Timing of Rada T503 push button controls

[Stevet]

I have several Rada T503 push button controlled showers ( stamped as MIRA). The timing of each valve varies between 7 & 77 seconds and seems to change depending on which shower the valve is fitted to. Does anyone know where we can get a manual/instructions for the 503 push buttons ? What is it that governs the time the shower runs for - is it the water pressure ? is it the spring ? - Adjusting the screw thread at the back seems to make little difference - obviously I can buy the spares from showerdoc but I need to know which part/parts to buy & can't find a local plumber who understands them. Thanks in anticipation.

[The Doc]

Hi

The 503’s are not adjustable the length of time they run fore is dependent on pressure (and a little bit age!) The higher the pressure the shorter the time.

[Stevet]

As our boiler is gravity fed, my T503's on low pressure should be running for a very long time - but as some of them were probably installed in the early-mid 90's and only give a few seconds I suppose they have just died of old age . There appears to be only one model of the T503 - is this right ? I don't see how these work - is it friction from the rubber seals ? - main thing being will they just need a service pack T503/750 ( 936.75) or a cartridge assembly 902.79 to restore them For future reference - presumably then the "flow restrictor" ( part 146.04) simply governs the amount of water going to the shower head ?

[The Doc]

Sorry for the delay in replying but we have had problems with our system.

I would tend to fit new cartridges as they are easier to fit and not that much more expensive.

[Marcelo]

Thanks for letting me know about the new cartridges and I need to check the prices and some best cartridges you have added...!!!

[The Doc]

It is the water pressure and the age, or maintenance or the lack of maintenance, that alters the timing.
The screw thread adjusts how far the piston is pushed in which has the effect of altering the timing.

The options are to fit a service pack or the cartridge.

http://www.showerdoc.com/shower-spares/ ... 503-902-79

http://www.showerdoc.com/shower-spares/ ... 750-936-75

In either case make sure that the seals are well greased with silicon grease before fitting.