Fallingditch Posted February 21, 2017 Share Posted February 21, 2017 Old edwardianl house with a forty year old central heating system. Modern Vaillant combi boiler that has to be regularly repressurised with mains water. This suggests a weeping joint in the system somewhere - but there us no visible evidence - may well be under the ground floor floorboards (or elsewhere). What is the best approach to finding the source of the leak? Are there any tools available whch I could hire for instance? Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 22, 2017 Share Posted February 22, 2017 Sentinel Leak Sealer is what you want. . Very good stuff and works lightning fast. Dose and run the heating for an hour as hot as you can get it, then after the leak is cured, drain and top up the inhibitor. Link to comment Share on other sites More sharing options...
Alexphd1 Posted February 22, 2017 Share Posted February 22, 2017 First off check the prv. If you do use leak sealer when you dose/add it to the system make sure that system is cold (radiators and not running hother water)..... don't ask me how I know this?? Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 22, 2017 Share Posted February 22, 2017 11 minutes ago, Alexphd1 said: First off check the prv. I assumed this would have been eliminated ?. Good point ? When the combi was fitted, did they fit new rad valves to BOTH sides of EVERY rad? How many radiators? Link to comment Share on other sites More sharing options...
Fallingditch Posted February 22, 2017 Author Share Posted February 22, 2017 9 hours ago, Nickfromwales said: I assumed this would have been eliminated ?. Good point ? When the combi was fitted, did they fit new rad valves to BOTH sides of EVERY rad? How many radiators? PRV - is that Pressure Relief valve on the boiler? System was installed way before present occupiers moved in Fifteen radiators on three storeys. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 22, 2017 Share Posted February 22, 2017 2 hours ago, Fallingditch said: PRV - is that Pressure Relief valve on the boiler? Yes. It's common for the PRV to fail and 'let by'. Water comes out of the copper overflow pipe at the rear of the boiler ( outside wall ), but can be tricky to catch as it often will do it when the system is hot and it evaporates away. Zip tying a clear bag over the end and making sure rain doesn't get in is the best way to see if it's been discharging. 2 hours ago, Fallingditch said: Fifteen radiators on three storeys. This could be the problem. An average system is around 10 radiators. It may be that the system doesn't have sufficient expansion and is causing the PRV to open. The boiler gets topped up to say 1bar, then the system heats up. The high volume of system water expands beyond the capacity of the boilers expansion vessel ( EV ) and the PRV opens to relive the excess pressure. The system then cools down again, when the heating turns off, and the water contacts. As there is water missing, the system pressure drops below the low pressure threshold and the boiler goes into lockout with low pressure fault on the display. How often are you having to top up, and how long has this been a problem ? Do you know if there is an additional EV? Link to comment Share on other sites More sharing options...
drliamski Posted February 25, 2017 Share Posted February 25, 2017 Hi all, I am the present occupier! Thanks for your help Nick + Alexphd1 Boiler is a Vaillant ecoTEC plus 937. Afaik there has not been instance of overpressurising it and forcing PRV to relieve pressure, more of a slow drop over a few weeks until low pressure fault. I will test the prv valve using a bag over outlet. Leak has been there since before the new boiler fitted. We have an issue with one bathroom rad (1st floor) not warming up. I have removed valves and no hw or return eitherside of TRV or lock? Feed + return pipes are dry. Think there is a possible blockage specifically on this loop? Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2017 Share Posted February 25, 2017 If the pipes are dry then they're disconnected. There's no way a blockage would be tight to 1 bar on BOTH pipes It may well be that this was the old heat leak rad that was plumbed in parallel to the hot water cylinder so, worst case, will need to be teed back into the flow and return. Is there a magnetic filter at the new boiler location? Oh, and don't forget to make sure rain can't fill the clear bag Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2017 Share Posted February 25, 2017 And welcome to the mad house ! Link to comment Share on other sites More sharing options...
