Hidden cistern - inside cavity wall or remove blockwork?

[untrepid]

Hi, I'm looking at getting a Roca hidden cistern, which is only 78mm thick. I'd like to bury this in the external wall of an ensuite, below a window opening, as per this video...

But a cavity wall doesn't really match what they show there - i.e. bolting it onto a wall around 100mm behind the tiling level. That's where the cavity starts, not finishes!

So where does this thing go in a cavity wall, as from the tolerances it wants to pretty much float somewhere between the cavity and the blockwork. (the panel cut out appears to want to be between 22 and 75 mm from the tiled surface - http://www.uk.roca.com/catalogue/pr...8cm-dual-flush-424-5363l-110ø-elbow-890080110

I'm guessing the best approach may be to cut out much of the blockwork, put some simple 4x2 structure in at cavity level and have the cistern bolt to that, leaving the back of it flush with the back of the blockwork line? Then just aquaboard over it all?

As much as I like the idea of wiggling the unit in through the window opening and dropping it down, I imagine that'd be a nightmare and a terrible idea...

 

[bernardgreen]

A cistern in the cavity of an external wall ?

Think winter, cold and lack if heat insulation between cold brick work and the cistern.

You could add a frost stat and immersion heater to the cistern to protect it during the winter months.

 

[untrepid]

A cistern in the cavity of an external wall ?

Think winter, cold and lack if heat insulation between cold brick work and the cistern.

You could add a frost stat and immersion heater to the cistern to protect it during the winter months.

Well if it's level with the blockwork then all the wall insulation can remain in place, so there's that...

 

[bernardgreen]

In that video and like almost all installations the cistern is hidden behind a dummy wall built a few inches away from the real wall.

 

[untrepid]

Yes, seems somewhat unrealistic