How to drain down a central heating system | chemical flush | add inhibitor

In this video we are draining down a sealed central heating system, which is often found with combination boilers. The water in this system is filthy and needed replacing as soon as possible. It’s critical that the water in the central heating system is kept clean and free from iron oxide/rust/corrosion or limescale, as these things can cause severe damage to the system and the boiler. To do a job like this, it is going to take several hours, so it’s best to have everything ready in advance and be prepared to spend the whole day doing this job.
Sentinel X 800 was used as a chemical flush for the system, because the original water was completely black (it looked like used engine oil). This was left in the system for 1 hour, with the central heating switched on. This was then drained out, and the system was re-filled again, this time a central heating inhibitor, sentinel X100 was added to the system.

[@GilesFleming-iy1sq]

Thank you for this video - when I drilled through a central heating pipe, it helped me through the process of draining the system, & saved me from a very expensive mess...

[@DjGiluk]

Excellent video, thanks mate 👍🏻👍🏻

[@ultimatehandyman]

You are welcome
Thanks for the comment 👍

[@michaelplays2449]

Great video, very enjoyable !!! thank you !!!!

[@ultimatehandyman]

I’m glad you found the video useful
Thanks for the comment 👍

[@Lc-is8vn]

Excellent as always 👍

[@ultimatehandyman]

Thanks for the comment 👍

[@daves4026]

Great video. I would also suggest you look at stopcore which I use now as they prevent the galvanic reaction, which the magnatec simply collects

[@ultimatehandyman]

Thanks, that looks interesting 👍
Do you have a Stopcor fitted?

[@sabakelelah]

Thanks useful

[@ultimatehandyman]

Welcome 😊

[@Petertronic]

Did the system have inhibitor in it already? Does it stop working after a while? Great video full of good tips, as ever.

[@ultimatehandyman]

Yes, as far as I am aware. The whole system was power flushed and the magnetic filter was installed when the boiler was replaced.
I think the black coloured water was caused by oxygen getting into the system from three leaking gate valves.
Hopefully it will be ok for the next few years. I think inhibitor can dilute over time, as you can purchase a test kit to ensure the inhibitor is still working.
Thanks for the comment 👍

[@Pete.Ty1]

👍👍👍Thank you

[@ultimatehandyman]

Welcome 👍

[@stiiffyrabbit]

i subscribed!
My boiler has a radiator warning light - it won't fire the rads up - a DHW thermistor error, so i'm told.
i have the inhibitor but, the problem of sludge/sediment remains, at least, something is blocking something!
before i buy cleanser, do i need sludge removal too? is there a procedure for it?
thanks, in advance.

[@npatrcevic]

Have you ever had bad experiences using the system cleaners? I heard stories of boilers and radiators being eaten up by the acid and starting to leak.
I'm going to expand my own system this spring/summer so sharing any bad experiences would be welcome.
Great video, as always, thank you!

[@ultimatehandyman]

This is the first time I have used them, and I only did that because I saw the colour of the water when I fixed a leak on a upstairs radiator. In your case, if you are worried about the chemicals causing damage, you could always do a power flush. I’m sure you can hire the equipment, if you want to do it yourself.
Thanks for the comment 👍

[@npatrcevic]

@@ultimatehandyman Thanks for the reply and the suggestion. The modern gas boilers have thin walled heat exchangers and are not as over engineered as are the older types. Plus, my neighbor had a bad experience with regular cleaning. Once in 10+ years shouldn't hurt. Wait and see :)

[@MrGh421]

​@@npatrcevic use a cleaner that's safe for aluminium heat exchangers

[@iansharp0306]

Hi, does your procedure remove all the cleaner from the system? I was going to do exactly the same as you, but have been advised that some cleaner would still be in the system and can cause problems/damage to system. Would it be ok to add cleaner, run for a few days, drain down, refill and drain again, then fill and add inhibitor?
Thanks for your videos, they have helped me loads

[@ultimatehandyman]

Yes, the more times you flush the system after the chemical flush- the better!
Thanks for the comment 👍

[@iansharp0306]

@@ultimatehandyman 👍

[@garvielloken3929]

NOOICE!

[@ultimatehandyman]

👍

[@johnfithian-franks8276]

Hi, my system is a direct boiler system without a header tank their has be a slow leak that I have now sorted but I notice the flexible pipe had a small hole so I am unable le to refill until I replace the hose. Is it save to remove the hose and what size are the two nuts on the pipe.

[@ultimatehandyman]

Hi John, yes you can remove the hose, just make certain that both valves are isolated.
They are normally 1/2BSP, but they can normally be screwed on by hand (not sure what that type of flexi is called)- www.plumbingsuperstore.co.uk/product/part-l-combi-filling-loops-15mm-straight.html?msclkid=909714057365170f19d377f74940a47d

[@johnfithian-franks8276]

@@ultimatehandyman thankyou very much

[@MrLear1976]

Quick question. My central heating is on a new build. All 4 downstairs ones are fed from pipes down from the ceiling. Does this mean after draining all of the upstairs from a downstairs I’ll need to drain the other 3 as they’ll still hold water due to the up pipes from each one?

[@mr.critic]

👍👍👍👍

[@ultimatehandyman]

👍

[@wontfindme1289]

A job for the pros or an expensive mistake for that miserable know all. 😂

[@ultimatehandyman]

😂😂😂😂😂

[@Mike_5]

Combi boilers are very nasty to the flow and return water in their system

[@ultimatehandyman]

👍

[@nickayivor8432]

👍
My Mentor Ultimate Handyman
INTELLECTUAL Ultimate Handyman
From Nick Ayivor from London England UK 🇬🇧 ⏰️ 07:37am Good Morning 🙏 🌄

[@ultimatehandyman]

Thanks Nick 👍