TR1 Posted October 23, 2022 Report Share Posted October 23, 2022 Had all rads (15) replaced 4 years ago and system power flushed to clean out sludge. Conventional convection boiler with hot water tank. For first 18 months had lots of air in rads which settled down eventually . Now noticed water is black again , system has always had inhibitor which has been topped up. System filter collects some sediment but not all. Is this all to be expected with new rads / fresh corrosion ? About to arrange another flush. Appreciate any input thanks Quote Link to comment Share on other sites More sharing options...
Walker570 Posted October 23, 2022 Report Share Posted October 23, 2022 errr orry can't help I'm afarid , my system has not been touched for 32 years at least apart from a new oil fired boiler when we moved in back then. All of our radiators seem to work along with the hot water system. Never ever gone into this flushing and cleaning thing. If it ain't broke then don't mend it was always taught. Quote Link to comment Share on other sites More sharing options...
Old Boggy Posted October 23, 2022 Report Share Posted October 23, 2022 (edited) 1 hour ago, TR1 said: Had all rads (15) replaced 4 years ago and system power flushed to clean out sludge. Conventional convection boiler with hot water tank. For first 18 months had lots of air in rads which settled down eventually . Now noticed water is black again , system has always had inhibitor which has been topped up. System filter collects some sediment but not all. Is this all to be expected with new rads / fresh corrosion ? About to arrange another flush. Appreciate any input thanks Are you still having to bleed `air` out of any rads? I say `air` as a common problem can be hydrogen evolution where either copper (pipework) or steel (rads) oxidise leaving pure hydrogen in the system, often confused with air. Back to basic chemistry H2o+Cu = CuO (copper oxide) + H2, or (FeO (ferrous oxide) + H2. This can be checked by opening a rad vent and applying a match, if hydrogen, you will get a small jet of blue flame !! Even with inhibitor, the water will not remain clear, so providing no air/hydrogen is constantly having to be bled out and you are happy with the quantity of inhibitor, then I would leave well alone. OB Edited October 23, 2022 by Old Boggy Quote Link to comment Share on other sites More sharing options...
Krico woodcock Posted October 23, 2022 Report Share Posted October 23, 2022 Black is good. Clear is bad.. Quote Link to comment Share on other sites More sharing options...
TR1 Posted October 23, 2022 Author Report Share Posted October 23, 2022 Thanks for reply, air bleeding is minimal on a couple of rads only after not being used over summer. Boiler service due in a couple of weeks so should get a measure of inhibitor level. Krico , why is clear bad Quote Link to comment Share on other sites More sharing options...
JohnfromUK Posted October 23, 2022 Report Share Posted October 23, 2022 (edited) 2 hours ago, TR1 said: Had all rads (15) replaced 4 years ago and system power flushed to clean out sludge. Conventional convection boiler with hot water tank. For first 18 months had lots of air in rads which settled down eventually . Now noticed water is black again , system has always had inhibitor which has been topped up. System filter collects some sediment but not all. Is this all to be expected with new rads / fresh corrosion ? About to arrange another flush. Appreciate any input thanks I had an all new system - new rads (24 doubles, 1 single plus 4 towel rails), new HW cylinder (direct mains pressure), new pipework and new boiler about 5 or 6 years ago. Like you, quite a lot of bleeding for many months (the system has to wind it's way around an old complex listed building passing through both loft and cellars, so lots of places for air to get trapped). Inhibitor installed from new. Magnatec filter was initially quite furry at first annual service, but was near clean when serviced a couple of weeks ago. Never been flushed as was literally ALL new when installed. Edited October 23, 2022 by JohnfromUK Quote Link to comment Share on other sites More sharing options...
B725 Posted October 23, 2022 Report Share Posted October 23, 2022 2 hours ago, Krico woodcock said: Black is good. Clear is bad.. It should be the other way round. Is the heating tank fed because it may be pumping over the open vent therfore introducing oxygen rich water, if that's the case fit a Myson airject or similar and increase the height of the open vent. As you have 15 radiators plus all the pipe work etc I would add 2 litres of inhibitor but only when the system is clean. The blacker the water the more it will cost to heat up. Quote Link to comment Share on other sites More sharing options...
TR1 Posted October 23, 2022 Author Report Share Posted October 23, 2022 About 6 litres inhibitor in system over the 4 years , tank fed with combined feed and vent. I am thinking the original flush was not carried out very thoroughly , the underfloor piping may not have been cleaned to well and it has a few dead ends from removed radiators. I also do not recall the operator do any individual radiator shut offs so whole system was open all the time. I will wait and see what water analysis show during boiler service and go from there. Quote Link to comment Share on other sites More sharing options...
B725 Posted October 23, 2022 Report Share Posted October 23, 2022 (edited) Combined feed and vent is not a good way to do, as I said fit a Myson airject or similar it's a far better way to do it, it's not expensive. The only way to power flush is by one rad at a time and the underfloor one circuit at a time, then at at the end a total system flush. Dead leg's can hold a lot of air especially if they are fairly long. Edited October 23, 2022 by B725 Quote Link to comment Share on other sites More sharing options...
Krico woodcock Posted October 24, 2022 Report Share Posted October 24, 2022 If water is still clear after 4 years, usually indicates a leak, and fresh water is coming in topping up system, therefore air, will come to system too, fresh water wil cause corrosion, through oxidation.. If it is black, blackish, means no leak. Now if there is a air dirt separator, or a manganese separator installed it will definitely curtail the blackness. I'd say leave well enough alone. Quote Link to comment Share on other sites More sharing options...
Keith RW Posted October 26, 2022 Report Share Posted October 26, 2022 +1 for the Magnatech filter system with cleaner and protectant, fitted one two years ago and thoroughly cleaned the system and radiators out one by one, filter checked and cleaned every couple of weeks during first few months after initial fitting to see water getting clearer and clearer as debris was collected by the magnets and after short period of time water from bleeding rads was clear. Will check filter again this year when central heating is eventually fired up. With regards to above post suggesting clear water would indicate a leak, I would have thought it would have to be a pretty bad leak to completely clear the system of black water held throughout the system and also at a lowest level Quote Link to comment Share on other sites More sharing options...
B725 Posted October 26, 2022 Report Share Posted October 26, 2022 My own heating system is totally clean if I've ever drained it for what ever reason I top up the Sentinal inhibitor, without seeing the OP heating I still think it's either pumping over the vent or pulling air in via the open vent , by fitting a Myson airject it allows any bubbles of air to be dispelled via the open vent. It is also possible the air is being drawn into the system via a compression joint, internal leak sealant should stop that and it can be used in conjunction with the inhibitor. The thicker and blacker the water the more it cost's to heat up the system. When the heating has been on a while if the centre bottom of the radiator is cooler than the top that is an indication of sludge build up and causes a reduction in efficiency of the radiator. Quote Link to comment Share on other sites More sharing options...
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