Hot water overflow from F&E tank

Discussion in 'Plumbers' Talk' started by MikityP, Dec 17, 2019.

  1. MikityP

    MikityP New Member

    Thanks Severntrent, I really appreciate the reply. I will certainly try changing the pump up to the full setting before going to bed tonight and see what happens tomorrow morning.

    I noticed a slight hissing from the bathroom radiator and I fiddled with the valves and a small amount of air seemed to be released, but I doubt if it would be enough to be causing the problem.

    Hope you have a good rest of your boxing day!
     
  2. MikityP

    MikityP New Member

    Happy New Year to everyone.

    OK, here's the latest development in our problem. This morning, we were woken up by hot water gushing into the F&E tank again. However, this time, the pump was on the lowest possible setting (fixed speed 1). Having given it some thought, I am not convinced that this is an overheating situation. One reason for this is that the pump was still going after the overheat switch had been tripped on the boiler. So, I am guessing that the water in the hot water cylinder had not reached the required temperature to switch it off. Also, having turned them up and down at various times, both of the thermostats on the hot water cylinder and the boiler seem to be working OK.

    I am wondering whether the problem is caused by air in the system that isn't venting properly or possibly we are getting more air in our system somehow? However, could air in the system cause these problems? I am thinking it might be air because when you look at the hot water from the taps through a transparent jug there are tons of bubbles in it which are not present in the cold water. Also, the taps tend to splutter when hot water is requested. You can also here a gushing noise through the pump which I thought was a sign of air in the system (the noise gets worse when the pump speed is increased). Lastly, when I was up early a few days ago and the hot water was on in the morning, I heard a popping noise from the hot water cylinder which sounded like trapped air to me.

    We have now called a professional plumber out, who hopefully will be able to come round soon. However, if anyone can think of something we could try in the meantime, that would be great. As the problem only occurs in the morning, we have just switched the hot water off at this time, but I would guess we may start to get problems at other times of the day soon.
     
  3. Severntrent

    Severntrent Screwfix Select

    Intriguing, please keep us updated. Have googled around several forums on *** cutting out and it would appear that its a problem that has been going on for years but no one has ever come up with a definitive answer. As for all this air within your system its a chicken and egg situation, does the air come about due to the high temperature within the boiler (bit like a kettle) or does the air (from some other source????) cause the high temperature of the boiler. Since the boilers seem to work OK originally I'm leaning towards some control function in the boiler being amiss. I'll see what the summer brings around and since my boiler is approx. 25 years old perhaps go for a new one.
     
  4. MikityP

    MikityP New Member

    Thanks. I must admit I hadn't thought it would be a boiler issue :( I will see what the plumber says and let you know what happens!
     
  5. Tricky Dicky

    Tricky Dicky Screwfix Select

    Welcome to 2020,
    My father had similar problems to you, although a different boiler, just a few suggestions, increase the height of the F and E expansion pipe in the loft (what does the boiler manual suggest), do you need a boiler by-pass pipe, perhaps an automatic valve; https://www.screwfix.com/p/honeywell-straight-auto-bypass-valve-22mm/34127 ; finally regarding the TRVs on your rads, leave 2 or 3 rads with no TRVs eg bathroom, hall or landing. Removing 3 TRVs on my fathers central heating finally resolved the problems(s). No more overheating or boiler tripping out or F and E pipe 'pumping' into the tank.
    Best of luck.
     
  6. Severntrent

    Severntrent Screwfix Select

    How is it when you put 2 F and an S together they are replaced with 2 asterix
     
  7. Severntrent

    Severntrent Screwfix Select

    Checked the air vent pipe a little earlier today and this was indeed over pumping even at low pump setting so next task is to raise it, 450mm above the TWL in the expansion tank seems to be the norm but as mine is thereabouts anyway I'll raise it another 300mm. Also have read that this over pumping causes excessive air entrainment into F&E tankwater with subsequent issues with corrosion , I should think that this may also cause excessive air being introduced into the system via cavitation at the pump which may lead to boiler cut out issues although radiators do not seem to need any bleeding. Just for fun yesterday I took apart the old pump I replaced a few weeks ago and the amount of gunge locate within, and restricting, the impellor flow ways has converted me to a Magnaclean advocate so that's another task to sort. Hallway and bathroom radiators don't have TRVs so will make sure valves and lock valves are fully open and may take TRV off one other radiator and see what transpires. Life's a challange:(
     
  8. MikityP

    MikityP New Member

    OK, I just thought I would provide you with an update. Our plumber came round and said that he thought that our boiler and hot water thermostats were set too high (despite the fact they were on their recommended settings for winter). He thought the boiler thermistor was probably gunked up and detecting the wrong temperature and the hot water cylinder thermostat was towards the bottom of the tank and therefore should be on a lower setting in order not to unnecessarily overheat the hot water. Well, this approach seems to have worked... We have had no overheating issues in a month.

    However, I don't think things are perfect. The plumber has recommended a power flush to clean the system out, but we don't have any of the signs that we require one. Our radiators don't have cold spots and the water from the central heating system was pretty clear last time I drained it down. Also, we still have tons of bubbles in our hot water whenever we turn a hot water tap on, which doesn't seem normal to me. However, as long as the system isn't overheating, I'm happy :)
     
    Severntrent likes this.

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