Thames Water Hardness: 302 ppm Lookup

About Thames Water

Thames Water is the largest water and wastewater services company in the UK, serving over 15 million customers across London and the Thames Valley. The region sits on chalk and limestone aquifers, producing notoriously hard water with high calcium carbonate levels.

At 302 ppm on average, Thames Water ranks as very hard water. See how it compares across the UK in our 50 hardest water areas ranking.

Worth reading: our water softener guide compares the options for Thames Water customers, and our limescale removal guide has quick fixes for kettles, taps, and boilers.

Areas Served by Thames Water

Every postcode district, sorted by hardness.

Postcode	Town	Hardness	PPM	Level
E7	London	350	350 ppm	Very Hard
OX13	Abingdon	350	350 ppm	Very Hard
SL3	Slough	350	350 ppm	Very Hard
E6	London	349	349 ppm	Very Hard
OX12	Wantage	349	349 ppm	Very Hard
OX44	Oxford	349	349 ppm	Very Hard
SL2	Slough	349	349 ppm	Very Hard
E5	London	348	348 ppm	Very Hard
OX11	Didcot	348	348 ppm	Very Hard
SL1	Slough	348	348 ppm	Very Hard
E4	London	347	347 ppm	Very Hard
OX10	Wallingford	347	347 ppm	Very Hard
SL0	Iver	347	347 ppm	Very Hard
E3	London	346	346 ppm	Very Hard
KT24	Leatherhead	346	346 ppm	Very Hard
N9	London	346	346 ppm	Very Hard
E2	London	345	345 ppm	Very Hard
KT23	Leatherhead	345	345 ppm	Very Hard
N8	London	345	345 ppm	Very Hard
E1	London	344	344 ppm	Very Hard
KT22	Leatherhead	344	344 ppm	Very Hard
N7	London	344	344 ppm	Very Hard
KT21	Ashtead	343	343 ppm	Very Hard
N6	London	343	343 ppm	Very Hard
EC2A	London	342	342 ppm	Very Hard
KT20	Tadworth	342	342 ppm	Very Hard
N5	London	342	342 ppm	Very Hard
N4	London	341	341 ppm	Very Hard
N3	London	340	340 ppm	Very Hard
W9	London	340	340 ppm	Very Hard
N2	London	339	339 ppm	Very Hard
RM19	Purfleet On Thames	339	339 ppm	Very Hard
W8	London	339	339 ppm	Very Hard
N1	London	338	338 ppm	Very Hard
RM18	Tilbury	338	338 ppm	Very Hard
W7	London	338	338 ppm	Very Hard
RM17	Grays	337	337 ppm	Very Hard
W6	London	337	337 ppm	Very Hard
HA9	Wembley	336	336 ppm	Very Hard
RM16	Grays	336	336 ppm	Very Hard
W5	London	336	336 ppm	Very Hard
HA8	Edgware	335	335 ppm	Very Hard
OX9	Thame	335	335 ppm	Very Hard
RM15	South Ockendon	335	335 ppm	Very Hard
W4	London	335	335 ppm	Very Hard
HA7	Stanmore	334	334 ppm	Very Hard
RM14	Upminster	334	334 ppm	Very Hard
SW1Y	London	334	334 ppm	Very Hard
W3	London	334	334 ppm	Very Hard
EC1Y	London	333	333 ppm	Very Hard
GU35	Bordon	333	333 ppm	Very Hard
HA6	Northwood	333	333 ppm	Very Hard
OX7	Chipping Norton	333	333 ppm	Very Hard
RM13	Rainham	333	333 ppm	Very Hard
SW1X	London	333	333 ppm	Very Hard
W2	London	333	333 ppm	Very Hard
GU34	Alton	332	332 ppm	Very Hard
HA5	Pinner	332	332 ppm	Very Hard
RM12	Hornchurch	332	332 ppm	Very Hard
SW1W	London	332	332 ppm	Very Hard
EC4Y	London	331	331 ppm	Very Hard
GU33	Liss	331	331 ppm	Very Hard
