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Recirculating pump: A great water and energy saver

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Tim_Toad_HLB

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The ideas keep flowing so I wanted to share some info about this device that I installed on our hot water heater just before we opened five years ago.
Our home's footprint is a essentially a 35' x 140' rectangle and the mechanical room where the radiant heat boiler, hot water heater, electrical panel, etc. are is on one end of the house. From that point to our kitchen and one guest room is over 100'
Its a recirculating pump that goes on the outlet pipe from your hot water heater and the one I put in is designed to save the average family of four over 10,000 gallons of water and the equivilent energy needed to heat that much in a year.
It took about an hour to install and because our well is metered, we have to track our water usage because our immediate area is embroiled in the longest running water rights legal disputes in the U.S.
We have to be careful with our water to a point. Guests aren't expected to skimp in any way on bathing or comfort and thats mainly because of the measures we take internally to guarantee we have lots of good quality water at their fingertips.
This device is so cool and nobody knows its even on except that during the peak showering hours that we've determined to be from 6-10am and 6-10pm, when you open a faucet and turn it to hot, or start a shower, you get hot water in 10-15 seconds even at the outlets furthest from the hot water heater. The bathrooms closer to the meachanical room get it even quicker.
It has timer on it for programming peak times or you can have it on 24/7 which probably isn't necessary and would seem to be counterintuitive to the whole idea.
 

swirt

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/ I'm missing something here in the explanation. The pump goes on the outlet to the hotwater tank and then connects to where else? I'm guessing it connects the last hotwater line in the chain back to the source so that it can keep the hot water flowing in a loop so the water in the line is always hot (during the times that its on). Am I picturing that right?
 

Proud Texan

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How does this save water or energy? You're going to use the same amount of water whether its recirculated or not. I don't see how recirculating the water will save energy. It might give you instant hot water in a shower some distance away from the water heater. But, unless you have come across the perfect insulation for your pipes, there will be radiant heat loss in the pipes. There's also the energy required to run the pump.
Another option is to use of small tankless water heater at the point of use.
 

swirt

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How does this save water or energy? You're going to use the same amount of water whether its recirculated or not. I don't see how recirculating the water will save energy. It might give you instant hot water in a shower some distance away from the water heater. But, unless you have come across the perfect insulation for your pipes, there will be radiant heat loss in the pipes. There's also the energy required to run the pump.
Another option is to use of small tankless water heater at the point of use..
I can see how it would save water as there would be no "cold" water going down the drain waiting for the hot to arrive.
I think you are right though on the energy aspect....the radiant and conductive heat loss would be pretty large. There would be some benefit to not having to heat the entire slug of water that went down the drain waiting for the hot to arrive, but it seems like that would be small in comparison to what is lost in the pipes .... though actually with the long run of pipe that Tim described it may make sense... a 100' slug of cold water in 1/2" pipe amounts to a little over a gallon of water. ..probably close to two gallons by the time the hot really feels hot.
Of course if the return loop also went through a solar collector of some kind (given his location) it could be a real boost to the system.
 

swirt

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I did a little more reading on it. Is this the one you have? It sounds like it feeds the hot water back through the cold water pipe?? Am I following that right?
 

Tim_Toad_HLB

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/ I'm missing something here in the explanation. The pump goes on the outlet to the hotwater tank and then connects to where else? I'm guessing it connects the last hotwater line in the chain back to the source so that it can keep the hot water flowing in a loop so the water in the line is always hot (during the times that its on). Am I picturing that right?.
I'm still at a loss for exactly how it works other than the simple explanation that its like a turbocharger on your hot water heater. When it senses an open faucet, it is pushing hot water so much harder and faster than your normal water pressure that you get hot water to the demand very quickly.
So yes, you're cutting the time of water running that is going down the drain before its hot and the correpsonding energy needed by the hot water heater to "replace" the hot water lost in transport and down the drain.
This is the brand I bought and if needed for this discussion, I'll go jot down the model number.
http://www.grundfos.com/web/homeus.nsf/Webopslag/D6600B14F5C7C73386256AE9005326AE
With the "average" American using nearly 70 gallons per day, most of which is for showering and bathing, I can see where it starts adding up to some savings.
 

Proud Texan

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/ I'm missing something here in the explanation. The pump goes on the outlet to the hotwater tank and then connects to where else? I'm guessing it connects the last hotwater line in the chain back to the source so that it can keep the hot water flowing in a loop so the water in the line is always hot (during the times that its on). Am I picturing that right?.
I'm still at a loss for exactly how it works other than the simple explanation that its like a turbocharger on your hot water heater. When it senses an open faucet, it is pushing hot water so much harder and faster than your normal water pressure that you get hot water to the demand very quickly.
So yes, you're cutting the time of water running that is going down the drain before its hot and the correpsonding energy needed by the hot water heater to "replace" the hot water lost in transport and down the drain.
This is the brand I bought and if needed for this discussion, I'll go jot down the model number.
http://www.grundfos.com/web/homeus.nsf/Webopslag/D6600B14F5C7C73386256AE9005326AE
With the "average" American using nearly 70 gallons per day, most of which is for showering and bathing, I can see where it starts adding up to some savings.
.
Tim_Toad_HLB said:
So yes, you're cutting the time of water running that is going down the drain before its hot and the correpsonding energy needed by the hot water heater to "replace" the hot water lost in transport and down the drain.
It's only pushing the cold water in the line out faster so that you get hot water sooner. The volume of water in the pipe remains constant, so there's no savings there.
 

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