Earth Notes: On 16WW Mains Inlet Water Temperature

Domestic mains water temperature data for 16WW on tap; seasonal trends are clear, with min/max about 10/20C winter/summer.


This is a data set of regular samples of domestic mains water infeed temperatures in suburban London (UK), useful for estimating required temperature 'lift' and therefore energy demand for DHW (domestic hot water), washing machines and dishwashersu ("wet white goods"), for example.

The HTML table below is laid out to be easy to parse with text processing tools, eg to convert into CSV or load into a speadsheet, if required.


Water temperature is measured at the 16WW kitchen tap (which is close to the water main feed to the property) running a fast-flowing stream.

The probe tip is placed up inside the tap nozzle with the tip not touching anything if possible.

Typically upwards of 20s is allowed until the temperature reading settles before the value is recorded in the table below.

The measuring device is a Maplin N84FR digital probe thermometer from 2008/08/30. "K-type thermocouple." "Range -20°C--1000°C." (Note battery changed: 2xSR44, 2015/09/15. Again 2018/08/14.)

The aim is to measure near (solar) noon where possible, and near the middle of each calendar month to be representative for that month. There are extra and missing samples though.


This page is marked up with JSON-LD microdata to describe the data set.

Data Points

19°C2008/08/30 11:00 UTC approx
14°C2008/11/19 08:36 UTC
10°C2008/12/03 19:00 UTC
17°C2009/06/02 10:00 UTC
20°C2009/06/27 20:47 UTC
20°C2009/08/30 11:00 UTC
16°C2009/10/22 12:25 UTC
11°C2009/12/07 10:00 UTC
10°C2009/12/15 12:00 UTC
6°C2010/01/09 21:12 UTC
8°C2010/01/20 07:38 UTC
10°C2010/04/03 10:38 UTC
13°C2010/04/25 15:00 UTC
15°C2010/05/23 11:00 UTC
19°C2010/06/26 11:46 UTC
21°C2010/07/17 10:00 UTC
19°C2010/09/12 16:15 UTC
15°C2010/10/18 11:03 UTC
15°C2010/11/06 16:40 UTC
11°C2010/11/28 19:00 UTC
9°C2010/12/03 08:42 UTC
8°C2010/12/20 10:10 UTC
The temperature of water going to homes from reservoirs in the Thames Valley and London has dipped to a record low, officials have revealed. Thames Water said due to freezing weather water had cooled to a "staggeringly chilly" 1.8C. Until now the coldest water temperature recorded was 4.9C in 2001 - the average is 7.3C.
8°C2011/01/01 17:26 UTC
9°C2011/02/14 10:25 UTC
11°C2011/03/28 08:37 UTC
12°C2011/04/09 17:15 UTC
17°C2011/05/27 20:07 UTC
18°C2011/06/21 16:30 UTC
20°C2011/07/04 09:08 UTC
20°C2011/08/13 10:10 UTC
19°C2011/09/10 12:00 UTC
15°C2011/10/23 16:25 UTC
15°C2011/11/09 22:00 UTC
13°C2011/11/27 14:30 UTC
10°C2011/12/12 14:20 UTC
10°C2011/12/28 10:25 UTC
11°C2012/01/15 13:20 UTCTemperature higher than previous even though outside temperatures have been much closer to freezing for several days.
10°C2012/02/01 19:30 UTCOutside temperatures again around freezing for several days.
9°C2012/02/08 09:00 UTCOutside temperatures again around freezing for several days.
12°C2012/04/09 08:15 UTC
18°C2012/05/28 06:06 UTC
19°C2012/06/30 18:23 UTC
19°C2012/07/09 09:30 UTC
22°C2012/08/19 15:00 UTCMeasurement taken by Ellie; alternating between 21 and 22.
16°C2012/10/08 06:26 UTC
15°C2012/10/14 16:12 UTC
14°C2012/10/28 18:20 UTC
13°C2012/11/15 18:53 UTC
11°C2012/11/30 12:00 UTCReading alternating between 11 and 12. Outside below freezing overnight.
9°C2012/12/15 08:45 UTC
10°C2012/12/31 12:00 UTC~11°C outside.
10°C2013/01/06 18:13 UTC~8°C outside.
10°C2013/01/15 12:15 UTC~2°C outside.
8°C2013/02/15 11:52 UTC~8°C outside and sunny.
