Potable Water in a Dental Setting

In a UK dental practice, the requirements for potable water are stringent and primarily guided by Health Technical Memorandum 01-05 (HTM 01-05): Decontamination in primary care dental practices, along with other relevant health and safety legislation like the Health and Safety at Work etc Act 1974 and Approved Code of Practice (ACOP) L8 for the control of Legionella bacteria.

Here’s a breakdown of key aspects:

General Potable Water Use:

• For general use (sinks, toilets, staff facilities), mains potable water is acceptable and subject to general water safety regulations, including Legionella risk assessments. One must be aware that the quality of the city water can be affected by several outside factors such as the age of the metal piping and certainly by roadworks or building work being carried out near to the site. A constant update to the log book will highlight any changes to the quality of the city water.
• Cold water systems should be kept below 20°C and hot water above 45°C to inhibit bacterial growth, particularly Legionella.
• A Legionella risk assessment is mandatory for all dental practices to identify and manage risks associated with water systems. This includes having a written scheme of control and regular monitoring.

Dental Unit Water Lines (DUWLs):

This is the most critical area for water quality in a dental practice. While mains potable water can be used to supply DUWLs, it is strongly recommended and widely practiced to use reverse osmosis (RO) water or distilled water in self-contained dental chair systems.

HTM 01-05 states that the water used in DUWLs must comply with drinking water standards, with a bacterial level not exceeding 100-200 Colony Forming Units (CFU)/ml of aerobic heterotrophs at 22°C.

Maintenance of DUWLs:

• Flushing: DUWLs should be flushed for at least 2 minutes at the beginning and end of the day, and for 20-30 seconds between patients.
• Disinfection: Regular disinfection of DUWLs (at least weekly, or as per manufacturer’s instructions) is crucial to prevent biofilm build-up.e.g Peroxy Ag+
• Water Bottles (Self-contained systems):
• Should be removed, flushed with distilled or RO water, and left open to air for drying overnight, stored inverted.* With Peroxy Ag+ ,based on thorough testing ,evaluation and compliance the bottles can be left attached to the dental unit.This may apply to other disinfectant systems. With Peroxy Ag+ being used as a disinfectant we recommend the bottles are removed cleaned and sanitised and inverted at the weekend or prior to an extended shut down.
• Should be filled with freshly produced (less than 12 hours old) RO or distilled water at the start of each day.
• Should not be filled with tap water.
• Anti-retraction valves: Water and air lines must have anti-retraction valves fitted to
  prevent backflow and contamination.

Autoclaves (Steam Sterilisers):

HTM 01-05 states that autoclaves should be filled, at least daily, using distilled or RO water. This is essential to prevent scale build-up and ensure effective sterilisation of instruments.

Instrument Cleaning (Ultrasonic Cleaners/Manual Cleaning):

Instruments cleaned in an ultrasonic cleaner or by hand should be rinsed thoroughly in a dedicated sink or bowl using satisfactory potable water, or freshly prepared RO water or distilled water to remove residual soil and detergents.

Key takeaway for UK dental practices:

While mains potable water is used for general facilities, specialised dental equipment like DUWLs and autoclaves require purified water (preferably RO or distilled) to meet infection control standards and minimise the risk of patient and staff exposure to waterborne pathogens. Strict adherence to HTM 01-05 and regular risk assessments and maintenance are paramount.

Dental Decontamination Limited’s role in providing Potable water.

May we establish what consumables are involved in a reverse osmosis system:

• Sediment filter. Usually one of these is fitted. Don’t rule out having two, but fitted in parallel. Lifespan 6-12 months depending on location and usage.
• Carbon filters. 1-2 fitted. Lifespan 6-12 months.
• Dental unit Membrane. Rated from 50 gallons per day (gpd) and 400 gpd.
• Optional DDL TAC scale reducer available with a 2-3 year lifespan

The reverse osmosis system will convert the city water down to between 3 and 25 ppm tds depending on the location and the quality of the city water. That r.o water is then “polished” in a de ioniser pod to reduce the tds right down to ZERO.

DDL’s attention to improving the systems:

Over many years Dental Decontamination Limited have studied compliant potable water introducing many innovative equipment and sanitisation protocols.

We have discovered that every site has to be analysed on an individual basis.

Many things have to be considered whilst working towards producing suitable potable water:

• Geography of the site to determine the ppm tds of the city water. The CO2 content of the
  water can effect the quality and should be checked with the water board provider.
• Number of dental units.
• Number of autoclaves and type… for instance certain S type autoclaves have an upper limit of 3 ppm tds (this can be expressed in micro siemens).
• Space available to accommodate a system.
• Services available.

Once the above information is collected we can analyse it and then make recommendations on what system should be introduced.

We will also introduce systems and technology to minimise the service intervals but maintain the low ppm tds.

We recommend that in hard water areas a DDL TAC system is fitted to reduce the scale in the incoming city water.

A DDL WS1 will ensure the practice has no or very few failed dip slides that are taken from the reverse osmosis tap.

When we conducted our tests of tanked systems we discovered that because the protective chlorine had been removed from the city water they were susceptible to infections.

• We discovered that the following areas of the system had consistent infections:
• The entrance area of the reverse osmosis tank.
• The de -ioniser pods housing the de ioniser cartridges.
• The pipe leading to the reverse osmosis tap.

The common denominator?… the r.o water has no protection …protection city water possesses.

We initially used 3% Hydrogen Peroxide to sanitise the systems internal surfaces which took place during the service protocol. Method statement available.

The results were encouraging and were documented. Every time we carry out a service of a reverse osmosis system we sanitise all the surfaces with 3% H202. With 3% H202 not being a chemical it breaks down into H and O molecules POST ACTION.

Nigel Bannister
Dental Decontamination Limited
www.DentalDecontamination.co.uk

June 2025