Boiler bangs after treatments added

[jonhealy]

Hi All

My gas back boiler, a Glow Worm BBU 50, was making a little noise recently and reading around suggested it might be kettling. I drained a little water from a rad (which was clear, not black or rusty) and left a nail in it for a couple of days, which rusted. I hence concluded that they're wasn't enough anti-rust treament in the system.
I therefore decided to add a boiler noise reducer/descaler and an anti-rust treatement, randomly choosing Sentinel X200 and X100, respectively, both as concentrates injected through a rad bleed screw as per the instructions.
Since then (about two weeks ago), my back boiler clanks and bangs when running, which it never did before, though rads and water are both heating fine. The banging calms down a little as the system gets hot. I've bled all the radiators, all of which were fine. Being a back boiler, I've no idea how I might bleed the boiler itself? Is there anything else I might do. As the boiler is due a service anyway, I've got someone coming round in a week or so. Even so, I'd like to sort it beforehand if possible.
System is vented rather than sealed, pump appears to be running.
Have I dislodged some limescale and partially blocked a pipe somewhere?
Any other ideas?
Cheers, Jon.

 

[Agile]

Do you know for sure that the feed from the F&E tank is not blocked?

At the risk of making it worse, tie up the ball valve and then take about five litres out of the drain cock ( or a rad bleed screw ) and see if the level in the feed tank falls!

If it does then you may have air in the system. Look for air bleed points on your system.

Tony

 

[JohnD]

btw if you have a vented system (with an F&E in the loft) you can add your chemicals there, which can be easier and cheaper than injecting them

an old system is likely to have a lot of sediment in it, so you could have benefitted by using a desudger like X400 before using your X100 and X200.

 

[jonhealy]

Thanks for the help. I'll check the F&E tank over the weekend and try draining it as suggested. I used the injected concentrates as I didn't have a hose handy and can't fit a bucket under the drain cocks (they're sensibly quite low). I can't find any non-rad bleed points and I'd have to remove my gas fire to get at the bolier to check there. Guess it's probably not too much hassle...
If I go the X400 route, should I completely drain and refill the the system before adding it, perhaps flushing out any existing debris before starting, or should I just stick it in there? Is it worth leaving the X200 a little longer - it suggests a month of normal usage is required?

Cheers, Jon.

 

[JohnD]

First of all go and have a look in your F&E. see if it is full, the ball-valve is working, and the water level rises a little as the system goes from cold to hot. See if it has a lot of mud at the bottom, and bale it out (you don't want it to flow down and add to your sediment problems). Fit a lid if it doesn't already have one.

You can add X400 to the system without draining it. You will know it is starting to work when the radiator water goes jet black (this is with sediment it's loosened. An old system usually has a lot. If you hadn't just put £30 of chemicals in it, a plain-water drain and rinse would have been better as it will get out some loose stuff. Leave X400 circulating for a month as it is mild and quite slow.

If you add chemicals through the F&E, you have to drain out a bucket or two from a drain-cock so that the F&E replenishes it. this draws the chemical down into the pipes (also any mud you have not removed)

If you are fond of DIY plumbing, there are a couple of other things you can do, including fitting a Magnaclean which will trap the circulating black sediment once it has been loosened.

Sometimes old drain-off cocks need new washers, so buy a few before you start draining.

If you ask your boiler engineer, he will quite likely suggest powerflushing at a cost of some hundreds of pounds, which is great, but a chemical clean only costs you £15 and some of your time, so is always worth doing first and will do a lot of good. If it solves your problem you have saved hundreds of pounds.

 

[jonhealy]

I did check the F&E tank had water in it and that the ball valve worked. Tank was a little rusty brown round the sides and bottom but no real collection of sediment. What I didn't check was that the water went anywhere when the system is drained or if the level changed slightly when the bolier is cycled. I check over the weekend.

Once again, thanks for the help.
Cheers, Jon.

 

[Agile]

I used the injected concentrates as I didn't have a hose handy and can't fit a bucket under the drain cocks (they're sensibly quite low).

Cheers, Jon.

You are not expected to put a bucket under the drain cocks! They are intended for a hose which is why they have annular ridges.

You can usually get a plastic food tray under them to take a small amount of water out.

Tony

 

[jonhealy]

Yeah, I realised this but as I mentioned in my email, I had no hose available.

Thanks, Jon.