HA4	Ruislip	331	331 ppm	Very Hard
IG11	Barking	331	331 ppm	Very Hard
OX5	Kidlington	331	331 ppm	Very Hard
RM11	Hornchurch	331	331 ppm	Very Hard
SW1V	London	331	331 ppm	Very Hard
EC1V	London	330	330 ppm	Very Hard
GU32	Petersfield	330	330 ppm	Very Hard
HA3	Harrow	330	330 ppm	Very Hard
IG10	Loughton	330	330 ppm	Very Hard
OX4	Oxford	330	330 ppm	Very Hard
RM10	Dagenham	330	330 ppm	Very Hard
GU31	Petersfield	329	329 ppm	Very Hard
HA2	Harrow	329	329 ppm	Very Hard
OX3	Oxford	329	329 ppm	Very Hard
EC4V	London	328	328 ppm	Very Hard
GU30	Liphook	328	328 ppm	Very Hard
HA1	Harrow	328	328 ppm	Very Hard
OX2	Oxford	328	328 ppm	Very Hard
HA0	Wembley	327	327 ppm	Very Hard
OX1	Oxford	327	327 ppm	Very Hard
RG31	Reading	327	327 ppm	Very Hard
SE9	London	327	327 ppm	Very Hard
EC1R	London	326	326 ppm	Very Hard
HP9	Beaconsfield	326	326 ppm	Very Hard
RG30	Reading	326	326 ppm	Very Hard
SE28	London	326	326 ppm	Very Hard
SE8	London	326	326 ppm	Very Hard
SW20	London	326	326 ppm	Very Hard
HP8	Chalfont St Giles	325	325 ppm	Very Hard
SE27	London	325	325 ppm	Very Hard
SE7	London	325	325 ppm	Very Hard
SW1P	London	325	325 ppm	Very Hard
EC4R	London	324	324 ppm	Very Hard
HP7	Amersham	324	324 ppm	Very Hard
NW9	London	324	324 ppm	Very Hard
SE26	London	324	324 ppm	Very Hard
SE6	London	324	324 ppm	Very Hard
DA9	Greenhithe	323	323 ppm	Very Hard
HP6	Amersham	323	323 ppm	Very Hard
NW8	London	323	323 ppm	Very Hard
SE25	London	323	323 ppm	Very Hard
SE5	London	323	323 ppm	Very Hard
DA8	Erith	322	322 ppm	Very Hard
EC1N	London	322	322 ppm	Very Hard
HP5	Chesham	322	322 ppm	Very Hard
NW7	London	322	322 ppm	Very Hard
SE24	London	322	322 ppm	Very Hard
SE4	London	322	322 ppm	Very Hard
DA7	Bexleyheath	321	321 ppm	Very Hard
EC1M	London	321	321 ppm	Very Hard
HP4	Berkhamsted	321	321 ppm	Very Hard
NW6	London	321	321 ppm	Very Hard
OX39	Chinnor	321	321 ppm	Very Hard
SE23	London	321	321 ppm	Very Hard
SE3	London	321	321 ppm	Very Hard
DA6	Bexleyheath	320	320 ppm	Very Hard
EC4N	London	320	320 ppm	Very Hard
HP3	Hemel Hempstead	320	320 ppm	Very Hard
NW5	London	320	320 ppm	Very Hard
SE2	London	320	320 ppm	Very Hard
SE22	London	320	320 ppm	Very Hard
WC2R	London	320	320 ppm	Very Hard
DA5	Bexley	319	319 ppm	Very Hard
EC4M	London	319	319 ppm	Very Hard
HP2	Hemel Hempstead	319	319 ppm	Very Hard
NW4	London	319	319 ppm	Very Hard
SE1	London	319	319 ppm	Very Hard
SE21	London	319	319 ppm	Very Hard
DA4	Dartford	318	318 ppm	Very Hard
HP1	Hemel Hempstead	318	318 ppm	Very Hard
KT19	Epsom	318	318 ppm	Very Hard
NW3	London	318	318 ppm	Very Hard
SE20	London	318	318 ppm	Very Hard
DA3	Longfield	317	317 ppm	Very Hard
KT18	Epsom	317	317 ppm	Very Hard
NW2	London	317	317 ppm	Very Hard
SW1H	London	317	317 ppm	Very Hard
DA2	Dartford	316	316 ppm	Very Hard
KT17	Epsom	316	316 ppm	Very Hard
NW1	London	316	316 ppm	Very Hard
W1W	London	316	316 ppm	Very Hard
WC2N	London	316	316 ppm	Very Hard
