Drain refill, drain refill, drain refill...

[mike42]

So after flushing the system (vented with FE tank) with x400 for the last few weeks, I've come to flush it out. I got the idea part way through to instead of fulling draining and refilling several times until the water runs clear, to keep the CH pump running (boiler off), whilst draining from a lower RAD whilst allowing fresh water to run into the FE tank (at a faster rate if needs be than what I'm draining). MY theory is that the pump will keep mixing the water around while the system slowly gets cleaner.

Its a big system with a lot of rads so I'm hoping this will speed up the process. Does it seem like a reasonable thing to do or is it daft?

 

[mike42]

Well a few hours later the water is almost running clear. On the plus side I don't have to go to all the RADs, open their vents, close them and finally bleed them. I'm hoping it also means I'll be cleaning out the water in horizantal pipes that are below the bleed off point. The minus point is I'm really not sure what I'm doing !!!

 

[Madrab]

Only thing I'll say is Mike is it may not allow all the areas of your CH circuit to be flushed clear. Your rads work by convection, in other words, hot water is heated by the boiler, circulated by the pump and flows into and then to the top of the radiators by convection. It then cools, drops to the bottom and out of the rad and is then circulated back to the boiler by the pump flow.

Will your process work, it may do .... will it cycle all the water out of the system and rads and therefore all the cleaner and dross, possibly not. You really want to be sure it all flushed. Only way to be sure that's happened is to fully empty the system, rads and all, refill, run a heat cycle and get all the rads up to temp and then drain again.

 

[mike42]

Thanks a lot for that !

I wonder if I made one adjustment which is to run the boiler during the process maybe that would work? (But I guess be a big waste of energy). I've put the boiler on anyway just now and closed the draw off to heat up the system. When its all hot I guess maybe I could carry on with the previous method but from what you say I'd be better off just fulling draining down and refilling again?

 

[Madrab]

Only way to be sure that the water has got everywhere is to heat it up, when it's all hot you know the water has got to it all. Then to remove all the water containing cleaner it needs a full drain down. Then it's filled again and to ensure the new clean water has got everywhere again to rinse out is to heat everything up again and then drain that down fully again. Then when you fill a third time, most if not all cleaner should be expelled and then inhibitor is added

Sorry if this means that you have spent all that time only to have to drain and refill again but didn't get to your post until now.