9°C2013/03/15 11:53 UTC~7°C outside.
9°C2013/04/05 17:42 UTC~7°C outside; has been a very cold March.
10°C2013/04/15 11:00 UTC~14°C outside.
14°C2013/05/15 13:00 UTC~11°C outside.
16°C2013/06/15 16:00 UTC~16°C outside.
21°C2013/07/15 13:15 UTC~27°C outside.
22°C2013/08/11 08:50 UTC~17°C outside.
18°C2013/09/15 11:05 UTC~13°C outside.
16°C2013/10/17 12:34 UTC~16°C outside.
10°C2013/11/15 18:53 UTC~7°C outside.
11°C2013/12/08 09:52 UTC~7°C outside.
11°C2013/12/15 11:47 UTC~11°C outside.
12°C2014/01/15 21:25 UTC~10°C outside.
9°C2014/02/15 12:00 UTC~10°C outside.
11°C2014/03/15 09:40 UTC~10°C outside.
14°C2014/04/14 12:00 UTC~14°C outside.
16°C2014/05/17 17:30 UTC~22°C outside (BBC KT1 Weather; 23°C external sensor).
20°C2014/07/14 11:50 UTC~20°C outside (BBC KT1 Weather).
21°C2014/08/15 10:53 UTC~16°C outside (BBC KT1 Weather; 16.5°C external sensor).
20°C2014/09/15 08:52 UTC~15°C outside (BBC KT1 Weather; 15.5°C external sensor).
17°C2014/10/14 12:30 UTC~13°C outside.
14°C2014/11/15 11:52 UTC~10.5°C outside.
12°C2014/12/15 12:00 UTC~7°C outside.
10°C2014/12/30 12:00 UTC~0°C outside.
11°C2015/01/15 12:00 UTCReading flickering to 10°C briefly. ~8°C outside.
9°C2015/02/15 11:15 UTC~7°C outside.
10°C2015/03/15 11:54 UTC~6.5°C outside.
13°C2015/04/15 06:30 UTC~12°C outside.
16°C2015/05/15 11:05 UTC~14°C outside.
17°C2015/06/15 11:05 UTC~16°C outside.
21°C2015/07/13 11:00 UTC~19°C outside.
20°C2015/08/01 17:40 UTC~20°C outside.
21°C2015/08/21 11:00 UTC~22.5°C outside.
18°C2015/09/15 11:00 UTC~14°C outside; probe needs new battery and reading was wandering somewhat...
15°C2015/10/15 11:00 UTC~11°C outside
15°C2015/11/15 11:50 UTC~15°C outside
13°C2015/12/15 12:10 UTC~11°C outside
11°C2016/01/15 12:30 UTC~4°C outside
10°C2016/02/14 16:15 UTC~5°C outside
10°C2016/03/14 10:00 UTC~7.5°C outside
12°C2016/04/15 10:30 UTC~13°C outside
16°C2016/05/15 11:00 UTC~16°C outside
18°C2016/06/13 11:00 UTC~17°C outside
21°C2016/07/15 08:10 UTC~16°C outside
20°C2016/08/15 11:00 UTC~21°C outside
21°C2016/09/16 08:00 UTC~17°C outside
16°C2016/10/15 10:48 UTC~12°C outside
13°C2016/11/15 12:00 UTC~14°C outside
12°C2016/12/15 12:05 UTC~10°C outside
9°C2017/01/15 12:02 UTC~3°C outside
13°C2017/03/14 14:18 UTC~13°C outside
15°C2017/04/15 11:00 UTC~13°C outside
16°C2017/05/15 10:50 UTC~15°C outside
21°C2017/06/15 10:57 UTC~26°C outside
22°C2017/07/15 11:22 UTC~19°C outside
21°C2017/08/13 13:22 UTC~22°C outside
21°C2017/08/15 10:58 UTC~20°C outside
18°C2017/09/15 11:01 UTC~14°C outside
18°C2017/10/15 11:00 UTCReading flickered to 17°C briefly. ~16°C outside as measured by porch sensor, though BBC Weather for KT1 claims 18°C.
14°C2017/11/16 07:20 UTC~10°C outside
10°C2017/12/16 12:02 UTC~4°C outside
10°C2017/12/31 09:30 UTC~11°C outside
11°C2018/01/15 18:30 UTC~8°C outside; display flickering between 11 and 12.
9°C2018/02/15 23:50 UTC~5°C outside.
9°C2018/03/15 12:00 UTC~11°C outside.
13°C2018/04/15 11:00 UTC~13°C outside.
17°C2018/05/13 12:05 UTC~15°C outside.
16°C2018/05/15 10:58 UTC~21°C outside.
20°C2018/06/15 11:00 UTC~22°C outside.
24°C2018/07/13 17:04 UTC~24°C outside.
25°C2018/07/15 10:58 UTC~28°C outside.
25°C2018/07/26 12:01 UTC~32°C outside.
24°C2018/08/02 12:29 UTC~28°C outside.
24°C2018/08/14 11:21 UTC~22°C outside. (Battery low.)
23°C2018/08/15 10:50 UTC~22°C outside. Reading flickering to 22°C.
20°C2018/09/15 10:56 UTC~17°C outside.
19°C2018/09/23 12:35 UTC~11°C outside.
18°C2018/10/15 10:56 UTC~14°C outside.
14°C2018/11/14 08:40 UTC~11°C outside.
14°C2018/11/15 12:00 UTC~14°C outside.