DA1	Dartford	315	315 ppm	Very Hard
KT16	Chertsey	315	315 ppm	Very Hard
OX33	Oxford	315	315 ppm	Very Hard
SW9	London	315	315 ppm	Very Hard
KT15	Addlestone	314	314 ppm	Very Hard
RG9	Henley On Thames	314	314 ppm	Very Hard
SW1E	London	314	314 ppm	Very Hard
SW8	London	314	314 ppm	Very Hard
UB11	Uxbridge	314	314 ppm	Very Hard
W1U	London	314	314 ppm	Very Hard
KT14	West Byfleet	313	313 ppm	Very Hard
RG8	Reading	313	313 ppm	Very Hard
SW7	London	313	313 ppm	Very Hard
UB10	Uxbridge	313	313 ppm	Very Hard
W1T	London	313	313 ppm	Very Hard
KT13	Weybridge	312	312 ppm	Very Hard
RG7	Reading	312	312 ppm	Very Hard
SW6	London	312	312 ppm	Very Hard
W1S	London	312	312 ppm	Very Hard
GU9	Farnham	311	311 ppm	Very Hard
KT12	Walton On Thames	311	311 ppm	Very Hard
RG6	Reading	311	311 ppm	Very Hard
SW5	London	311	311 ppm	Very Hard
GU8	Godalming	310	310 ppm	Very Hard
IG9	Buckhurst Hill	310	310 ppm	Very Hard
KT11	Cobham	310	310 ppm	Very Hard
RG5	Reading	310	310 ppm	Very Hard
RM9	Dagenham	310	310 ppm	Very Hard
SW1A	London	310	310 ppm	Very Hard
SW4	London	310	310 ppm	Very Hard
WC2H	London	310	310 ppm	Very Hard
EC1A	London	309	309 ppm	Very Hard
GU7	Godalming	309	309 ppm	Very Hard
IG8	Woodford Green	309	309 ppm	Very Hard
KT10	Esher	309	309 ppm	Very Hard
RG4	Reading	309	309 ppm	Very Hard
RM8	Dagenham	309	309 ppm	Very Hard
SW3	London	309	309 ppm	Very Hard
E1W	London	308	308 ppm	Very Hard
GU6	Cranleigh	308	308 ppm	Very Hard
IG7	Chigwell	308	308 ppm	Very Hard
N22	London	308	308 ppm	Very Hard
RM7	Romford	308	308 ppm	Very Hard
SW2	London	308	308 ppm	Very Hard
EC4A	London	307	307 ppm	Very Hard
GU5	Guildford	307	307 ppm	Very Hard
IG6	Ilford	307	307 ppm	Very Hard
N21	London	307	307 ppm	Very Hard
RG2	Reading	307	307 ppm	Very Hard
RM6	Romford	307	307 ppm	Very Hard
TW20	Egham	307	307 ppm	Very Hard
WC2E	London	307	307 ppm	Very Hard
GU4	Guildford	306	306 ppm	Very Hard
IG5	Ilford	306	306 ppm	Very Hard
N20	London	306	306 ppm	Very Hard
RG1	Reading	306	306 ppm	Very Hard
RM5	Romford	306	306 ppm	Very Hard
GU3	Guildford	305	305 ppm	Very Hard
IG4	Ilford	305	305 ppm	Very Hard
RM4	Romford	305	305 ppm	Very Hard
GU2	Guildford	304	304 ppm	Very Hard
GU29	Midhurst	304	304 ppm	Very Hard
IG3	Ilford	304	304 ppm	Very Hard
RM3	Romford	304	304 ppm	Very Hard
W1K	London	304	304 ppm	Very Hard
WC2B	London	304	304 ppm	Very Hard
GU1	Guildford	303	303 ppm	Very Hard
GU28	Petworth	303	303 ppm	Very Hard
IG2	Ilford	303	303 ppm	Very Hard
RM2	Romford	303	303 ppm	Very Hard
W1J	London	303	303 ppm	Very Hard
WC2A	London	303	303 ppm	Very Hard
E20	Olympic Park	302	302 ppm	Very Hard
GU27	Haslemere	302	302 ppm	Very Hard
IG1	Ilford	302	302 ppm	Very Hard
RG29	Hook	302	302 ppm	Very Hard
RM1	Romford	302	302 ppm	Very Hard
SW19	London	302	302 ppm	Very Hard
GU26	Hindhead	301	301 ppm	Very Hard
RG28	Whitchurch	301	301 ppm	Very Hard
SW18	London	301	301 ppm	Very Hard
W1H	London	301	301 ppm	Very Hard
