What's Really in Your Tap Water? A Friendly Guide to Fluoride and Your Postcode

Ask a room full of people about fluoride and you will get a fascinating mix of confidence, confusion and the odd strong opinion. The truth is that UK tap water is not one national recipe. Some areas have naturally higher levels of fluoride, some have water fluoridation schemes, and plenty have low levels. As we head through 2026, your postcode can be a useful starting point, but it is not a crystal ball.

What fluoride actually does

Fluoride helps enamel resist acid attacks and can help repair early damage before a cavity forms. For most people, the main source is fluoride toothpaste, not water. Water fluoridation is a background measure: it tops up the level in the supply for everyone in that area, whether they think about it or not. Toothpaste is the bit you control twice a day.

Why postcodes differ

Water comes from local rivers, reservoirs and boreholes, and the minerals in it vary. Some water companies add fluoride to bring levels up to a target, usually around 1 milligram per litre, which is often written as 1 ppm. Naturally occurring fluoride can also be present without any scheme. The UK has fluoridation schemes in parts of England, and some areas have naturally fluoridated water. Scotland, Wales and Northern Ireland have different arrangements, so it is worth checking rather than assuming.

How to check your area

Start with your water supplier's website. Most have a postcode lookup and publish an annual water quality report. If you are on a private supply, such as a borehole, ask for a water test. Your dentist or health visitor may also know about local guidance, especially for children. Do not rely on a neighbour's memory or a social media post from another county. Water supplies can change, and the report for your supplier is the best place to look.

What the number means for you

Levels are usually given in milligrams per litre. A level around 1 mg/l is the target for fluoridation schemes. Much of the UK sits below that. A high natural level is possible but uncommon, and your supplier can advise if you are worried. The important thing is not to treat a postcode as a diagnosis. It is one piece of information, along with your diet, your brushing habits, your medicines and your dental history.

For children

Children's toothpaste is where the detail really matters. UK guidance generally suggests a smear of toothpaste with around 1000 ppm for children under three, and a pea-sized amount of 1350 to 1500 ppm for children aged three to six. From age seven, most children can use 1350 to 1500 ppm. In areas with fluoridated water, a dentist or health visitor may suggest a lower-fluoride toothpaste for young children. Ask rather than guess. Children should not eat toothpaste, and mouthwash is not usually recommended for young children unless a dentist advises it.

For adults

Most adults do well with a toothpaste containing 1350 to 1500 ppm fluoride, used twice a day. Spit after brushing rather than rinsing with water, because rinsing washes away the fluoride you have just applied. If you are at higher risk of decay, your dentist may prescribe a higher-strength toothpaste, such as 2800 ppm or 5000 ppm. Mouthwash can be useful at a separate time of day, but it is not a substitute for brushing. If you use a water filter, check what it removes. Many jug filters do not remove fluoride, while reverse osmosis can. Do not spend money on a filter assuming it will change your fluoride intake unless you have checked.

The debate, fairly

The argument about water fluoridation is not new. Supporters point to evidence that it reduces tooth decay, especially in children, and that it can help people who do not get regular dental care. Critics raise concerns about consent, mass medication, mild dental fluorosis and whether the benefits are as strong when fluoride toothpaste is widely available. Mild fluorosis can appear as faint white marks on teeth and is usually cosmetic. UK schemes are monitored, and the level used is controlled. It is reasonable to have questions. It is less reasonable to let fear or certainty do all the talking.

Buying guide: what to look for

Toothpaste: check the ppm on the tube. Adults and most children over seven should look for 1350 to 1500 ppm unless a dentist says otherwise. Children under three usually need about 1000 ppm. Mouthwash: choose alcohol-free and fluoride-containing if you use one, and do not give it to young children without advice. Filters: check the manufacturer's claims and your water supplier's report before buying. Supplements: fluoride supplements are not a casual purchase; they should only be used on professional advice.

Questions worth asking

What is the fluoride level in my water supply? Does my child need a different toothpaste strength? Do we need supplements, or would that be too much? Should I use a fluoride mouthwash, and when? Does my water filter remove fluoride? Am I at higher risk of decay because of medication, dry mouth, braces or a previous cavity? These questions turn a vague worry into a useful conversation.

The bottom line

Your postcode is a starting point, not the whole story. Brush twice a day with the right strength of fluoride toothpaste, spit rather than rinse, keep sugary snacks to mealtimes, and see your dentist regularly. If you are unsure what your local water means for your family, ask. At Battle Road Dental, we are happy to talk through fluoride, toothpaste strengths and the practical bits that actually make a difference.