedoms.
It's time to start taking them back by putting people in office who believe in freedom and not government control.

Originally Posted by Michael Larson

On that we agree. Let the market place determine what should be installed in home. Government intervention in housing requirements has only increased the cost to everyone in the name of helping.

Versus unscrupulous builders who simply install/build with junk and rip off the purchaser?

There is a balance between 'free market' and 'market freedom', and, if not for the unscrupulous builders of the past, the codes of today would not be as lengthy and encompassing as they are - because builders would be doing what is needed because, well, because ... it is what is needed.

We all inspect 'new homes', think what they would be like *without* todays codes? Think back to aluminum wiring, no termite protection treatments, lack of EERO, the list could go on and on indefinitely.

FREDOM ISN'T FREE, A PRICE MUST BE PAID. That being said, and hopefully understood, as a retired Army guy and soon to be an "associate home inspector", I read these posts and garner knowledege from you all. I'd rather see some University take on this subject and do the research then post the studied results so we all can figure it out, Whatever happened to the guy in Mississippi who figured out that he could efficiently run his automobile off h2o and battery power? No new laws and no new taxes we are not enforcing what we have well. Oh well that's my 2 cents. Keep up the good works.
Bill

One can have a small tankless water heating system for a bathroom which takes away the need for a recirculating system.

Works great for us.

Noritz - The #1 Manufacturer of Tankless Gas Hot Water Heaters

rick