According to BS9251:2021 (Fire sprinkler systems for domestic and residential occupancies — Code of practice) a Priority Demand Valve is a “valve for isolating the supply to the domestic service in the event of sprinkler operation” (BS9251:2021 3.22), and according to paragraph 5.11.3.2 such a device is required where the available flow rate does not exceed 25lpm (for Cat 1 systems) or 50lpm (for Cat 2/3/4 systems); in addition, such valves should always close on loss of power.
In terms of the valves themselves, there are very few requirements within the BS9251 standard (i.e. they should close on sprinkler activation, and they should close on loss of power), as this is a design standard rather than a product standard. When we are asked, “Can I have a PDV but I don’t want it normally closed”, then it’s not a Priority Demand Valve, it’s just a valve which closes on demand – which is perfect for some applications, but it is not compliant with BS9251:2021.
It’s important to recognise that fact the BS9251 is a design standard – effectively, it highlights the design, workings and components to be used on certain types of fire sprinkler systems in order to be compliant. As such, when customers ask, “Does such-and-such a product comply to the standard XYZ?”, the answer is often, “It will help you comply with the standard, if it’s designed in, installed and operated properly, but any product cannot comply with any standard by itself.”
At SEP, we have designed and offer several different solutions to your PDV needs. ALL of our valves close on loss of power as standard, they are all controlled by a 24VDC circuit for safety, and come complete with a compact ‘plug and play’ control panel where all you need to do is connect your fire sprinkler flow switch (or other NC circuit which opens on fire sprinkler activation). All of our valves are also WRAS-approved for peace of mind and compliance with local water bylaws.
- For pipe sizes over 2”/50mm, we have an actuated butterfly valve. This valve has a battery back-up for assured operation. Other benefits are: a manual override (which should be used only in certain conditions), visible position indicator, LED status indicators, and open/closed monitoring which can be connected to a fire panel.
- For pipe sizes up to 2”/50mm, we offer two options:
- Solenoid Valve: simpler, smaller and less expensive than the ball valve, they have a higher 16 bar pressure rating, and they close instantaneously; however, they need a small (0.3 bar) positive pressure to open so they may not be suitable for tank-fed applications; also, there is no visual open/closed indicator and no manual override (although BS9251 states that a small-bore bypass may be installed).
- Actuated Ball Valve: compared to the solenoid valve, the ball valves need no positive pressure to open (can be used on tank-fed systems) and are not permanently powered open; in addition, they have a visual position indicator and encompass a manual override. Conversely, they are a little more expensive and larger, and the pressure rating is 10 bar; although the close time is a little longer, it’s still only around 10 seconds at most.
For more information have a look at our Priority Demand Valves datasheet and for more details our Priority Demand Valves O&M manual – and, of course, contact us any time for a quotation and lead time.