Having refilled my CH system earlier today I didn't add any inhibitor..mainly because I didn't have any but also because I expect to have to drain it down fully or partly quite soon again . How long is it reasonable to run it without any in ? ...also how do you calculate the capacity of the system .Alpha CD 32, 5 rads and a mixture of 22mm and 10mm piping on one level.
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I haven't had any in my system for 29 years. Conventional vented S-plan, soft water area if it makes any difference. Only "wet" failure is the pump, (on the third).
My father ran his central heating system for 50 years with no inhibitor in it. He had the same gas boiler from about 1960 onwards (coal before that) and had no major faults. That gas boiler was not new - it came out of next door's skip. Mind you, there was no pump to fail; the system was gravity circulated, no electricy involved at all.
Similar to my last Boiler ..a Potterton floor mounted Kingfisher .Was there when I moved in and eventually dumped 25+ years later when I got the combi.All I did to it was replace the seals on the heat exchanger unit.
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So likely large diameter pipes and rads with large water jackets, so unlikely to get clogged. Also made out of thick material - iron barrel and cast iron. And of course if gravity circulation it can't pump over and oxygenate the water. The snag sort of comes in with pressed steel rads - I've seen a number which have rusted through and leak necessitating replacement. Not so if inhibitor is used from new.
I've had inhibitor from new for last 20 years. When I've drained a (steel) radiator there's been no black, just clear, faintly-coloured liquid. There's no smell when I bleed a rad and none have leaked. Definitely worth doing. I used Fernox. Only drawback was some precipitation in the header tank, so try to drain the inhibitor into the system leaving just plain water in the header. Unless you don't have a header of course.
OP's question was how long was it safe to leave without, if intending to use it. Answer from all responses, no urgency. Wait till you get the system finally sorted - one month, six months - but then I think do put it in.
Me too - having recently fitted a new boiler to a near 30 year old system which has had regular changes of Fernox since new. As you said, near enough clear. For what it costs I'd say it's a reasonable precaution.
Although Screwfix sell No Nonsense stuff at half the price of Sentinel..Anyone use it? For what it is the Sentinel stuff seems expensive .
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My father installed their central heating about 50 years ago. It's all copper pipework (mostly 1/2") and what were then the new thin steel radiators (i.e. what we routinely use nowadays, but before they thought of the extra fins).
For the first 40 years, it had an Ideal Standard gas boiler, and changed to a Potterton Suprima 10 years ago (with a replacement circuit board from Geoff a few months ago;-)
The only time it had inhibitor was for one year when the Potterton was fitted. The original 50 year old radiators are all perfect, and never had any problems. Some additional radiators fitted 40 years ago lasted 20 years before rusting through, and their replacements have lasted 10 years before rusting through.
So I think the survivability of the system (radiators in particular) is very heavily dependant on how old it is. The first modern radiators (50+ years ago) are very much thicker and heavier than todays ones, which unless you want to treat as consumables, you have to be much more careful with.
OK... When I was small, our system ran without additives, due to having a primatic cylinder (no header tank - chemicals could bleed back into DHW supply). That ran OK for over 2 decades on an old Potterton cast iron boiler with 1",3/4" and 1/2" plumbing to pressed steel rads - though the water was black at every draining and the pump used to get stuck if left idle too long over summer (HW heating was gravity pumped).
I'm running my current system on clear water due to repeated drain downs and refills to remove random rads. Last draindown the water was clear, after about 3 months of running.
I think the only fly in the ointment might be the boiler - modern boilers with fine tubed heat exchangers might be more sensitive to scaling and sludging - but I don't really know for sure. I expect it would be OK for a short time (weeks???)
I'm going to have to cheat a bit on my next install. As I'm building incrementally a heatbank system (over 300-350l volume including rads and pipes) I can't afford repeated flushings and adding inhibitor each time I add a radiator. So I'm going to fill with inhibitor, add rads using isolator valves to avoid massive draindowns. When everythings in and proven, I'll do a full draindown, chemical flush and refill then.
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Stuart B saying something like:
Months, a couple of years, even. If corrosion took place so rapidly that the arse was to fall out of your new radiators within a few days, we'd be in serious shit.
One other thing about corrosion inhibitors: I removed a rad wit water inside it. I made the mistake of letting it empty onto the garden. All the plants died.
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