drliamski Posted February 25, 2017 Share Posted February 25, 2017 49 minutes ago, Nickfromwales said: If the pipes are dry then they're disconnected. There's no way a blockage would be tight to 1 bar on BOTH pipes It may well be that this was the old heat leak rad that was plumbed in parallel to the hot water cylinder so, worst case, will need to be teed back into the flow and return. Is there a magnetic filter at the new boiler location? Oh, and don't forget to make sure rain can't fill the clear bag That is what I feared, two plumbers have suggested powerflushing but I am not convinced, should be relatively easy to get access to flow and return in cupboard next door. Yes there is a magnaclean filter. I have not checked it though. I will seal bag well! Thanks for the welcome! L Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2017 Share Posted February 25, 2017 I only ask about the filter as it's a 5 min job to dose with Sentinel with one of those ? Eliminate the PRV and come back to us re the leak sealer . Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 25, 2017 Share Posted February 25, 2017 My experience with having a Vaillant Ecotec fitted as a replacement for a ~30 year old system boiler was that power flushing was needed as part of the installation, in order to get the full warranty (at least that's what we were told). We did have the whole system power flushed and I was absolutely staggered at the amount of crud that came out. The magnetic filter in the power flush unit had to be cleaned off at least three times during the couple of hours or so it took to flush the system, and as far as I know the system had always had inhibitor in, as we inherited half a big can of Fernox when we bought the house and there was a Fernox tag on the old header tank. I can say that power flushing does work, though, as every year there's barely anything on the Magnaclean filter magnet now. As above, I can't see how it could just be crud causing a rad to be dry, it sounds very much as if it's disconnected to me, as Nick says. I've experienced a completely blocked rad, with a couple of inches of crud in the bottom, and even that was flowing a tiny bit of water, it just wasn't getting hot. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2017 Share Posted February 25, 2017 I think the mention of power flushing as a routine part of a new installation, and power flushing as a resolve to a blocked pipe need separating out. Paying someone to PF dry pipes won't do a thing so would, afaic, be a waste of money, time and effort. When retrofitting a new boiler to old pipes and worse, old rads, a PF is mandatory in most cases. Bump : Are the rad valves ALL new? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 25, 2017 Share Posted February 25, 2017 12 minutes ago, Nickfromwales said: I think the mention of power flushing as a routine part of a new installation, and power flushing as a resolve to a blocked pipe need separating out. Paying someone to PF dry pipes won't do a thing so would, afaic, be a waste of money, time and effort. When retrofitting a new boiler to old pipes and worse, old rads, a PF is mandatory in most cases. Bump : Are the rad valves ALL new? I'd agree, but raised it only because there was no mention of a power flush being done as a part of the new Ecotec install, and I was led to believe that Vaillant would only give their extended warranty if this was done, as well as a magnetic filter being fitted in the return. If the system had been power flushed when the new Ecotec was fitted, then it seems very unlikely that doing another one would achieve anything. Link to comment Share on other sites More sharing options...
drliamski Posted February 25, 2017 Share Posted February 25, 2017 20 minutes ago, Nickfromwales said: Bump : Are the rad valves ALL new? All relatively new as are all Honeywell TRV. Dont know how new. Some of the lockshields are definitely old! Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2017 Share Posted February 25, 2017 With 15 rads and a new sealed and pressurised system, it begs belief that they left the original rad valves on. What usually happens is the o-rings / other seal on the valve stem ( bit that turns ) go brittle and allow small amounts of water to escape. They're very difficult to diagnose as there is usually little or no visible evidence of them leaking. The reason for that is when cold they seal, but when warm / hot, the metal expands slightly and relaxes its grip on the stem seal. That allows water to leak very slightly into the valve head, but it then simply evaporates as it does so, so no tell tale drips on the floor. Multiply that by 15 and it's game over. Taking the heads off the lockshield valves may show evidence e.g. corrosion and green oxide sat around the valve stem. I'd bet that this is either the cause, or very much a big part of the pressure dropping. This can be easily solved with leak sealer, but only on the understanding that you can never turn these valves again ( or you'll break down the leak seal that's formed there ). A bit like the old 'chucking an egg in the car radiator' trick. Can you check all the LS valves? They should click off or have a screw in the centre. DONT LOSE THE SCREWS ! Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 25, 2017 Share Posted February 25, 2017 Nick, isn't changing all the rad valves also something Vaillant ask for when a boiler is fitted to an existing installation? I know that it was called for on ours, and I agreed that I'd supply and fit new valves and TRVs whilst the fitters had the system drained down (which was overnight, as they had to rip out the old system boiler, tank, cold tank, header tank and a lot of the loft plumbing). Again, I was told, rightly or wrongly, that the Vaillant extended warranty depended on this. IIRC, the three things that were essential to get the longer warranty were a power flush before commissioning, the fitting of a magnetic filter on the return, as close to the boiler as practicable and the fitment of new rad valves, including TRVs. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2017 Share Posted February 25, 2017 I'm not so sure about having to change ALL the rad valves, but it IS in the benchmark certificate that TRV's a room stat ( temp controls ) are fitted accordingly with one rad always being left without a TRV for system bypass. I always do that one by the front door / entrance hall as the uncontrolled heat soon disappears upstairs. Plus you need a rad on bypass to service the air space where the room stat is located so it always has a reference temp available. Changing the LS's isn't mandatory afaik, but not changing them is just bad practice imo as a system that's only ever seen a bit of gravity pressure will soon start leaking when you get to 1.5 - 2 bar operating pressure. Combine that with the flow from a new 6m head pump and you get to where we are here . Leakville, Tennessee. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 25, 2017 Share Posted February 25, 2017 Thanks Nick. I replaced all the valves, fitted TRVs to all the rads at the same time (they didn't have them before) and installed a big heated towel rail in the bathroom, in place of a small rad, with no TRV. The installers power flushed the system and fitted a Magnaclean as a part of the install. The installers were fine with this, but that's not really saying much, as they turned out to be a right shambles when it came to fixing constant, recurring, faults with the boiler...................... Link to comment Share on other sites More sharing options...
joe90 Posted February 25, 2017 Share Posted February 25, 2017 Well I had to call out my tame British Gas engineer ( a mate) for a fault and he said standard British Gas policy is to recommend a power flush on systems more than a few years old, however, he finds that fitting a magnaclean and switching of all radiators but one ( at a time) and running the heating on full chat for an hour per radiator and cleaning the magnaclean after every radiator does just as well without the cost and potential mess from a power flush. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2017 Share Posted February 25, 2017 13 minutes ago, joe90 said: he finds that fitting a magnaclean and switching of all radiators but one ( at a time) and running the heating on full chat for an hour per radiator and cleaning the magnaclean after every radiator does just as well without the cost and potential mess from a power flush. That's stretching the imagination a bit too far there im afraid. ? A 2hp pump blasting through the pipework is chalk and cheese to the boiler pump doing it, plus, the PF machine is flow reversible so you get to send water through in the opposite direction to lift more debris out. The magnetic filter soon becomes saturated and overwhelmed by crud, so some of it has to go back in. With a PF machine you have a clear vessel so you keep flushing and reversing, emptying and refilling until the water is clear. That takes all day in some jobs as PF'ing isn't quick and easy by any means if your going to be thourough. . Checking and cleaning the magnetic filter every 3 months in the first year is good practice, but a proper PF is in a league of its own. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 25, 2017 Share Posted February 25, 2017 Having seen this done, I'm 100% with Nick on this! The power flush tank our guys used was around a 2ft cube of translucent plastic, with a massive pump and a magnetic filter around 5 or 6 times the size of the one in a Magnaclean. The flow rate when on full blast was more like a pressure washer than a circulating pump. The guys did say that one risk was that old steel radiators might develop leaks afterwards, from pinhole corrosion that was exposed by the crud and scale being blasted away, which gives some idea of the flow rate. It's a pretty noisy beast when running, with the flow noise very audible in all the rads as they were being flushed. 1 Link to comment Share on other sites More sharing options...
joe90 Posted February 25, 2017 Share Posted February 25, 2017 ? 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2017 Share Posted February 25, 2017 1 hour ago, joe90 said: ? Your a big boy now Joe. Wipe those tears away and come for a cŵtch cariad. Link to comment Share on other sites More sharing options...
joe90 Posted February 25, 2017 Share Posted February 25, 2017 (edited) It appears I misunderstood my Gas Board mate ? I called him for clarification . He confirmed that for a blockage or old system with flow problems then a power flush is the best way forward ( with a caveat that weaknesses might turn into leaks) but in his personal opinion ( 35 years with the Gas board) systems such as mine that are a few years old and not suffering from flow problems then installing a magna clean and turning the pump up and forcing the flow through each radiator in turn and cleaning the magna clean after each radiator is sufficient. But he is instructed by his employer to actively sell power flushes.. Edited February 25, 2017 by joe90 Typo Link to comment Share on other sites More sharing options...
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