Earth Notes: On 16WW Mains Inlet Water Temperature

Updated 2020-03-15 12:00 GMT.
Domestic mains water temperature data for 16WW on tap; seasonal min/max about 10C/20C in winter/summer. #dataset #domestic #water #temperature #CSV #MIDI
measuring mains water temperature at kitchen sink with N84FR


What is the domestic water mains temperature range seen at this suburban London kitchen tap?

Typically between about 10°C and 20°C (winter vs summer). Extremes of 6°C (2010-01-09) and 25°C (eg 2018-07-26) have been observed between 2008 and 2019 inclusive.

Is this a highly scientific study?

No. The probe is not calibrated, but the results are fairly consistent and plausible.

Water Temperature Samples

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 dishwashers ("wet white goods"), for example. Available in CSV and MIDI (sonified) formats.

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.


This data is licensed under CC0, ie effectively public domain. If you make use of this data, attribution is welcome but not obligatory.


measuring mains water temperature at kitchen sink with N84FR

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 at least 20s is allowed until the temperature reading settles. The value is then recorded in the table below.

The measuring device is a Maplin N84FR digital probe thermometer (uncalibrated) from 2008-08-30. K-type thermocouple. Range -20°C--1000°C. (Note battery (2xSR44) changed 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 some extra and missing samples.

Outside temperatures are taken from inspection of live measurements in the shaded porch near the kitchen, and/or from local weather reports.


16WW Water Mains Inlet Temperature
16WW Domestic Water Mains Inlet Temperature, approximately noon mid-month, at kitchen tap, Kingston-upon-Thames, London, KT1 3JA, UK
water, main, temperature, sample, domestic
date created
date published
date modified
temporal coverage
spatial coverage
UK centre 51.406696N,-0.288789E elevation 16m
canonical URL
this descriptive text with markup
HTML table
CSV as date,temperature
even-cadence (monthly) data CSV as temperature
even-cadence (monthly) MIDI audio
this dataset is licensed under CC0, ie it is effectively public domain; if you make use of this data, attribution is nice but not obligatory


Code to extract data from this HTML file can be found at script/

Basically a small sed script extracts the data lines from the HTML and converts them to a more simple CSV format for other tools to process. The CSV consists of the date (ISO 8601 format, no time) in the first column, and the recorded temperature in integer Celsius in the second. (Rows with decimals would be dropped.)

A sample output line is:


Some months have multiple readings. (Some have no readings.) To make some subsequent processing easier, the script script/ discards all but the first reading for each month.

There are other similar scripts available.


A simple audification/sonification via plain-text data file and MIDI for temperatures from 2008 up to 2019-10:

"water temperature" Uploaded . Duration 33 seconds. Download MP3 clip 307kB (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 128kB, hi-fi FLAC clip 1187kB.

(See more (including harps!) over at Water Music: How Does Tap-water Temperature Sound in Time-lapse?)

Here are 'live' auto-generated even-cadence CSV and MIDI files from all data:

The alternative data formats are auto-built with these tools:

script/16WW-mains-water-inlet-temperature-toCSV < .source.HTML > data/16WW-mains-water-inlet-temperature.csv
script/mkaudio/fill-in-months-CSV < data/16WW-mains-water-inlet-temperature.csv > data/16WW-mains-water-inlet-temperature-month-cadence.csv
script/mkaudio/texttoMIDI0 data/16WW-mains-water-inlet-temperature-month-cadence.csv > data/16WW-mains-water-inlet-temperature-month-cadence.mid

Data Points

Mains water inlet temperatures at 16WW (KT1 3JA)
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 UTCBBC:
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.
12°C2018-12-15 15:08 UTC~3°C outside.
11°C2018-12-29 10:02 UTC~10°C outside. (Reading mainly on 12°C, but flickering to 11°C as captured in the photo!)
10°C2019-01-15 11:52 UTC~8°C outside.
9°C2019-02-19 11:45 UTC~9°C outside.
11°C2019-03-16 12:02 UTC~12°C outside.
12°C2019-04-15 10:30 UTC~12°C outside.
15°C2019-05-14 12:00 UTC~18°C outside.
17°C2019-06-15 11:16 UTC~19°C outside.
21°C2019-07-15 08:15 UTC~17°C outside.
22°C2019-08-10 17:00 UTC~20°C outside.
21°C2019-08-14 13:30 UTC~16°C outside.
20°C2019-09-09 10:00 UTC~14°C outside.
21°C2019-09-15 11:58 UTC~20°C outside.
17°C2019-10-14 12:30 UTC~13°C outside.
15°C2019-11-03 14:57 UTC~11°C outside.
12°C2019-11-15 11:58 UTC~7°C outside.
11°C2019-12-05 20:14 UTC~9°C outside.
11°C2019-12-15 11:55 UTC~9°C outside.
11°C2020-01-12 10:53 UTC~11°C outside.
11°C2020-01-19 18:20 UTC~2°C outside.
10°C2020-01-26 18:15 UTC~9°C outside.
10°C2020-01-31 12:50 UTC~12°C outside. Reading briefly flickering down to 9°C.
11°C2020-02-15 12:05 UTC~13°C outside. Reading initially flickering down to 10°C.
10°C2020-02-29 12:45 UTC~7°C outside. Readings between 9 and 11°C.
12°C2020-03-15 11:58 UTC~11°C outside. Readings between 13 and 11°C.