Keep power shower (off) with unvented cylinder

[Akustik]

I'm about to start the process of replacing my vented hot water tank with an unvented cylinder.

Currently, I have a power shower installed (Aqualisa Aquastream). I've been told that I can't use that with an unvented cylinder.

Would I be able to keep using it for a while if I simply unplug the pump element from the power socket and use it as a normal thermostatic mixer?
Would it be a problem if I try and use it with the pump for a minute or two? I might try to sell it second hand before replacing and want to demo it.

Do they make thermostatic mixer showers that would fit pipe layout that's the same as one for a power shower (pipes being closer together)?

Is there a way for the pressure relief pipe to not go outside?

 

[muggles]

The main issue will be whether the internal fittings are able to cope with the increased inlet pressure, which will be three times their design maximum. I suspect that, pump or no pump, you'll kill it fairly quickly and it'll leak.

I don't know of any direct replacements. Do the pipes in the wall drop down from above, or come up from below?

An unvented cylinder's pressure relief pipework almost always has to go outside. It can also be run to a soil stack provided the correct materials are used.

 

[Akustik]

@muggles Thanks for your answer.

I don't know if the pipes come from above or below - the power shower was already installed when I moved in.
That's a shame, I was hoping I could keep using it until I did a bathroom remodel.