Have just drained and removed a radiator (second in a month) to allow for skimming the wall. Also released pressure in the sealed system as there is a TRV and the day is cold and I had no decorator's cap....
Should I be adding inhibitor before I put the radiator back on to compensate for that lost when the radiator is drained?
Does it matter if I mix two different types? Does it matter if I add too much?
All advice welcome!
Ta
David
You can improvise a cap - remove the TRV head, insert 5p coin and replace cap. That will keep the valve button depressed regardless of what the TRV does.
One rads worth on its own would probably not warrant it. However if it has been a while since you added some then it won't hurt.
Not usually.
You would have to add *lots* for it to be too much.
You only need enough pressure to get water to the highest radiator. You dont need inhibitor, some ruin seals. Once it has heated fully the oxygen is cooked out.
Not sure I would agree with that in all cases. Some boilers will have an under pressure lockout that will prevent them firing with the primary pressure below a certain threshold. You also need to allow for the possibility a boiler is fitted above the rads (i.e. in a loft as is common these days).
There is a grain of truth in some of that, but as stated is rather too general for my liking.
A sealed system *should* be less vulnerable to corrosion since there ought not be a route for fresh oxygen to enter the system once the O2 dissolved in the water has all reacted with the metal components of your system. However this does mean that all the initial O2 will result in corrosion, as will any that is added later following radiator drain downs, or as a result of leaks being "topped up". So having a corrosion inhibitor in from the start should eliminate that initial corrosion and top up related corrosion. Obviously with vented systems there is open access to free O2 and the inhibitor becomes far more important.
There was some concern that high concentrations of inhibitor could affect some types of seals. However that is mostly a thing of the past since current products (and for that matter sealing materials) don't exhibit this problem. The main downside of over dosing is simply one of cost. Most inhibitor manufacturers also make test kits that allow you to test the concentration.
Finally corrosion inhibitors are not only O2 scavengers, but are also designed to have other beneficial effects. They may also include: a pH buffer to maintain the pH at roughly neutral levels. This can reduce the likelihood of pinhole leaks forming. They may offer anodic protection - in effect coating metal surfaces to prevent ion migration and hence eliminating or dramatically reducing galvanic corrosion and hydrogen evolution. Also properties to reduce the deposition of scale - hence reducing boiler kettling/noise.
Many thanks for this - especially the 5p tip - could've saved myself a lot of worry....
David
Neat! I'll remember that.
Not my experience. I have seen plenty of sludge build up in a sealed system without inhibitor.
Sludge would be from bad water. A leak that allows new water to be added constantly and a hard water.
Not in a sealed system.
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