Fernox 56603 Leak Sealer

A decade ago we added a couple of rooms to our home which involved extending the central heating system, and at the same time replacing the old gravity fed boiler with a closed circuit pressurised system. From the outset it was apparent that we had a small leak somewhere in the system as the pressure would drop by about 0.5 Bar over a 4 to 6 week period. Checks on all the visible pipework failed to reveal any trace of leakage so my presumption has always been that the loss was occurring in the pipework somewhere under the floorboards. However, topping up the system every 1 to 2 months was no big deal and certainly less trouble than ripping up the downstairs floors. Over the last 10 years things have changed to the extent that topping up has now become a little more frequent - and this winter with the system in pretty constant use it has been every couple of weeks or so, and I had been seriously considering the prospect of having the whole thing checked out, including the underfloor pipework during the warmer weather, which would inevitably have been a major cost as well as having the house in a mess for a while.I also decided to check out if there were any other options available including treatments that could be added to central heating systems to seal minor leaks. One that came to my notice was Fernox F4 Leak Sealer and this appeared to have quite a lot of good reviews from both trade and DIY customers. So, I decided to give it a try on the basis that there was little to lose anyway.The Fernox F4 treatment is supplied in 500 ml bottles which will effective treat a system with 10 single radiators. My system is pretty big with 10 large double radiators so I used 2 bottles of the Fernox F4 added using an Eezyfill dosing funnel. I am no plumber but the process was simple enough. That was a week ago and it is already clear to me that there has been an immediate improvement in pressure retention in the system In fact the pressure has remained absolutely constant over the past week - something that has not happened at all any time during the last decade.I appreciate that this is still early days but I am absolutely delighted with the results seen so far and for an outlay of only £50 (which included the dosing funnel. I will post another review in 3 months time to give an update on things. Watch this space!My original review was made in early March and I am adding this further comment.on June 12th 2016. It is now more than 3 months since the Fernox F4 treatment was added to our central heating system. During that time the pressure has reduced slighly, from 1.4 to 1.2 bar - but even if that rate of pressure loss continues it will be at least another 8 months before I need to top up the pressure again. So, the frequency of repressurising has improved from needing to be done every couple of weeks to maybe around once a year. I can only call that an outstanding result and would strongly recommend to anyone suffering similar problems with their central heating system.I am adding this final update on November 5th 2016, more than 7 months after adding the F4 Leak Sealer to my central heating system. In those 7 months I have not had to re pressurise the system at all, and for the last 4 months the pressure has stayed absolutely constant at 1.2 Bar. Obviously the treatment has effectively sealed the leaks that were causing my original problems and I now have a watertight system which is working perfectly. Brilliant!

I had a leak on our new central heating system which was untraceable. I had to top up the pressure every week from zero. I bought this and undid and removed the top bleed valve screw on our up right towel rail in the bathroom (Highest point in system), then opened the bleed screw on the closest bedroom radiator to let enough water out to allow for the installation of the leak sealer. tightened this back up and then with a funnel poured the leak sealer carefully straight into the towel rail. once in, I then replaced the the top valve and ran the heating for about five minutes to get the sealer around the system, I then re-pressurised the system (around 2 bar) and bled the system from the highest point with the system running. Once the system was bled with no air present I re-pressurised the system again to around 2 bar (check with manufacturers recommendations for this).I completed this work around 2 months ago and have checked the system pressure periodically over this time, with no change to pressure at all. Job Done!I fully recommend this product.N.B. If your system has any additives/inhibitors in the system, check the manufacturers specifications and recommendations before using this product, as some may not be compatible with different products.Mine had Fernox inhibitor in it so I had no problems with this. if your system does not have any inhibitor added then I would recommend using Fernox Protector F1 as this is in my system and when I bled the system after 3 years of use and some old radiators too, the water was clean and clear and not black (black water is a sign of corrosion in system).All in all great products from Fernox.

I Trust it is doing the job boiler seems to retain it's pressure. I had no obvious leaks but put the stop leak in as a bit of insurance.

It has been exactly 2 weeks since I added 1 and a half bottles of F4 to my central heating system. I have waited this long in case I jinxed it by saying how good this stuff works. After 2 weeks I think we are all good. Let me explain in some detail what our issue was. We have a 1930s dormer bungalow with most of the ground floor heating pipes underneath suspended floor boards which are covered in carpet in the bedrooms and oak boards in the rest of the rooms. About 4 weeks ago our combi boiler started losing pressure requiring it to be topped up at least once a day. It was losing 0.5 Bar overnight while the system was off. That’s a lot of pressure and more than any of the other reviewers have noted in their feedback. I eliminated a cracked heat exchanger by putting a plastic bag over the condensing pipe overnight; in the morning it was still dry so it had to be a leak or leaks in the pipes under the floor. With 8 rooms downstairs this was causing me sleepless nights as where do you begin?After reading reviews on Amazon and Screwfix I ordered 2 bottles. We have 10 radiators of various sizes including 2 towel rads so not a huge system and in theory 1 bottle should have been enough but I went belt and braces. The delivery times was about 6 days with Amazon (Screwfix were out of stock). As soon as it arrived I drained about 3 or 4 litres via the outside drain tap and then added 1 and a half bottles of F4 to the upstairs bathroom towel radiator. I repressurised the system to 1.5 Bar (top edge of the green zone on the boiler pressure gauge) and then turned the heating on. I made sketches and took photos of the gauge so I could then monitor the situation. Every morning I would check the gauge and pray the pressure had not dropped. I am delighted to say it didn’t, so wherever that leak was, and maybe there were several, it has been sealed by the F4.For about £20 a bottle it is the best money I have spent in a long time. I am still slightly nervous in the long term so will give an update in several months but if you have a leak in your pipes this stuff should work.