So, I'm just
wondering if there is any way I'd be able to make use of this without
breaking regs or compromising the safety of the HW cylinder?

To do so, I'd have to bring the existing tundish down from about 1m high
to 30 cm off the floor (is that in itself allowed?), and add a tee into
the 22mm copper below the tundish, connected to a short vertical run
into which the 0.5" plastic drain hose from the dehumidifier would be
tucked. Diagram below.


Do not move existing tun dish. Max 500mm from cylinder to tundish is a
reg.

Without checking I suspect there are a number of regs that would be
breached.

what about a condensate pump and share the existing tundish?


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html