[Greenbuilding] Ask Pablo: Will a "Water-Saving" Hot Water Recirculation Pump Really Save Me Money?

Steven Tjiang steve at tjiang.org
Tue May 17 09:21:23 PDT 2011


Running the recirc pumps on an as-needed basis probably doesn't consume that
much more energy since the pump power is small and you end up heating the
pipes up whether you use or not use a recirc pump.  The water savings,
however, is unlikely to offset the installation costs.

---- Steve (KZ6LSD)


On Tue, May 17, 2011 at 7:41 AM, natural building
<naturalbuilding at shaw.ca>wrote:

> Pablo's calculations do not seem to include any insulation on the hot-water
> supply lines, nor do they account for recirc pumps that have timers and
> aquastats which are available in any reasonable $200 model (Grundfos for
> instance). Set up properly, this means that the pump is not circulating
> water during the night or at low-use times of the day which would
> dramatically reduce heat-loss. He also implies that the pipes are located in
> un-conditioned space at an average of 52 degrees F. I would suggest this is
> unrealistic.
>
> That being said, his underlying argument that they use more energy than
> they save in water is probably true. But not nearly as extreme as he makes
> out IMHO.
>
> Regards,
> Steve Satow
>
> www.naturalbuildingsite.net
> naturalbuilding at shaw.ca
>
> On 2011-05-17, at 5:45 AM, Steven Tjiang wrote:
>
> Recirc pumps saves water but are an energy waste if run continuously.  Ours
> has a button that you press manually 30 seconds or so before you use your
> faucet, and goes off when the hot water reaches the faucet.  Still I doubt
> the energy savings will offset the installation cost in any realistic amount
> of time.
>
> ---- Steve (KZ6LSD)
>
>
> On Tue, May 17, 2011 at 5:41 AM, Stephen Collette <
> stephen at yourhealthyhouse.ca> wrote:
>
>> Here is a link (hopefully it's not scrubbed) on hot water recirculating
>> pumps. Seems according to Pablo, they do not add up. I have one and
>> unplugged mine as I thought (not verified, but eyeballing my electricity
>> bill and guesstimating) that it was costing too much to run. I would be
>> curious about thoughts on this idea from others, as I know we have had
>> discussions in the past on these units.
>>
>>
>> http://www.treehugger.com/files/2011/05/ask-pablo-hot-water-recirculation-pump.php
>>
>> If the link is scrubbed, please go to treehugger . com and search ask
>> pablo - hot water recirculating pumps, and you should find it hopefully. or
>> drop this on the end of it. /
>> files/2011/05/ask-pablo-hot-water-recirculation-pump.php<http://www.treehugger.com/files/2011/05/ask-pablo-hot-water-recirculation-pump.php>
>>
>> Cheers
>>
>> Stephen
>>
>>    Stephen Collette BBEC, LEED AP, BSSO
>> *Your Healthy House* - Indoor Environmental Testing & Building Consulting
>> http://www.yourhealthyhouse.ca
>> stephen at yourhealthyhouse.ca
>> 705.652.5159
>>
>>
>>
>>
>>
>>
>>
>>
>>
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