Fernox or not?

[Johnny B Good]

Some of you may remember my saga with the Honeywell V4073A1062 zone valve. Well, fear not, all I have to say about that is that I've successfully finshed said repair, and more economically than I was expecting considering that I had to use the upgrade kit *and* purchase a new control head.

This now brings me to the expense (or not) of flushing out and refilling the system with a suitable mix of corrosion inhibitor. If I choose to use Fernox MB1 as I've done on previous occasions, it's going to cost well more than the 45 quid I spent on parts (and that's excluding the flushing/ cleaning additive cost).

I figure my system must have a 50% larger capacity than the typical ballpark figure of 100 litres oft quoted for a 10 rad 3 bedroomed semi- detached property so will need to buy a couple of 4 litre packs of Fernox to properly dose the system with.

ISTR seeing 4 litre packs of MB1 at a reduced price circa 27 quid or so somewhere on the internet a day or two back. Looking at the Plumb Centre web site, I see it priced at a whopping £54.37!!! a far cry from the price of the products sold in Toolstation around the 7 or 8 quid mark for a 1 litre quantity required to dose the eponymous 100 litre 10 rad system (MB1 uses a 4% dilution hence their 4 litre pack size).

The 7 to 1 price differential does rather beg the question as to whether or not the quality of the Fernox products can be 7 times or more greater than that of "The Cheap Stuff"(tm). There surely can't be *that* much disparity between these products, can there?

Anyhow, as I'd previously mentioned. on the two recent occasions when I'd part drained the system down to deal with the 3 port valve, the water exited the ground floor drain port looking crystal clear (it might be a different story when it comes to a complete drain down involving buckets in the basement). Enquiring at the Plumb Centre counter suggests this is no bad thing.

I've not experienced any of the classic symptoms associated with a sludged up system (no cold spots in any of the rads, no kettling in our ancient Ideal Mexico Super 100 boiler) so I'm left wondering if the prior use of Fernox MB1 has been the reason for our thirty year old system still functioning so well despite the complete lack of any regular annual maintenance work in all of that time.

As far as I can recall, the last time I flushed the system out and re- dosed it with MB1 must be a good 10 years ago when I replaced the pump where I was forced to do a part drain down in order to replace the isolator valves which had started leaking at the spindle glands.

Unfortunately, the only definite clue I have is that I dosed the system back in 1998 or so according to the labels I tied to the pipework by the boiler and in the airing cupboard, I find it hard to believe that this

*was* actually the last time I treated the system (but it's a possibility).

Bearing all that in mind, does anyone have any sage advice to offer in regard of product recommendations?

[Capitol]

With a similar boiler I have never added inhibitor to the water. I have had one rad fail in ?40 yrs, which cost a lot less to replace than the Fernox! The fact that the system is drained down every few years for modifications may be helping. The system has been filled with softened water for the last 35 years.

[Johnny B Good]

====snip====

Thanks for the speedy response. In view of the fact that the plumbing is the usual inevitable mix of steel and copper, I'm not so sure that it's a good idea to forego any corrosion inhibitor, especially as the intervals between full drain downs/ refills tend to be of the order of a decade or so.

I do feel that the use of inhibitor is a necessary requirement to stave off corrosion problems (hopefully for several more decades yet). Whilst the replacement cost for a single radiator pales compared to the cost of just a single 4 litre pack of MB1, one might well wonder how much longer the remaining rads might survive when that single rad failure may just have been the harbinger of doom for the rest of your 'fleet'.

I'm going to dose the system with some form of inhibitor, the only question is which brand? From your experience with a similar setup, I'm feeling even more inclined to use the cheap stuff. The pricing model for Fernox product smacks just too much of the one used by the infamous Russ Andrews of hyperpriced audio products fame for my liking.

[harry]

New radiators are much thinner than in days of yore so pinholes appear soon er. So if you have new rads then you need to go for it. If you have an aluminium boiler you need it. The stuff is not all the same, the stuff for systems with exotic metals (eg aluminium boilers) costs more. If there's no exotic metals, I would go for the cheap stuff.

[DerbyBorn]

Just remembered - I put some cleaner in a few months ago. I had better do a flush and put in some inhibitor.

[David]

Combi boiler warning - the manual for our Worcester Bosch very clearly states that softened water must not be used to fill the central heating side.

I assume this is to do with the sodium ions and the aluminium.

Cheers

Dave R

[Fredxxx]

And presumably an aluminium heat exchanger.

[Dave Plowman (News)]

My system was basically installed in the '70s. But has had a boiler change, and at the same time changed from open to sealed.

I have always used Fernox. All the rads are original. I've several friends living locally who've had to change rads which have rusted through.

When I changed the boiler, the instructions went on about a 'proper' clean and flush. But at drain down time with the old, the water came out pretty clear - not the black stuff you so often see. So I just flushed it with clean water.

The new boiler was fitted about 8 years ago. No problems with sludge or whatever.

So I personally consider Fernox worth the cost. No idea if there is a cheaper as good alternative.

