TW postcode district map, Sunbury-on-Thames
Supplier statuses last checked .
The TW postcode area covers 21 districts and 11,122 live postcodes, from TW1 to TW98. It is centred on Sunbury-on-Thames and also covers Ashford, Staines-upon-Thames, Egham and Walton-on-Thames.
Districts here average 530 postcodes.
Where the TW districts sit
1 district is plotted without a label where labels would overlap; every one is in the table below.
Where TW sits
It falls across Greater London, Surrey and Windsor and Maidenhead.
Water supply across TW
All 21 TW districts are supplied by Thames Water. That makes TW simple in a way many areas are not: one company, one set of rules, one status to check.
Thames Water has a hosepipe ban in force from 23 July 2026, covering the whole of TW.
The shape of the TW area
TW3 is the largest district with 787 postcodes around Sunbury-on-Thames, and TW98 the smallest with 58. The area divides into 80 postcode sectors.
The numbering is not continuous. TW runs up to 98 but has only 21 districts, so 77 numbers are unused:.
Several districts share a settlement, which is a common source of confusion when a form rejects an address: TW1, TW2, TW3, TW4, TW5, TW7, TW8, TW9, TW10, TW11, TW12, TW13 and TW16 all point at Sunbury-on-Thames, TW6, TW14 and TW15 all point at Ashford and TW18 and TW19 all point at Staines-upon-Thames.
TW98 is a non-geographic district: it carries no coordinates because it is used for PO boxes and large users rather than for streets. It appears in the table below but cannot be placed on the map.
What borders TW
TW sits next to UB (Ashford) to the north, KT (Esher) to the south, W (London) to the north east, SW (City of Westminster) to the east and HA (Bushey) to the north.
Its neighbours run in 4 different directions, so TW is landlocked by other postcode areas on most sides.
TW districts, settlements and water supply
| District | Principal settlement | Water company | Hosepipe ban status |
|---|---|---|---|
| TW1 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW2 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW3 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW4 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW5 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW6 | Ashford | Thames Water | Ban in force |
| TW7 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW8 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW9 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW10 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW11 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW12 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW13 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW14 | Ashford | Thames Water | Ban in force |
| TW15 | Ashford | Thames Water | Ban in force |
| TW16 | Sunbury-on-Thames | Thames Water | Ban in force |
| TW17 | Walton-on-Thames | Thames Water | Ban in force |
| TW18 | Staines-upon-Thames | Thames Water | Ban in force |
| TW19 | Staines-upon-Thames | Thames Water | Ban in force |
| TW20 | Egham | Thames Water | Ban in force |
| TW98 | — | Thames Water | Ban in force |
Principal settlement is the town or city each district sits in or nearest to, derived from OS Open Names. It is not the Royal Mail post town, which is licensed data and not published openly. Status is resolved live from each company’s own notice.
Water hardness in TW
No water company covering TW publishes hardness figures as open data. The gap is named per district below so you know who to ask.
| District | Hardness | As published | Supply zone | Published by |
|---|---|---|---|---|
| TW1 | Not published by Thames Water. Check with your supplier. | |||
| TW2 | Not published by Thames Water. Check with your supplier. | |||
| TW3 | Not published by Thames Water. Check with your supplier. | |||
| TW4 | Not published by Thames Water. Check with your supplier. | |||
| TW5 | Not published by Thames Water. Check with your supplier. | |||
| TW6 | Not published by Thames Water. Check with your supplier. | |||
| TW7 | Not published by Thames Water. Check with your supplier. | |||
| TW8 | Not published by Thames Water. Check with your supplier. | |||
| TW9 | Not published by Thames Water. Check with your supplier. | |||
| TW10 | Not published by Thames Water. Check with your supplier. | |||
| TW11 | Not published by Thames Water. Check with your supplier. | |||
| TW12 | Not published by Thames Water. Check with your supplier. | |||
| TW13 | Not published by Thames Water. Check with your supplier. | |||
| TW14 | Not published by Thames Water. Check with your supplier. | |||
| TW15 | Not published by Thames Water. Check with your supplier. | |||
| TW16 | Not published by Thames Water. Check with your supplier. | |||
| TW17 | Not published by Thames Water. Check with your supplier. | |||
| TW18 | Not published by Thames Water. Check with your supplier. | |||
| TW19 | Not published by Thames Water. Check with your supplier. | |||
| TW20 | Not published by Thames Water. Check with your supplier. | |||
| TW98 | Not published by Thames Water. Check with your supplier. | |||
Hardness is published per census area, not per postcode, so these figures characterise a district rather than measuring one address. They are a scale and taste matter, not a safety one. Hardness data version wessex-water@2022-2025+yorkshire-water@2026.
Download the TW data
No signup, no email wall. GeoJSON carries the district points, the supplier and the live status, so it can be dropped straight into a map.
District positions are averaged postcode centroids from OS Code-Point Open. They show roughly where a district sits, not where its boundary runs, and are not legal boundaries.
Frequently asked questions
How many postcode districts are in the TW area?
There are 21 TW postcode districts, running from TW1 to TW98, and they contain 11,122 live postcodes across 80 sectors.
What towns does the TW postcode area cover?
TW covers Sunbury-on-Thames, Ashford, Staines-upon-Thames, Egham and Walton-on-Thames. The area takes its name from Sunbury-on-Thames, and each district is listed with its settlement in the table on this page.
Which water company supplies TW postcodes?
Thames Water supplies all 21 TW districts. Supply boundaries follow the pipe network rather than postcode geography, so confirm against your water bill if you are near the edge of the area.
Why do TW1 and TW2 both say Sunbury-on-Thames?
TW1, TW2, TW3, TW4, TW5, TW7, TW8, TW9, TW10, TW11, TW12, TW13 and TW16 all serve Sunbury-on-Thames, covering different parts of it. A single town routinely needs more than one postcode district once it passes a few thousand delivery points, so this is normal rather than an error in an address.
What is TW98 used for?
TW98 is a non-geographic postcode district. It is used for PO boxes and large users such as banks and government departments that receive enough mail to need their own code, so it has no streets and no position on a map.
Can I download a free TW postcode map?
Yes. This page offers the TW districts as GeoJSON, CSV and SVG, free and with no signup or email address required. The GeoJSON carries each district's position, its water company and its current restriction status, so it can be dropped straight into a mapping tool.
Which councils cover the TW postcode area?
TW reaches into Greater London, Surrey and Windsor and Maidenhead. A postcode area is not a council area: they were drawn for different purposes and a single district can sit across a council boundary, so your postcode does not tell you which authority you pay.