Yes! Usually, I set it to heat for 1 hour a day in the evening. But since this started I turned the program off, and I've heating it just for a 20-30 minutes a day, enough to have a quick shower before the tank fills too much with the mains open.
Exactly.or a pin hole. If the pumps electrically isolated and water level continues to rise ,it can't possibly be the pump.
It’s possible but unlikely. I’m not sure if it has a built in filling loop. Most older system boilers didn’t.
Are you sure no other mixers are fed cold water from mains ? Turn main stopcock off ,and run all cold outlets ,if cold water still comes out they are tank fed. Can you also please take pics of pipework around boiler , would like to see if there is an external filling loop.
Someone could have tried to fit an outside tap with both a hot and cold with isolation valves. Maybe the cold is turned on but the hot passing. Sometimes diy plumbing throws up allsorts. Not seen allsorts in a while on here.
It just seems like there’s a water main connected to the hot somehow. Your water level wants to reach higher than tank level. It can only be caused by a pump or water main.
@terrymac & @Mike83, here's the tap situation, I filmed it in 2 different scenarios - always with pump off, and cold water tank with water. Mains Off: Mains On: ^ weirdly the bathtub tap seems to have water once opened in the cold, but switching to hot and back made the flow a lot lower. I tried to take a picture of the boiler pipes, but someone had a great idea of making it very hard to remove the board with some kind of sealant, does this helps at all:
I left the bathroom tap open for a few minutes (with mains off) and it went dry. But it's definitely fed by the pump because it kicks the pump in when open and I can see the pressure.
Basin tap is a bit suspect ,if its cold position runs dry with mains off ,it would be indicative that its not tank fed ,unless the loft tank was short of water. There was definitely more flow when mains was put on at the basin tap ,but I would have expected it to be even greater, unless there is a valve under the basin that's part closed. Can you take pics of pipes under basin ( looking for valves like you took pics of under kitchen sink). Boiler pics don't show much ,but I can see a silver braided flexible hose ,which is likely the filling loop, one end is visible. Can you follow that flexi and take pic of the other end of it ,which should have a lever valve.
Thanks @terrymac, So for the boiler part, I think these are the 2 ends: Then for the sink, it's quite hard to get a closer look. The same sealant between the tiles was applied to the "removable" plate of it. This is what I could reach, and with a zoom: But this is all protected by this, do you think it will come off if I unscrew it?
Also, the insurance is sending a boiler engineer tomorrow, is there anything technical I could tell him to look for? I'm going to mention the loop thing, probably see if he would be kind enough to read through this thread haha.
Thanks ,the isolators to basin taps look OK ,full on. The braided hose is your filling loop ,if you look closely you will see a black plastic lever at the end.Its that lever that you turn ,only a quarter turn ,to let water into boiler to top up pressure to 1 bar. When 1 bar is reached ,make sure you fully close the valve. Hopefully your engineer will suss out tomorrow what's going on ,and I doubt he will want to read all this thread ,he can establish on site far more than we can with a few pics. Here is what you should tell him as facts established by yoiu.... 1. The loft tanks water level rises to overflowing ,despite the ball valve not letting water in. 2. You have seen water coming into the tank from the tank outlet( cold feed to hot water cylinder),and this happens when shower pump is electrically isolated ,and boiler is off. 3. When water mains is closed at stopcock ,water no longer back fills the loft tank. 4. The boiler pressure gauge is zero. Then its down to him ( or her)
Ok... So here's what he said. He believes some pipe inside the hot water tank is broken, and because of that the pressure is down and the water is going backward. He sees 2 solutions: A) replace the whole thing with a combi boiler B) replace the hot tank, but according to him the pressure changes of doing this will also require changing the boiler because it's old. I'm slightly suspicious as he said he could indicate to me someone for the boiler work. Having a combi boiler would be a dream, but there was a report years ago that I didn't have enough gas pressure... he said I could replace the gas hob with an electric one to help with that. So, nothing is solved, still in despair
If the pipe inside the water tank was faulty your pressure on the boiler would constantly need topped up unless the filling loop was passing. If the filling loop was passing then I would expect the pressure gauge to be reading a bit higher than it’s showing.