We had a Mira Flight shower tray that we had fitted to an en-suite bathroom and all was all ok for about 18 months. Then it started to overflow the shower tray while showering because the water was not draining away quick enough.
We regularly cleaned out the channel drain waste chamber body and the waste pipe with special triangular and cone shaped sponges on sticks to make sure we got into all the nooks and crannies that Mira had designed into the plastic extrusions of the drain assembly.
We also used a drain cleaning coil with a brush on the end to make sure the waste pipe was totally clear. The drain cleaning coil meant that we could get all the way into the main waste pipe line to make sure the entire route was clear of all blockages.
To prove that is was not a blockage in the waste pipe we tested a sink further up stream which was draining away with no problems.
When we took off the channel drain cover and took out the waste tube insert the water would drain away quickly. Putting the waste tube insert back in would slow the flow of the water right down so we could only draw one conclusion. That conclusion had to be that the channel drain waste tube insert had somehow expanded over time pressing against the channel drain chamber wall and was inhibiting the flow of water from the shower tray.
Unlikely as it may seem the solution was to cut away some of the length of the waste tube and also to drill some holes in it as well to facilitate the water draining away at a better rate. This seemed to make a lot of difference and the water now drains away with a much greater vigour.
A more drastic solution might be to ditch the waste tube insert all together but this seemed to be too severe a solution as Mira obviously included the waste tube for a reason which was probably to catch any detritus that may make it through the cover but in our case it was also stopping the water which kind of defeats the object!