Guidelines and Installation

When installing Stuart Valves, if several points are carefully watched, complete satisfaction will result.

It is important that the valve supply tank must be of adequate size. Plumbing Regulations set down 90 litres for the first flush valve and 45 litres for each successive valve. We advise a little extra on this and strongly suggest all tanks should be provided with covers to keep out foreign matter. A gate valve shall be provided in an accessible position for each flush valve not fitted with an approved isolator. Provided that there are more than 3 flush valves in a range, additional gate valves shall be provided, so that not more than 3 flush valves are served by each gate valve.

Where there are two or more ranges of flush valves there shall be a gate valve provided close to the storage tank. If flush valves are provided with isolator valves these gate valves would not be required.

The following table is soley a guide to the number of valves which can be operated by a given size of supply pipe.


Valve performance can be affected by the length of horizontal supply lines and the number of bends, allowance for this must be made.

A minimum head of 2.5 metres is recommended for the water supply above each valve, measured from the bottom of the tank, with this low head, tank must be directly above valve and no more than two bends used. Do not use elbows. In the case of multiple heads a Stuart Isolation valve should be used to regulate the flow and facilitate servicing. Water hammer will not occur with the Stuart Flush Valve.

In the use of low heads of water, care should be taken to keep horizontal runs and sharp bends to an absolute minimum and care should be taken that bends, elbows, gate valves and horizontal lengths of pipe do not absorb all the head of water available.


On all multi-storey installations, the tank recovery must be adequate. When it is realised that each valve passes 90 litres of water in one minute, it will be seen that the tank feed must be large. We suggest that either one 40mm full-flow ball-cock or two or more 19mm ball-cocks (installed in parallel) be provided for. The main pipe feeding the tank should be no less than 25mm in diameter and should be 40mm or larger when forty or more valves draw from the same tank.

When installing the valves, be careful not to allow trimmings, from pipe or tank or any other foreign matter to enter the pipe-lines, as this will cause the valves to cease functioning.

As all flush valves are hydraulic, they require water to operate them. It is therefore MOST IMPORTANT that enough pressure remain at the valve, i.e. 14 Kpa minimum WHEN THE VALVE IS OPERATING as this will force the water through the by-pass hole to close the valve off. NOTE: The valve will not close off with no water or even with a trickle.

On the concealed model Stuart Valve, the pushbutton installation is simple. Merely drill a 22mm hole through the wall in a vertical centre line with the flush pipe, 57mm below the top of the valve cap.

It is important to make sure the pushbutton housing is locked onto the wall surface by tightening the back nut and that the adjusting tailpiece of the button is locked to the plunger by the hexagonal nut provided. If this is done, there will be no problem attached to these push button extensions.

There is an adjustment provided on Stuart Valves to vary the length of flush and thus the amount of water discharged at each operation.

Remove the button and retaining nut on the valve when a loose plunger assembly will be exposed. The head of this assembly is hexagonal and there are slots suitably arranged in the housing. It will be noted that the end of this plunger is machined eccentric and, depending where this is set, so the length of flush can be varied. The maximum flush occurs when the eccentric is at the top of its movement and the minimum when it is at the bottom.

When re-installing the plunger, it is important to engage the hexagon on the pusher with the slots in the housing, otherwise, the control will jam. When leaving the factory, the setting is for 11½ litres to be discharged in one cycle and in nearly every case, this does not require altering. However, where water supply is a problem, it has been found advantageous to reduce the quantity of water passed at each flush to 9 litres, i.e. eccentric on bottom position.

The Stuart Valve should function perfectly for an indefinite period. The only circumstances likely to cause mal-function could be dirty water depositing sediment or a slime deposit on the internal working parts.

Should this occur it may be neccessary to remove the top cap, take out the plastic piston and clean the surfaces inside the cap also on the pilot valve and plastic piston. It will then be noticed that UNDER THE FLANGE OF THE CAP IS a very small by-pass hole. IT IS VITAL TO MAKE SURE THIS HOLE IS CLEAR as this is the only access for water travelling to the top of the piston and closing off the valve.

Should hammer develop at ay time, it is only caused by a loose plastic piston. The remedy is to replace with a tighter piston.

It is most important when the Stuart Valve is re-assembled to use the special gaskets provided. On no account should hemp or sealing compound be used on this joint.

Every “Stuart” Valve is guaranteed for 12 months from date of installation against faulty materials and workmanship. This guarantee is made providing the valve is correctly installed and operated on adequate supplies of clean water. The manufacturers cannot be held responsible for any expense incurred in removing or replacing valves.