Replacement Part 2 ball float valve in 1/2 inch high pressure specification. Used in cold water storage tanks, cisterns and ballcock assemblies. A straightforward swap-out when the valve body wears or fails.
The ball float valve 1/2″ Part 2 is the valve body section used in standard ballcock assemblies fitted to cold water storage tanks and WC cisterns. When a float valve starts to weep, fail to shut off properly, or simply wears out after years of service, it is usually the Part 2 body that needs replacing rather than the entire assembly. This makes it a practical, cost-effective repair rather than a full strip-out job.
Designed to high pressure specification, this valve is suited to mains-fed or gravity-fed systems where water pressure is sufficient to demand a more capable seat and seal arrangement. Low pressure valves are a common cause of frustration when fitted in the wrong application, so getting the pressure rating right from the start saves a return visit.
Where the 1/2″ Ball Float Valve Part 2 Gets Used
The 1/2 inch connection size is the most widely used in domestic plumbing. You will find it in loft tanks, WC cisterns, header tanks and similar stored water applications throughout residential and light commercial buildings. Part 2 refers specifically to the valve body component within the Portsmouth or Croydon-type float valve system, which has been a staple of UK plumbing for decades. The two-part design exists so that worn internals can be replaced without disturbing the backnut or the pipework connection, keeping the job clean and fast.
Plumbers, maintenance engineers and heating engineers all keep a stock of these to hand. A float valve failure is never convenient, and having the right part on the van means the job is done in a single visit. At this price point, carrying a couple as van stock makes straightforward financial sense.
High Pressure vs Low Pressure
High pressure float valves are designed to handle mains pressure or boosted systems. The internal orifice is smaller than a low pressure equivalent, which allows the valve to close cleanly against higher incoming pressure. Fitting a low pressure valve on a high pressure supply will result in a valve that never fully closes, causing the overflow to run continuously. Worth double-checking before fitting, particularly on older properties where tank configurations are not always what they appear to be.
This is a standard, reliable component that does exactly what it is supposed to do. No frills, nothing complicated. Just a solid Part 2 ball float valve in the size and pressure rating that most UK plumbing jobs call for.
Pro Tip: Before fitting, always check whether your system is genuinely high pressure by running a pressure test or confirming the supply source, because a high pressure valve fitted on a low pressure gravity feed will barely trickle and you will spend half an hour wondering why the tank is not filling.
This valve is used wherever a float valve assembly controls the water level in a tank or cistern. Cold water storage tanks in loft spaces, WC cisterns, header tanks for central heating systems and agricultural or light commercial water storage units all use this type of fitting. Maintenance plumbers and heating engineers reach for Part 2 replacements regularly, as the valve body is the component most likely to wear or fail over time in a working system.
Best For
Cold water storage tanks
WC cisterns
Header tanks
Ballcock assembly repairs
Mains pressure systems
Compatible With
Standard Portsmouth-type float valve assemblies
1/2 inch BSP pipework connections
High pressure mains-fed supplies
Boosted cold water systems
Key Specifications
Connection size: 1/2 inch
Pressure rating: High pressure
Component: Part 2 valve body
Application: Cold water storage
Not suitable for: Not suitable for low pressure gravity-fed systems where a low pressure rated valve is required. Not intended for use with hot water supplies or in systems exceeding the rated pressure of the valve.
Turn off the water supply to the tank before starting. Drain down the tank sufficiently to expose the valve assembly and give yourself a dry working area. The Part 2 body unscrews or unclips from the Part 1 base fitting depending on the assembly type, so no need to disturb the backnut or the pipework connection itself.
Fit the new Part 2 body, check the washer and seat are correctly seated, then reinstate the float arm and ball. Restore the water supply slowly and observe the valve closing action as the water level rises. Adjust the float arm position if the shut-off level needs setting higher or lower to suit the tank.
Isolate the water supply feeding the tank or cistern
Drain the tank to below the level of the float valve
Remove the float arm and ball float from the existing assembly
Unscrew or release the Part 2 valve body from the Part 1 base fitting
Fit the replacement Part 2 body, ensuring the washer and seat are correctly positioned
Reattach the float arm and ball float
Slowly restore the water supply and observe the valve closing as the water level rises
Adjust the float arm angle to set the correct shut-off water level
What is the difference between a Part 1 and Part 2 ball float valve?
Part 1 is the base body that connects to the pipework and is secured with a backnut through the tank wall. Part 2 is the valve body that screws into or clips onto the Part 1, containing the seat, washer and operating mechanism. Replacing just the Part 2 means you do not need to disturb the pipework connection, which keeps the job significantly simpler.
How do I know if I need a high pressure or low pressure valve?
If the tank is fed directly from the mains or a boosted supply, you need a high pressure valve. If it is fed by gravity from another storage tank positioned above it, you likely need a low pressure valve. A high pressure valve fitted on a low pressure supply will fill very slowly or barely at all, while a low pressure valve on mains pressure will fail to shut off and the overflow will run continuously.
Manufactured to suit standard UK Portsmouth-type float valve assemblies with a 1/2 inch BSP connection. The high pressure rating indicates the valve is designed to seat and close reliably against mains or boosted water pressure, with an appropriately sized internal orifice to match. The Part 2 designation refers specifically to the replaceable valve body component, compatible with existing Part 1 base fittings already installed in the tank or cistern wall.
Connection Size
1/2 inch BSP
Pressure Rating
High Pressure
Component Type
Part 2 Valve Body
Application
Cold Water Storage Tanks and Cisterns
SKU
10011331
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