Backflow prevention in a dental or medical practice
A clinical practice is a high hazard connection to the town water main. That single classification sets the device, the space it needs and an annual testing obligation.
The short answer
Backflow prevention is the least glamorous line in a clinical fitout and one of the few that carries an obligation continuing for as long as you occupy the building. It is also routinely discovered after the hydraulic design is finished, which is the expensive moment.
Key points
- A dental or medical practice is generally a high hazard connection, whatever its size.
- High hazard means a reduced pressure zone device, not a lesser valve.
- An RPZ discharges water when it operates, so it needs a location with a drain.
- It must be registered with your water authority and tested annually by an accredited tester.
Backflow prevention is the least glamorous line in a clinical fitout and one of the few that carries an obligation continuing for as long as you occupy the building. It is also routinely discovered after the hydraulic design is finished, which is the expensive moment.
What backflow is, in one paragraph
Water in a main normally flows one way. If pressure drops, through a burst, a fire event or heavy draw-off nearby, it can reverse, and whatever is connected downstream can be drawn back into the drinking water supply. Backflow prevention stops that happening, and the level of protection required depends on how bad the consequence would be.
Why a practice is high hazard
Hazard is rated low, medium or high according to what could come back. A clinical practice generally sits at high hazard, and the reason is the equipment rather than the size of the business.
A dental chair connects the water supply to handpieces and a cuspidor, with aspiration close by, which is a direct connection to contaminated water. Medical practices carry their own versions: sterilisers, treatment equipment, sluice and slop hoppers. A single-chair suburban practice attracts the same classification as a much larger facility, because the classification follows the nature of the connection rather than the volume.
High hazard means a reduced pressure zone device, commonly called an RPZ or RPZD. It is the highest level of protection and it is not interchangeable with the lesser devices used on lower hazard connections.
What that means for the fitout
An RPZ device is a physical object with requirements that have to be designed in rather than found room for later.
- It discharges water when it operates. The relief valve dumps to atmosphere, so it needs a tundish or drain and a location where discharging water does not damage anything. This is the requirement most often missed.
- It needs access for testing. Annually, by a person with test equipment. Behind a fixed joinery panel is not access.
- It is not small. Allow for the device, isolation valves and clearance around it.
- It causes pressure loss. Which the hydraulic design has to account for, or the far end of the tenancy suffers.
- It cannot be in a pit that floods, or anywhere it can be submerged.
There is also a choice about where protection sits. Containment protection at the property boundary protects the water main from the whole site. Zone or individual protection sits further in, protecting parts of the building from each other. A tenancy in a multi-tenanted building may find containment already exists at the boundary and still need its own protection for the practice, which is a question for the hydraulic consultant and the water authority rather than an assumption.
The obligation that does not end
Once installed, the device has to be registered with your water authority, commissioned, and tested annually by an accredited tester, with results submitted. This is a continuing compliance obligation attached to the property and to you as the occupier.
It is inexpensive and it is forgotten constantly. It surfaces in two places: when a water authority audits, and during a lease assignment or the sale of a practice, when somebody asks for four years of test records that were never kept. Put it on the same annual calendar as your other statutory items the day you open.
Where to raise it
At hydraulic design, before the plan is fixed. The device needs a location with a drain, access and clearance, and those three together are difficult to retrofit into a tenancy that has been laid out around rooms.
It is also worth asking about during due diligence. In an existing tenancy that was previously a practice there may be a compliant device already, correctly located, which is a genuine advantage. In one that was a shop, there will not be.
Sources and further reading
AS/NZS 2845 covers backflow prevention devices and their testing, and AS/NZS 3500 covers plumbing and drainage. Hazard rating and the protection required on a specific connection are determined by your hydraulic consultant and your water authority.
Source for AS/NZS 4815 and 4187 reprocessing, AS 1428.1 access and AS 1668.2 ventilation. The standards themselves are purchased, not free.
Practice guidance for Australian dentists, including infection prevention and control.
The National Construction Code: building classification, fire separation, egress, sanitary provisions and access.
Questions
Does a dental practice need backflow prevention?
Generally yes, and at the high hazard level. A dental chair connects the water supply to handpieces and a cuspidor with aspiration nearby, which is a direct connection to contaminated water. The classification follows the nature of the connection rather than the size of the practice, so a single-chair clinic attracts the same requirement as a large facility.
What is an RPZ valve?
A reduced pressure zone device, the highest level of backflow protection, required on high hazard connections such as clinical practices. It is not interchangeable with the lesser devices used on low and medium hazard connections, and it relieves water to atmosphere when it operates, so it needs a drain.
Where does the backflow device go?
Somewhere with a tundish or drain for its relief discharge, physical access for annual testing, clearance around the device and valves, and no risk of submersion. Those requirements together are hard to retrofit, which is why it belongs in the hydraulic design rather than being found a home once the rooms are laid out.
How often does backflow prevention need testing?
Annually, by an accredited tester, with results submitted to your water authority. The device also has to be registered when installed. It is a small recurring cost that is routinely forgotten, and it surfaces during audits and at the sale or assignment of a practice when several years of records are requested.
Who is responsible, the landlord or the tenant?
It depends on where the protection sits and what your lease says. Containment protection at the property boundary is often the owner's, while protection specific to your practice is generally yours as the occupier. Establish it in writing rather than assuming, because the annual testing obligation follows whoever holds it.
Send us the floor plan
A site assessment tells you what the tenancy can take and what it will cost to get there, ideally before you have signed for it.