Hot water recirculation

Assumptions: 

Assuming that an average household consists of 3 persons in average water waste a year is estimated to be 16.425 liters equals 66 bathtubs and 37 hours waiting a year 

  1. Number of times a person is waiting a day for water to get hot at a faucet is estimated to be 5 https://energysavingtrust.org.uk/sites/default/files/reports/AtHomewithWater(7).pdf  
  2. Number of liters wasted each time at a faucet is estimated to be 2 liters, with a faucet having a flow of 6 liters per minute https://sustainabilityinfo.com/water/how-much-water-does-a-faucet-use/  
  3. Number of times a person is waiting a day for water to get hot in a shower is estimated to be 1 https://energysavingtrust.org.uk/sites/default/files/reports/AtHomewithWater(7).pdf  
  4. Number of listers wasted in the shower each time is estimated to be 5 liters with a shower head having a flow of 15 liters per minute https://sustainabilityinfo.com/water/how-much-water-does-a-faucet-use/  
  5. According to the research organisation PRB the average number of people living in a household in Europe is 2,4. Rounded up this gives an average of 3 persons per household.
    https://www.prb.org/international/indicator/hh-size-av/map/country/
  6. Waiting time for hot water is estimated to be 20 seconds each time.  
  7. Length of the pipe from the water source/heater to the faucet and shower head is estimated to 20 meters 
  8. The bathtub size is estimated at 250 liters
    https://www.badeloftusa.com/ideas/how-much-does-bathtub-hold/

 

Sources: 

Energy Saving Trust (2013) "Water at home - The biggest ever review of domestic water use in Great Britain"
https://energysavingtrust.org.uk/sites/default/files/reports/AtHomewithWater(7).pdf (1, 3) 

Sustainability Info (2021) "How much Water does a Faucet Use
https://sustainabilityinfo.com/water/how-much-water-does-a-faucet-use/ (2, 4) 

PRB (2020) PRB’s World Population Data Sheet "Average household size" 
https://www.prb.org/international/indicator/hh-size-av/map/country/ (5)

Badeloft (2021) "How Many Gallons Does a Bathtub Hold?"
https://www.badeloftusa.com/ideas/how-much-does-bathtub-hold/ (8) 

 

Estimated savings:  

Replacing a UPS 6m, speed III with a new HWR pump from Grundfos 

Old UPS 6m - speed III - Watt use: 90W - Time running a day: 24 hours* - Watt use a day: 90W 

New COMFORT BASIC - Watt use: 7W - Time running a day: 24 hours* - Watt use a day: 7W - Savings: 92% 

New COMFORT DT - Watt use: 7W - Time running a day: 10,5 hours** - Watt use a day: 3W - Savings: 97% 

New COMFORT AUTOADAPT - Watt use: 7W - Time running a day: 2,5 hours - Watt use a day: 0,7W - Savings: 99% 

New ALPHA N 25-60 180  - speed II - Watt use: 28W - Time running a day: 24 hours* - Watt use a day: 28W - Savings: 69% 

New UPS N 20-60-180 - speed II - Watt use: 70W - Time running a day: 24 hours* - Watt use a day: 70W - Savings: 22% 

* With no external timer installed 

** COMFORT DIGITAL TIMER has a factory default setting where 21 enabled 30 minutes time slots are activated 

 

Supporting facts: 

Eco Friendly Habits (2021) "Water Waste Facts: Stats About Water Consumption & Usage"
https://www.ecofriendlyhabits.com/water-wasting-facts/  

Energy Efficiency Standards Group, Energy Analysis and Environmental Impacts Division (2011) "Water and Energy Wasted During Residential Shower Events: Findings from a Pilot Field Study of Hot Water Distribution Systems"
https://energyanalysis.lbl.gov/publications/water-and-energy-wasted-during

Energy Efficiency Standards Group, Energy Analysis and Environmental Impacts Division (2011) "Water and Energy Wasted During Residential Shower Events: Findings from a Pilot Field Study of Hot Water Distribution Systems"
https://eta-publications.lbl.gov/sites/default/files/water_and_energy_wasted_during_residential_shower_events_findings_from_a_pilot_field_study_of_hot_water_distribution_systems_lbnl-5115e.pdf