Boiler Leak Fixed Itself? Boiler Kettling X800?

[arh]

Hi

I have a Vaillant Ecotec Plus 637 system boiler.
I was getting some kettling so I decided to drain the boiler and refill to see if this would help by removing some dirt out of the system. I did the drain but when I tried to fill the system up I noticed that water was running down the black rubber pipe on the left side of the boiler. As this time the heating drain was open.

I called out a plumber that could not find any leak - he filled the system and it appears to be working well. There does not appear to be any kettling yet.
I do not understand why it was leaking and why it has suddenly stopped. Could having the drain open cause the issue?

I am looking at adding Sentinel X800 to give the system and boiler a clean and will leave this in for 24 hours. Is it worth doing this or could it cause more issues? Is this product safe to use?

I have 2 radiators that are not getting that hot so I was thinking to removing them and giving them a wash with a hose.

I will then fill and drain twice then finally add some X100 inhibitor. Is it also worth adding the X200 to help with the boiler kettling?

Thanks in advance.

 

[thereisawizza]

Are you on about the black rubber hose inside the boiler?

 

[arh]

That's right - the black hose - but no leak now.

 

[ianmcd]

If you are not familiar with using X800 I would use something milder the X800 can be very aggressive if not properly flushed out before adding inhibitor, the X800 is more suted for use with a powerflush machine