I recently drained my friends combi boiler added some sludge remover, then eventually put some inhibitor into the system, for the first couple of weeks my friends was really pleased as he noticed that the boiler was quiter, however he is not noticing that when he puts the hot water on there is brown water that initailly comes out, he is positive this has only started since the system was drained.
Any ideas what could possibly be doing this.
BTW, sludge remover and inhibitor fed into the system via radiator.
A leak in a heating coil somewhere inside the system causing water from the boiler/radiator part of the system to get into the hot water part of it. The sludge remover probably removed sludge that was actually sealing the pinhole. Very common in the coils inside immersion tanks as they corrode internally.
-- "I found this stone in the park yesterday. It's been worn to a perfect sphere by the elements and dimpled by time." "Harry, that's a golfball!" (3rd Rock From The Sun)
In a combi this would be a leak in the secondary heat exchanger. This is where water from the primary circuit (ie the stuff that goes through the radiators) "meets" the domestic hot water that comes out of the taps. In fact that they shouldn't quite meet, they should just get close enough either side of a piece of thin metal for the heat to pass from one to the other.
However, as Dave says, it may be that the sludge remover was a bit too aggressive and has corroded the metal of the heat exchanger allowing water from the primary circuit into the DHW. This would lead to a loss of pressure in the primary circuit as water seeped out. Is your friend having to top the boiler up using the filling loop?
If the heat exchanger was in that state and the system was sludged up anyway I wouldn't feel too bad about it - the heat exhanger would have needed replacing soon. If it does need replacing it should be done as a matter of urgency. You don't want to be doing your washing up in water from the rads, and constantly topping up the primary circuit means that the corrosion inhibitor is being diluted and the system is likely to suffer from more sludge and corrosion.
replying to Martin Pentreath, eggheadstevens wrote: It would actually increase the pressure in the heating system causing it to escape out the pressure relief if the in coming mains as would be expected be greater than 3 bar
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