On 2007-01-28 09:50:55 +0000, Siggy said:

An alternative that would be better than adding a cleaner and
circulating would be to rent a pressure flushing machine and use that
to power flush the system.

'Tis an idea. Hadn't thought of that. But I liked the fact that the
DS40 states it *would* return the rads and pipework to bare metal
condition. :-s

The concern is how much metal it will remove in the process. The
effectiveness also depends on how much crud there is because the
solution can only dissolve so much. Is it at a level where the
bottoms of the radiators feel cool in the centre?