Bristan [E3] fault codewhat it means and how to fix it

E3 is the most owner-friendly of Bristan’s error codes and it is worth knowing that before booking anybody, because two of the four causes they publish are free to rule out. The code is about the shower not seeing the water it expects. Bristan list a solenoid valve stuck open or closed first, with a check that its blue and brown cables are fully connected to the power supply board before the valve itself is suspected; a possible blockage second, remedied by removing the filter and showerhead and cleaning them; a water isolating valve closed third, remedied by opening it fully; and a faulty flow sensor fourth, with a connector check before replacement.

The flow sensor is the component that makes the whole appliance work safely. An electric shower must never energise its elements unless water is genuinely moving through it, so the sensor reporting flow is what gives permission for everything else. When it reports nothing — because there really is nothing, or because it cannot see what is there — the shower declines to heat. That is why a stuck valve, a blockage and a failed sensor produce the same code: from the appliance’s point of view they are the same observation, no water where water was asked for.

Of Bristan’s four causes the two an owner can reach are the middle pair, so the practical order is the head and the filter, then the isolating valve, and only then the two behind the cover. Their check for the sensor itself is the same pattern as their other codes: before assuming the part has failed, confirm the cables connecting the flow sensor to the power supply board are fully connected at each end — red, blue and yellow. That is behind the cover and not an owner job, but knowing it exists is useful when the engineer arrives.

1. 1

   Check the water isolating valve on the pipe feeding the shower is fully open. Bristan list this as its own cause and it is the fastest thing to rule out.

2. 2

   Remove the showerhead and clean the spray plate, which is the first half of Bristan’s blockage remedy.

3. 3

   Isolate the shower at the pull cord, close the servicing valve and clean the inlet filter — the other half of the same remedy. On a Bristan the filter unscrews from outside the unit with a large flat-blade screwdriver.

   Pull the cord before touching the plumbing. Bristan’s own instruction for the filter is to isolate the electrical and water supply to the unit first, and a little water runs out when it comes away.
4. 4

   Restore the water, run the shower and see whether E3 clears. If it does, the restriction was the cause and there is nothing further to do.

5. 5

   If it persists with a clear filter, a clean head and the valve fully open, the two remaining causes are the solenoid valve and the flow sensor, and both are behind the cover.