[Fredxxx]

I've often wonder what the active ingredient(s) are in these inhibitors! I'm sure the raw material would be cheaper on ebay!

I recall some instructions where you drew off some fluid every so often into a jam jar and placed some bare nails in the fluid and replaced the lid.

If after a few days there was rust you needed to top up the inhibitor, otherwise all was well.

[Johnny B Good]

Thanks, Phil.

Whilst the strength of the MB1 inhibitor is at an all time low, I'll run the system up to maximum demand and take a closer listen to the boiler for any signs of kettling.

I suspect the greater pressure in the boiler helps to suppress such symptoms. It's in the basement at the lowest point of a rather extensive plumbing circuit that reaches up to a second floor set of radiators. I reckon nearly twice the pressure of vented systems installed into a typical two floor semi.

The pump, located as it is in an upstairs airing cupboard, is probably seeing only half that pressure so is another candidate worth monitoring for cavitation noise. That's remained almost totally silent in operation ever since it was installed about a decade ago.

Obviously, I'll be doing further testing with unadulterated 'tap water' which will provide me with a benchmark by which to decide whether or not Fernox MB1's kettling noise reduction feature[1] is likely to be in any way useful.

[1] And, likewise for any competitor products I may choose.

[Johnny B Good]

Glad to be of service! :-)

[Johnny B Good]

I've only ever used Fernox myself which, going by own experience and postings I've seen in this news group about CH problems, suggests that it just *might* be an extremely effective product indeed!

Otoh, it may be no more effective than any of the cheaper brands for all I know, having as it were, no experience whatsoever of those cheaper brands, the very existence of which, all rather begs the question as to whether or not the expense of Fernox product really *is* justified.

Right now, I'm really non the wiser.

[Johnny B Good]

Yes, I saw that very same advice quite recently in this NG. However, all that can really reveal is how effectively the dissolved oxygen content has been removed from the water/inhibitor mix which may not necessarily be the only or major protection mechanism against corrosion in a mixed materials plumbing system (essentially steel and copper components with a bit of brass and cast iron thrown in for good measure).

Having said all that, this may still be a reasonable indication of overall strength of the whole cocktail of inhibitants used in the inhibitor's formulation. I suppose *some* indication is better than no indication at all.

Better still would be if the maker of the corrosion inhibitor is able to supply a cheap testing kit to verify the efficacy of the water/inhibitor mix. Do any of them provide such testing kits?

[Charles F]

Yes, but not cheap - see

Having said that, I've got a pot of test strips that are way out of date, but still appears to be working fine. My system fernox mix tests OK, and measuring a quite diluted mix does show that the concentration is low.

So although they are expensive you do have them for quite a while.

Charles F

[Johnny B Good]

Ouch! £37.31 for a tub of 50 test strips! At that price that aught to be a lifetime's supply for a young married (at age 18) couple planning on passing them onto to their grandchildren.

Still, I suppose you could delay their purchase for the decade it'll take to get over the shock of the initial purchase of a couple of 4 litre packs of MB1. After all, if Fernox is *so* much better than 'The Cheap Stuff' as implied by the price differential, it's going to take at least a decade before there's the slightest worry over the efficacy of the initial dosing. :-)

Thereafter, assuming the 10 year test shows little deterioration, you can shorten the interval to 5 years until it finally starts to show that it's time to take out another loan for a fresh pack or two of 'The Good Stuff' and start the cycle over again.

Assuming a conservative 20 year lifetime for the MB1, that tub of test strips should last, let's see now... 330 years! That seems a massive level of 'provisioning overkill' to me but I'm guessing Fernox's target customer in this case is your 'jobbing' CH engineer.

I suppose if you can't persuade your local friendly jobbing CH engineer to sell you a 'pack of ten' for a tenner, you could always try getting another four households to form a purchasing syndicate with you (10 strips each should be good for 70 years' worth of monitoring I reckon). Mind you, this only works out if the durability of the Fernox treatment can match its price promise.

The big question is:- Can it *really* be *that* good? If the answer to that question is "Yes!", any early drain downs due to unplanned repair works will see you collecting the effluent in 55 litre drums for recycling (two in the case of the oft quoted 100 litre 10 rad example system, or in my case, three!).

There's one big plus point in favour of using the cheaper stuff, even if it works out just as expensive in the longer run, you won't be worrying about where you're going to acquire a pair or three of 55 litre drums from. :-)

[PeterC]

I'm using CalChem and it seems to work

More details and other treatments at

[Johnny B Good]

CORRECTION!

The figure "55" which I used is a reference to the classic 55 GALLON drum size which, to my surprise isn't *just* an approximation to 250 litres, it *is* 250 litres (well, using the 1 gallon equals 4.5454545 litres conversion factor on my eight digit calculator actually gave the answer 249.99999)! Which correction requires the following to read thus:

[ARW]

4.545454... is exactly 50/11

[Vir Campestris]

Google think 4.54609. I thought it was 4.5359237, assuming a gallon is

10lbs...

Andy

[Charles Hope]

Google gives the same as my BBC Metric Pocket book - and a gallon of water does weigh 10lb