GU25	Virginia Water	300	300 ppm	Hard
RG27	Hook	300	300 ppm	Hard
SW17	London	300	300 ppm	Hard
W1G	London	300	300 ppm	Hard
GU24	Woking	299	299 ppm	Hard
RG26	Tadley	299	299 ppm	Hard
SW16	London	299	299 ppm	Hard
W1F	London	299	299 ppm	Hard
GU23	Woking	298	298 ppm	Hard
RG25	Basingstoke	298	298 ppm	Hard
SW15	London	298	298 ppm	Hard
GU22	Woking	297	297 ppm	Hard
RG24	Basingstoke	297	297 ppm	Hard
SW14	London	297	297 ppm	Hard
W1D	London	297	297 ppm	Hard
GU21	Woking	296	296 ppm	Hard
RG23	Basingstoke	296	296 ppm	Hard
SW13	London	296	296 ppm	Hard
W1C	London	296	296 ppm	Hard
EC3V	London	295	295 ppm	Hard
GU20	Windlesham	295	295 ppm	Hard
GU52	Fleet	295	295 ppm	Hard
RG22	Basingstoke	295	295 ppm	Hard
SW12	London	295	295 ppm	Hard
W1B	London	295	295 ppm	Hard
GU51	Fleet	294	294 ppm	Hard
RG21	Basingstoke	294	294 ppm	Hard
SE19	London	294	294 ppm	Hard
SW11	London	294	294 ppm	Hard
RG20	Newbury	293	293 ppm	Hard
SE18	London	293	293 ppm	Hard
SW10	London	293	293 ppm	Hard
TW9	Richmond	293	293 ppm	Hard
WC1X	London	293	293 ppm	Hard
HP27	Princes Risborough	292	292 ppm	Hard
N1C	London	292	292 ppm	Hard
SE17	London	292	292 ppm	Hard
TW8	Brentford	292	292 ppm	Hard
EC3R	London	291	291 ppm	Hard
KT9	Chessington	291	291 ppm	Hard
SE16	London	291	291 ppm	Hard
TW7	Isleworth	291	291 ppm	Hard
WC1V	London	291	291 ppm	Hard
KT8	West Molesey	290	290 ppm	Hard
SE15	London	290	290 ppm	Hard
KT7	Thames Ditton	289	289 ppm	Hard
SE14	London	289	289 ppm	Hard
TW5	Hounslow	289	289 ppm	Hard
HP23	Tring	288	288 ppm	Hard
KT6	Surbiton	288	288 ppm	Hard
NW11	London	288	288 ppm	Hard
OX29	Witney	288	288 ppm	Hard
SE13	London	288	288 ppm	Hard
TW4	Hounslow	288	288 ppm	Hard
EC3N	London	287	287 ppm	Hard
HP22	Aylesbury	287	287 ppm	Hard
KT5	Surbiton	287	287 ppm	Hard
NW10	London	287	287 ppm	Hard
OX28	Witney	287	287 ppm	Hard
SE12	London	287	287 ppm	Hard
TW3	Hounslow	287	287 ppm	Hard
WC1R	London	287	287 ppm	Hard
EC3M	London	286	286 ppm	Hard
HP21	Aylesbury	286	286 ppm	Hard
KT4	Worcester Park	286	286 ppm	Hard
OX27	Bicester	286	286 ppm	Hard
SE11	London	286	286 ppm	Hard
TW2	Twickenham	286	286 ppm	Hard
HP20	Aylesbury	285	285 ppm	Hard
KT3	New Malden	285	285 ppm	Hard
OX26	Bicester	285	285 ppm	Hard
SE10	London	285	285 ppm	Hard
TW1	Twickenham	285	285 ppm	Hard
UB9	Uxbridge	285	285 ppm	Hard
KT2	Kingston Upon Thames	284	284 ppm	Hard
OX25	Bicester	284	284 ppm	Hard
UB8	Uxbridge	284	284 ppm	Hard
KT1	Kingston Upon Thames	283	283 ppm	Hard
TW19	Staines Upon Thames	283	283 ppm	Hard
UB7	West Drayton	283	283 ppm	Hard
WC1N	London	283	283 ppm	Hard
N19	London	282	282 ppm	Hard
TW18	Staines Upon Thames	282	282 ppm	Hard
UB6	Greenford	282	282 ppm	Hard
N18	London	281	281 ppm	Hard
TW17	Shepperton	281	281 ppm	Hard
UB5	Northolt	281	281 ppm	Hard
W14	London	281	281 ppm	Hard
N17	London	280	280 ppm	Hard
TW16	Sunbury On Thames	280	280 ppm	Hard
UB4	Hayes	280	280 ppm	Hard
W13	London	280	280 ppm	Hard
N16	London	279	279 ppm	Hard
