Need to drain and flush underfloor heating help

Bungusbeefcake

Hi all, I've had to replace all the upstairs radiators due to each one of them, in turn, corroding away and bursting. As such, I've just finished changing the last one. I've had rooms with the ufh stay freezing with no heat felt in the pipes coming from their manifold, so I'm going to do a rinse with Fernox F3 cleaner, then drain the system after a few days, then refill it and put in some Fernox f1 corrosion inhibitor.

I've a fair idea about most of how the system currently works but would like some help identifying components, if anyone can help.

Background, originally when we bought the place the boiler was shot and after replacing the boiler we found that there was a leak in the system, potentially in the underfloor part. The plumber eventually put in some radiator fix stuff which seemed to stop the leak, but the rads continued to corrode.

So what I'm thinking of doing is, I have a mains fill tube which I can turn on and off and I think I have a drain tube at the bottom which I stuck a hose pipe quick connector to. So I'll open that and rinse reach zone individually. Then, I believe, when I'm filling it up I need to open bleed valves on each zone....I've no idea where these are.

I would really appreciate all the advice you could give me.

Thanks

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