Using Central heating WITHOUT fernox inhibitor

[Kevin Brady]

Couple of months back I had to drain the CH system to remove an existing radiator and cap off the flow & return, while extension works (new kitchen) are being carried out. When refilling the system, although I had a bottle of Fernox (about £15), I thought I wouldn't put it in for a couple of months, until I had refitted the radiator and added one in a new location, which would involve draining down alll over again, and wasting the inhibitor.

With the colder weather upon us, the central heating has been switched on again and it's going to be another month or two before the radiators in question are reconnected. How long is it acceptable to run the system without inhibitor in it. If necessary I could put it in this weekend, but if it's not reeally necessary for a couple of months then I'll wait.

Thanks

[sPoNiX]

My central heating system is over 30 years old and for the last 6 years (At least) has run without inhibitor. It's possible it's never had inhibitor in it.

As long as you put the Fernox in next spring I personally wouldn't worry.

sponix

[Christian McArdle]

It depends. Some people run without inhibitor, although can be a disaster if serious corrosion sets in. I'd probably not want to run several months without it, although I would be happy for a week if there was no chance of freezing. You could buy some "value" inhibitor in the meantime, particularly if a "couple of months" turns into "a few years" due to the chronic tuit shortage.

Toolstation will do you a dose of inhibitor for 3.35 inc VAT.

[Set Square]

AIUI, it depends on the composition of your tap water. You *may* get away without inhibitor, but it's always *safest* to use it.

To the OP: Is yours a vented system? If so, can't you save the water and put it back into the header tank so as not to lose the inhibitor? That's what I do.

[andy hall]

You can even if it's a sealed system.

For my secondary circuit that provides heating to my workshop, I decided to use an inhibitor containing an anti-freeze - Fernox Alphi-11. To achieve what I felt to be a good margin of minimum temperature, several containers were needed and it is fairly expensive. I therefore fitted two filling points. One is in the house and mains water can be used in the normal way. The other is in the workshop together with a drain point. The expansion vessel is also in the workshop. I can isolate the garage part of the circuit from the house with two valves.

I made up a filling gizmo consisting of a garden sprayer with several plumbing fittings attached to the wand to adapt it to fit the filling point. I can drain part or all of the system and collect the water. I can then pump it back in using the sprayer. There is enough oomph in these things than I can just about get 2 bar, so in effect I can repressurise using the old water.

Since the sprayer is about the same cost as a dose of regular Fernox, it may well be worth something like this during extended plumbing operations.

[Kevin Brady]

Thanks everyone for the advice - its a vented system, but I think a few quid on some value inhibitor will protect my conscience for the next few months.

Wishing you a good weekend.

[Jerry]

When I tried using Fernox I had nothing but trouble. The sealing washers on the radiator vent valve fittings all disintigrated over a period of time and started seeping. I drained the stuff out and re-filled the system with fresh water. My understanding is that a given volume of water carries only so much oxygen and once it has reacted with the inner surfaces of the heating system then no further corrosion can take place anyway.

Jerry

[andy hall]

That is true for a sealed system as long as there are no leaking joints which can achieve negative pressure relative to the atmosphere. This can happen if the system pressure is allowed to fall to much.

For open vented systems, if there is any amount of pump over or suck down, then oxygen will be rapidly introduced. Even of "perfect", the header tank is exposed to the air and air will dissolve. Given that there will be expansion and contraction, there will be introduction of oxygen.

There should be no reason for vent valves to fail. It would be worth fitting a different type.

Omitting a good quality inhibitor is inviting an expensive replacement of radiators later.

[Andrew Gabriel]

Actually, it's worse than this. Even when the water pressure is higher than atmospheric pressure, oxygen will still enter the system through a leak when the partial pressure of oxygen in the water is lower than than in air, and this will nearly always be the case as the oxygen in the system will be continuously removed by reaction with iron (rusting). A leak which is too small to leak enough water out to notice will leak air in much faster (even when water pressure is higher than air pressure). To an oxygen molecule just outside the leak, your heating system will look like it's nearly a vacuum, inviting it in. Even if you don't think you have any leaks, things like the stuffing boxes on valve shafts and O-Ring seals on moving actuator shafts aren't going to be completely gas-tight, even if they appear to be water-tight. The oxygen will even leak in through the walls of some plastic pipe and fittings.

You can get a rough idea of the corrosiveness of your water by draining off a small jar full from a bleeding nipple, and leaving a small iron nail in it, with the lid sealed closed. If the system has inhibitor in it which is not all used up, the nail will stay shiny. Otherwise it will rust on the surface, until it has used up all the oxygen in the water. (Don't use a large nail -- the jar might not hold enough oxygen to show rust, even it it's saturated.)

[Rick Hughes]

How long is it acceptable to run the system

I had always used Fernox .... when I had my new system commissioned, my CORGI man (been in business 30+ yrs) told me he NEVER adds inhibitor, it is not needed and just a marketing ploy.

Interesting view form a professional.

Rick

[mike ring]

I find Andrew's explanation above (on *my* reader) to be somewhat more convincing.

mike

[gastec]

INHIBITORS.....FERNOX....SENTINAL ETC

In general terms they hold good for around 15 years with 3 complet draindowns.....IT IS NOT GOOD TO ADD CHEMICALS TO YOUR SYSTEM unles there is a specific reson...If you add fernox incorrectly it wil solidify and block your cold feed...its will then eat away at your pip causing a water leak..seek advise from a qualified gasman....if yo really want to enhance the lifetime of an old system..POWER FLUSH I

-- gastec

[Rob Morley]

A professional who will benefit from all those systems that need repair or replacement because they didn't use inhibitor?

[daddyfreddy]

It's certainly interesting, no question about that.

Without it you end up with loads of crap in the system.

[andy hall]

These messages brought to you by the Association of Heating Replacers and Unnecessary Expensive Solutions for the Gullible.

[Andrew Gabriel]

Well, that voids the manufacturers' warantees on most new boilers. Does he offer his own warantee instead?

Not really.

[<me9]

I too was starting to think it was from someone indoctrinated by the Monarch's dog's tail.

[<me9]

It was suggested by mine that I didn't need it in a sealed system, but If I really wanted to to add it after 6 months use. I did so 12 years ago and so far have had no (major) problems.

I wonder how long fernox lasts? I top up the system manually, and probably add no more than 5L per year of water.

[Dave Plowman (News)]

Well, of course. It's not in his interest to have a system last a long time. Just beyond a reasonable time for a legal warranty.

[Dave Plowman (News)]

The reason is to prevent corrosion to the steel parts like the rads.

So a corrosion inhibitor causes corrosion? Think you might be able to sue if it did.

Oh dear. The likes of you?

Ah. Now the plug for a vastly overpriced service.

If you've used the correct inhibitor there won't be anything to 'power flush' out.