OX20	Woodstock	279	279 ppm	Hard
TW15	Ashford	279	279 ppm	Hard
UB3	Hayes	279	279 ppm	Hard
W12	London	279	279 ppm	Hard
N15	London	278	278 ppm	Hard
TW14	Feltham	278	278 ppm	Hard
UB2	Southall	278	278 ppm	Hard
W11	London	278	278 ppm	Hard
E18	London	277	277 ppm	Hard
N14	London	277	277 ppm	Hard
TW13	Feltham	277	277 ppm	Hard
UB1	Southall	277	277 ppm	Hard
W10	London	277	277 ppm	Hard
WC1H	London	277	277 ppm	Hard
E17	London	276	276 ppm	Hard
N13	London	276	276 ppm	Hard
TW12	Hampton	276	276 ppm	Hard
E16	London	275	275 ppm	Hard
N12	London	275	275 ppm	Hard
TW11	Teddington	275	275 ppm	Hard
E15	London	274	274 ppm	Hard
EC3A	London	274	274 ppm	Hard
N11	London	274	274 ppm	Hard
TW10	Richmond	274	274 ppm	Hard
WC1E	London	274	274 ppm	Hard
E14	London	273	273 ppm	Hard
N10	London	273	273 ppm	Hard
E13	London	272	272 ppm	Hard
E12	London	271	271 ppm	Hard
GU19	Bagshot	271	271 ppm	Hard
WC1B	London	271	271 ppm	Hard
E11	London	270	270 ppm	Hard
GU18	Lightwater	270	270 ppm	Hard
WC1A	London	270	270 ppm	Hard
E10	London	269	269 ppm	Hard
GU17	Camberley	269	269 ppm	Hard
RG19	Thatcham	269	269 ppm	Hard
GU16	Camberley	268	268 ppm	Hard
RG18	Thatcham	268	268 ppm	Hard
GU15	Camberley	267	267 ppm	Hard
GU47	Sandhurst	267	267 ppm	Hard
RG17	Hungerford	267	267 ppm	Hard
GU14	Farnborough	266	266 ppm	Hard
GU46	Yateley	266	266 ppm	Hard
EC2Y	London	265	265 ppm	Hard
GU12	Aldershot	264	264 ppm	Hard
RG14	Newbury	264	264 ppm	Hard
GU11	Aldershot	263	263 ppm	Hard
RG45	Crowthorne	263	263 ppm	Hard
DA18	Erith	262	262 ppm	Hard
EC2V	London	262	262 ppm	Hard
GU10	Farnham	262	262 ppm	Hard
RG12	Bracknell	262	262 ppm	Hard
RM20	Grays	262	262 ppm	Hard
DA17	Belvedere	261	261 ppm	Hard
HP19	Aylesbury	261	261 ppm	Hard
DA16	Welling	260	260 ppm	Hard
HP18	Aylesbury	260	260 ppm	Hard
RG10	Reading	260	260 ppm	Hard
RG42	Bracknell	260	260 ppm	Hard
DA15	Sidcup	259	259 ppm	Hard
HP17	Aylesbury	259	259 ppm	Hard
RG41	Wokingham	259	259 ppm	Hard
DA14	Sidcup	258	258 ppm	Hard
EC2R	London	258	258 ppm	Hard
HP16	Great Missenden	258	258 ppm	Hard
RG40	Wokingham	258	258 ppm	Hard
DA13	Gravesend	257	257 ppm	Hard
HP15	High Wycombe	257	257 ppm	Hard
DA12	Gravesend	256	256 ppm	Hard
HP14	High Wycombe	256	256 ppm	Hard
DA11	Gravesend	255	255 ppm	Hard
HP13	High Wycombe	255	255 ppm	Hard
SL9	Gerrards Cross	255	255 ppm	Hard
DA10	Swanscombe	254	254 ppm	Hard
EC2N	London	254	254 ppm	Hard
HP12	High Wycombe	254	254 ppm	Hard
OX18	Carterton	254	254 ppm	Hard
SL8	Bourne End	254	254 ppm	Hard
EC2M	London	253	253 ppm	Hard
HP11	High Wycombe	253	253 ppm	Hard
OX17	Banbury	253	253 ppm	Hard
OX49	Watlington	253	253 ppm	Hard
SL7	Marlow	253	253 ppm	Hard
HP10	High Wycombe	252	252 ppm	Hard
OX16	Banbury	252	252 ppm	Hard
SL6	Maidenhead	252	252 ppm	Hard
E9	London	251	251 ppm	Hard
OX15	Banbury	251	251 ppm	Hard
SL5	Ascot	251	251 ppm	Hard
E8	London	250	250 ppm	Hard
OX14	Abingdon	250	250 ppm	Hard
SL4	Windsor	250	250 ppm	Hard

