Mixing central heating inhibitor

Any problems in mixing different brands of central heating inhibitor?

I've got to replace three radiators and, unlike previous occasions when I've been able to save the water I've drained before putting it back into the header tank, this time I'm likely to lose quite a lot. The current brand is one that I don't recognise and so I'm going to have to use another to top up with: Triple X (94504) from Toolstation?

TIA

Reply to
F
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I've asked the same question here before and been advised that it's not a good idea, so have not mixed types myself.

Given that you have the luxury of actually knowing what's currently in there, I'd certainly be inclined to track that down the same brand again to top up; better than having to flush out the whole system and replacing it (though that being said, given that the system's in bits anyway, flushing out shouldn't be too much of a pain.

David

Reply to
Lobster

I don't think there's much difference between any of them. Usually a mild acid, such as boric, and a surfactant to aid dispersion. Even if they're not all the same, I can't see them being incompatible

Reply to
Stuart Noble

We've got concrete floors so all the rads are on pipes that drop down from the ceiling which means 9 drain points (or 9 radiators to turn off in turn and then reset) if I'm not going to be pushing an ever weakening mixture of water and inhibitor around...

Reply to
F

Anyone got any experience of this brand?

Are they all pretty much the same?

Reply to
F

They're all mildly acidic. AFAIK the rest is hype

Reply to
Stuart Noble

One main active ingredient is Molybdenum. It is its concentration what is tested to assess if the system is corrected inhibited (like the Sentinel x100 Quick Test). Optimum concentration is 330ppm of molybdate

Molybdenum is expensive and I've been told by a manufacturer that its concentration varies across inhibitors.

Reply to
asalcedo

Manufacturer's instructions usually recommend that you don't mix them. This may be taken as a ploy to ensure they sell more of their own brand, but I wouldn't mix inhibitors.

Some brands ( Sentinel, I think) contain sodium molybdate which works by putting a coating on the steel surfaces. Other brands contain nitrites. I've been told that mixing molybdates and nitrites will generate ammonia and attack brass components. You may get some idea fom the COSHH data sheets, but you don't know what's in it and shouldn't mix them. I think the molybdate is the quality/expensive stuff.

Come to think of it, I was involved with a commercial job where water treatment contractors were given records of the existing inhibitors and still put the wrong stuff in. Much system failure, embarrassment and air locking resulted, followed by much flushing and very little discussion of what they'd done.

Reply to
Onetap

You've probably all lost interest in this by now, or you've mixed the inhibitors anyway.

There's a brief description here;

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are 4 types of closed-circuit inhibitors listed (sulphite, silicate, nitrite, molybdate) up to page 5, after which it goes onto open circuit and steam boilers.

Of these 4, silicate is the only one I haven't come across, the other

3 I know to be in use in CH inhibitor solutions.

So no, you definitely shouldn't mix them unless you happen to know that the active ingredients are the same.

Reply to
Onetap

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