Too Much Inhibitor?

Is it possible to add too much inhibitor to a system?

I've had cause to replace a number of radiators, split into two batches, over the last few months and I have another three to replace next week. After this occasion I don't anticipate any further work on the central heating for some time as almost everything will be new at that point.

On the last two occasions, I've only drained down part of the system on each occasion, turning off all the other radiator valves so they remain full of water. Each time I have added a full 1L bottle of Sentinel X100 to the system, though obviously a reasonable portion of the first bottle would have been drained away on the second occasion when I replaced 4 radiators, and a reasonable portion will be drained away again next week.

I'm wondering whether I ought to add another bottle next week or not. By my reckoning I probably have somewhere approaching 150L of water in the system so 1.5L is the correct dosing, but not knowing if anything was in the system before I started, and not really knowing how much of the 2L I've added, I'll have drained out again, I really haven't a clue what's in there!

Is it safest to add another litre to be sure there's plenty in there, or leave it as is and simply top up with water next time?

 

Why not buy some litmus paper and get it spot on?

https://www.homebrewcentre.co.uk/litmus-papers-acid-test-ph-1-11-book-of-20-strips

 

What would I be aiming for with a litmus test?

I assume I'd want it to be non-acidic but would I aim for neutral or alkaline?

What would I see if I my inhibitor was either over-dosed or under-dosed?

 

https://www.ebay.co.uk/itm/Combi-Bo...40f9abb0c7823507bd68|ampid:PL_CLK|clp:2334524

 

How many radiators on your whole central heating system? As a rule of thumb I always use a 1 litre bottle to do 8-10 rads.
But to answer the first part of your question to much wouldn’t harm your system.
Every bottle has a dosage recommendation on the label.

 

Between 6.5 and 8.5

https://www.vaillant.co.uk/download...ty/vaillant-water-quality-leaflet-1915494.pdf

 

I could be wrong but I doubt a litmus test would tell you all that much about inhibitor concentration. Inhibitor test kits aren't litmus tests; they measure the relative quantity of the active chemicals (molybdates) that makes up the inhibitor.

Regarding the OP, most inhibitors I've seen say you can't overdose.

 

As a rule of thumb I agree, but recently some manus have been saying you can, and the strong inhibitor, reacts to some components in diverter valves causing components to swell up, personaly my own system is well overdosed and never caused any problems