Products for Thames Water Customers

Popular choices for households on very hard water.

Splendid Twin Tank Water Softener

From ~£400

Twin-tank electric softener sized for 1 to 7 bedroom homes. Removes limescale from pipes, boilers, and appliances and delivers continuous soft water, with metered regeneration to keep salt use low.

View on Amazon

Philips Shower Filter

From ~£30

A quick, affordable upgrade. Reduces chlorine and limescale at the showerhead, fits any standard UK shower hose in minutes. Protects skin and hair from hard water damage.

View on Amazon

Common questions about Thames Water water hardness

How do I check Thames Water hardness by postcode?

Enter your postcode in the checker on the WaterHard.uk homepage, or find your district in the table above. Thames Water serves 412 postcode districts across London & Thames Valley, ranging from 250 to 350 ppm.

Is there a Thames Water hardness checker or map?

Thames Water publishes water quality data by postcode, but it can be scattered across PDF reports. WaterHard.uk compiles it into the searchable table above so you can find your district's reading in one place.

How hard is Thames Water water in my area?

It depends on your exact postcode. Thames Water supplies range from 250 ppm to 350 ppm, averaging 302 ppm (very hard) across 412 postcode districts in London & Thames Valley. Use the table above to find your specific district.

Do I need a water softener with Thames Water?

At 302 ppm (very hard), many households on Thames Water notice limescale in kettles and showerheads within weeks. A shower filter is the cheapest first step; a whole-house softener gives the most complete protection. See our water softener guide for a full comparison.

Thames Water Hardness