Vaillant boiler - to treat or not?

[PeterC]

Just finishing off adding a rad. and other jobs on the CH system, then do a simple service on the boiler.

It's a Vaillant EcoMAX 824E, about 11 years old. The manual doesn't mention any sort of treatment to put in to the system and the installers said that it wasn't necessary, but there was a small amount of black stuff in the rads (I took them outside and shook the s**te out of them). The drined of water was clear and colourless.

Just wondering if there should be anything put in and, if so, what to use.

Also, I've had little luck in looking for a source of spares so don't want to go too far as there's a major gasket that almost certainly won't survive dismantling.

OK, 11 years of use is a goodly time, but it's off for 5 months a year and v. little use of DHW so not much used by normal standards.

Any info. gratefully received.

[A Plumber]

I always used an inhibiter in CHS in mine I used Fernox mb1 which is for cast iron heat exchangers. not sure whether he Vaillant is cast iron or copper, but get the proper inhibiter to put in. the system will run better, stops the boiler "kettleing" and longer for it, as you should not get the black sludge formimg.

[Dave Plowman (News)]

I first installed my system some 30 years ago and have always used inhibitor. Changing it every 5 years or so. Recently installed a new boiler - old one still worked but wanted a more efficient one. All rads original and have never given problems. Just about everyone I know has had one or more rads replaced due to them rusting through - often in much less time than this. Also, on the odd occasion I've removed one for decoration etc, they've not been full of black gunge so often reported here.

I'm not surprised makers and installers don't 'recommend' inhibitor. After all they want to sell you a new system as soon after the existing one as possible.

FWIW, all cars use some form of inhibitor in their cooling systems too. In the days when they didn't you'd get things like blocked rads...

[VAG_dude]

Sta "Thank you for your email regarding the Fernox F1 and MB-1.

MB-1 is a product we have produced since the 1960=92s and as such is widely recognised by many in the heating industry. Fernox F1 and MB-1 are essentially the same. The F1 is a concentrated form of the MB-1, thus less packaging and reduced shipment costs associated with a lower volume. Fernox F1 and MB-1 are essentially the same in terms of metal and scaling protection and life expectancy in use (i.e. 10 years).

We trust you will find this information of help and assistance."

Two Vaillant boilers in my family that I have done a little bit of work, one has Sentinel X100 and was powerflushed with X800 and the other has Fernox F-1 and was flushed with Fernox F-5.

[Dave Plowman (News)]

If you've always used a decent inhibitor it shouldn't need a flushing chemical as there should be nothing to flush. ;-)

[VAG_dude]

Yep, however in my case the systems had not been protected for a few years which is why they required flushing first before adding an inhibitor.

[PeterC]

Useful stuff, thanks.

Bit of a problem flushing: the 2 drainage points have washers with about 3

- 4mm holes - water does little more than dribble out. I don't know if I could remove the washers temporarily to get a decent flow.

The system's had 3 Bar air in it for 18 hours now (that was a bloody job!) and the gauge is still dead on the mark - looking good.

[PeterC]

Looking at Toolstation's site (need to go there tomorrow to take something back) and came across CalChem. I wondered if that'd be any good. The home site is

almost too good to be true.