HTM 01-05 says dental water lines should be flushed for at least two minutes at the beginning and end of the day, and after any significant period when they have not been used, such as a lunch break. They should also be flushed for at least 20 to 30 seconds between patients.
Those timings come from paragraph 6.85 of HTM 01-05, the decontamination guidance for dental practices in England. Always check them against the manufacturer’s instructions for your dental chair.
The flushing routine at a glance
| When | Flush for at least |
|---|---|
| Start of the day | 2 minutes |
| End of the day | 2 minutes |
| After a significant period of non-use, such as lunch | 2 minutes |
| Between patients | 20 to 30 seconds |
HTM 01-05 adds that care should be taken to minimise splashing and aerosol formation.
Why flushing alone is not enough
HTM 01-05 is candid about the limits. It says these flushing routines have only a small effect on biofilm build-up, but that they usefully reduce microbiological counts in the water delivery tube while patients are likely to be exposed. It also says no currently available single method or device will completely eliminate contamination, so a combination of methods is needed.
CQC’s mythbuster on waterlines explains why contamination builds up: there is a source of nutrients, the plastic tubing contains plasticisers, surgery temperatures can warm the water, and water can sit stagnant overnight and at weekends. It says you must control legionella within the dental waterline system, though no single treatment is completely effective.
Your routine therefore usually has three parts: flushing, disinfecting and draining.
Disinfecting dental water lines
HTM 01-05 says disinfection should be carried out periodically, and that the manufacturer’s instructions should be consulted in all cases. It gives no single interval for every practice, so the manufacturer’s instructions and your written waterline scheme decide how often. HSE’s HSG274 Part 2 lists draining, cleaning, flushing and disinfecting dental equipment twice daily, typically at the start and finish of each working day. Ask your competent person how this fits with HTM 01-05 and your chair manufacturer’s instructions.
Not every product suits every chair. HTM 01-05 says the agents it mentions should only be used where recommended by manufacturers, and that lines should be thoroughly flushed after disinfection and before being returned to clinical use. CQC adds that staff should review the instructions for the dental chair unit, as some manufacturers do not recommend specific products.
Dental water lines shock treatment
People often ask about “shock” treatment of waterlines. The word does not appear in HTM 01-05, and CQC’s mythbuster does not use it either. The guidance talks about periodic disinfection instead. If someone recommends a shock dose, check that the product and the dose are covered by your dental chair manufacturer’s instructions, and ask your competent person how it fits your scheme.
Where there is visual contamination, HTM 01-05 says flushing with a suitable disinfectant followed by thorough washing is necessary. For self-contained water bottles, it says that if contamination is routinely detected, the interval between flushing operations will need to be decreased.
End-of-day draining and water bottles
HTM 01-05 says at-risk systems, particularly those used with the patient, should be drained down at least at the end of each working day. Where manufacturers provide protocols for daily cleaning, those should be applied.
Self-contained water bottles should be removed, flushed with distilled or reverse osmosis water, left open to the air to dry overnight, and stored inverted.
Dental water lines testing
Routine laboratory testing is generally not expected. CQC says that apart from situations where there are taste or odour problems, it is not necessary to carry out routine microbiological monitoring for total viable counts in dental waterlines.
Testing the water for legionella, and checking its temperature, is a separate question. CQC says how often you do that depends on your system, its components and the outcome of your risk assessment. See our article on the legionella risk assessment.
If a surgery closes for a while
Follow the manufacturer’s guidance on taking waterlines out of use. Where there isn’t any, HTM 01-05 gives a fallback:
- During a temporary closure, flush, drain and leave the lines disconnected. If that isn’t practicable, flush them weekly.
- Before bringing them back into use, flush for at least three minutes, disinfect with a suitable disinfectant, then flush for a further three minutes.
- Treat any in-line filters with a cleansing solution recommended by the manufacturer after first flushing, and replace disposable filters.
As part of bringing equipment back into use, anti-retraction valves should be checked by the responsible person. CQC lists anti-retraction valves on water and air lines among its mandatory requirements.
What an inspector will want to see
CQC says all premises are required to have a written waterline management scheme and a legionella risk assessment, and that the registered manager must implement their recommendations. In practical terms, staff should know the routine and you should have a record that it is happening. Our waterlines check and HTM 01-05 guide show how it fits with your other decontamination work.
Compliance UK runs recurring checks for the practice, each surgery and each piece of equipment, on a default schedule that you can change. Scanning an equipment QR label opens a one-screen log on a phone.
Sources
- NHS England: HTM 01-05, decontamination in primary care dental practices
- CQC: Dental mythbuster 5, legionella and dental waterline management
Sources checked on 10 November 2026.