Keraflo Aylesbury ‘KB’ Type Float Valve (Delayed Action) WRAS Approved Valves

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Keraflo Aylesbury 'KB' Type Float Valve

Keraflo Delayed Action Float Valves For Cold Water Storage Tanks – WRAS Approved Valves

Keraflo Aylesbury ‘KB’ Type float valves are fully variable delayed action type valves, WRAS approved, suitable for use in cold water tanks with or without raised valve chambers.

The Keraflo ‘KB’ type valve does not immediately open when water is taken from the tank and the water level falls. Instead, there is a delay and the valve does not open until the water level has fallen by a user selected level.

When this occurs, the Keraflo ‘KB’ type float valve moves from a fully ‘closed’ position to a fully ‘open’ position allowing the water to flow in a return to the tank to its original fill level.

Keraflo Aylesbury ‘KB’ Type Float Valve – Product Benefits

Keraflo Aylesbury KB valve’s weighted float can be adjusted to a virtually unlimited range of opening and closing positions, allowing the tank’s stored water level to be easily modified.

Keraflo Aylesbury KB valve is suitable for installation directly into a tank or raised valve chamber and is lightweight, reducing tank wall stress and avoiding the need for a supporting structure.

The positive action and full bore flow delivered by the ‘KB’ type float valve provides further benefits such as good water turnover fast refill, the eradication of water hammer and reduced noise.

Keraflo Aylesbury ‘KB’ Type Float Valve – Product Sizes

 Float Valve Size & Type3 ⁄4” (20mm)1” (25mm)1 1 ⁄4” (32mm)1 1 ⁄2” (40mm)2” (50mm)
Standard Flow (SF) ✓
High Flow (HF)


 Cold Water Flow2 1 ⁄2” (65mm)3” (80mm)
Standard Flow (SF)
High Flow (HF)
Reduced Bore (RB)

Keraflo –  How the Aylesbury KB type FLOAT valve works

Keraflo ‘KB’ Type Float Valve Open & Closed Position

Keraflo Aylesbury 'KB' Type Float Valve (Delayed Action) WRAS Approved Valves

Keraflo KB Type float valves provide improved water turnover, reduced risk of legionella and energy savings due to positive pump control.

Keraflo ‘KB Type’ Float Valve – Pre-Installation Checks

When installing the Keraflo Aylesbury ‘KB’ Type Float Valves, there are a number of pre-installation checks and instructions that must be carried out and followed in order for the valve to operate effectively.

The range of pre-installation checks that should always be carried out are:

Minimum Tank Depth – Keraflo KB Type valves can be used in a tank which is at least 1.3m deep for KB40HF, KB50SF, KB50HF, KB65SF & KB80RB and 1.0m for KB20, KB25, KB32, KB40SF.

Raised Valve Chambers – The Keraflo Aylesbury K type valve should not be used with raised valve chambers. Instead Keraflo KAX or KB float valve should be installed.

Operating Space – There should always be sufficient clearance in the area the valve is to be installed within and the working dimensions are shown on the drawings available in the installation instructions.

Overflow/Warning Pipes – The position of the overflow pipe should always be checked and within the product drawings this will be labelled as ‘R Max’. 

Turbulent Water – In applications with exceptionally turbulent waters such as cooling towers the float should not be placed directly above. Calming measures such as baffle plates or still ponds should be used in these applications.

Flanged Tanks – The design of the KB type float valve allows sufficient clearance between the float and most internal tank flanges and ribs. The valve backnuts can be adjusted to enable the valve to be fitted to tanks with large flanges if a 20mm gap exists between the float and tank wall throughout the arc of the float.

Round Tanks – The minimum diameters required for use of the valve in round tanks are:

Float Valve¾”1″1¼”1½”SF1½”HF2”SF2”HF2½”SF3”RB
Min Tank Diameter (M)0.5m0.5m0.6m0.6m0.8m0.8m1.8m1.8m1.8m


Sloping Tank Wall – The wall to which the KB type float valve is to be installed on must be vertical and if the wall is sloped then tapered washers must be used.

Pipework Support – The range of Keraflo float valves create virtually no tank wall stress. It is not necessary to to provide additional support to the pipework as long as the Code of Practice for the Support of Pipework in general is met.

Isolating Valve – An isolating valve must be fitted as near is reasonably practicable to the Keraflo KB float valve.


Contact T&D Technical Team with the following information to enable the correct specification of Keraflo float valves :

  • State the application (e.g break tank, gravity tank, rainwater tank, sprinkler tank etc)
  • What is the float valve flow rate required?
  • What is the line size (supply pipe bore)?
  • What is the water supply?
  • Depth of tank (from supply inlet to tank floor)?
  • Does the tank have a raised valve chamber?
  • Do you have a requirement for monitoring and control? (e,g level and temperature monitoring, alarms etc)?
Keraflo Float Valves

Keraflo Float Valves – Contact T&D for Aylesbury float valves manufactured by Keraflo


Keraflo’s 20 page UK Water Supply – A Guide to Regulations highlights the design implications of this legislation with regard to float valves. This highly informative A4 document explains air gap types, fluid categories of risk and explains in detail the system design implications of the most common air gap types.

A Guest Blog by Keraflo, manufacturers of Aylesbury delayed action float valves and digital tank management systems. The article stresses the importance of installing WRAS Approved valves ensuring the protection of public health by preventing contamination of public water supplies.

Float Valves

More than half of all cold water storage tanks sold in the UK are fitted with a raised float valve chambers read more…….

 ➡ Did you know? T&D supply VEGA Level Sensors for level, point level and pressure measurement.

Thorne & Derrick are suppliers of a complete range of float valves, water management and water metering products.