central heating cleaning

[JAMES2]

I'm about to replace a radiator with a new one and I guess need to flush the system afterwards with Sentinel 300 for new systems. My question is having read the instructions is that it says leave in for at least one hour preferably with a warm system - but can I leave it in for even longer say for a week before I drain down again and replace with inhibitor?

Many thanks in advance

 

[Bahco]

I left mine in for 3 weeks, couldn't see it doing any harm. I drained down and added inhibitor.
See what the pros think

 

[kevplumb]

leave it in wont hurt