Hi,

I moved into a new house 5 months ago and the downstairs rads never get
hot, whilst the upstairs ones get warmish. It's an 'open' system that's
around 15 years old and I don't know if inhibitor was used correctly.
I decided to drain the system down and remove all the rads, flush them
out with a hose, replace them and add some sentinel x400. The upstairs
ones are definitely warmer and I'm happy with them, but the downstairs
ones are still stone cold, so I'm not sure where to go next?
There was some very black sediment in all the radiators, but this
mainly came out in suspension when flushing through, rather than really
thick sludge that I'd been expecting. I only refilled the system last
night so should I wait and see if the Sentinel does anything? The fact
that the downstairs rads are stone cold makes me think that this is a
long shot!
The pump has 3 settings and it's currently on the lowest- I was advised
not to turn this up but could that be the problem?

This is my first attempt at plumbing and I was prompted by the high
quotes and un-convincing advice given by the plumbers that I've had
round (no offence to all you decent proffesionals out there!)

thanks
Charlie