CH not reaching desired temperature

15 Jan 2016
Reaction score
United Kingdom
I'm after a bit of advise. I couldn't find anything relating to this specific query, apologies in advance if this description is a bit vague..

First thing first a confession, my stupidity originally may (or may not) have caused this. We moved into our new (first) house and in a flurry to find the water stopcock, my girlfriend and I opened any valves/gates we could get our hands on :rolleyes:
I cant be sure, but I can't rule out that the valves in the airing cupboard were opened at this point, as all 3 are fully open currently.

Since moving in, the temperature has felt cold, and never reaching what the room thermostat is set to - 21 degrees. Depending on the room, it is reaching 11-14 before the boiler switching itself off for anywhere between 10 mins and half hour or so. (It is a new Glow-worm Flexicom 15hx, fitted about 3 months ago when the previous owner was here). There is only one setting on the front. It is set to 65 degrees. It seems to reach this temperature according to the display, and that it when it turns off.

After doing some research on the issue, I inadvertently read that when a bypass valve (manual gate) is fully open, the symptoms above would be observed and the rooms would never reach desired temperature.

Could I be right in saying I need to do the gate up (open around half a turn) to get the water flowing through the rads correctly - or am I barking up the wrong tree completely?
The radiators do get semi-hot, but the rooms never get to where they need to be.
I have attempted to balance the radiators which has made the furthest away rads feel marginally better, but the overall room temp hasn't increased much.

Image attached is the airing cupboard, and I assume if I am correct that the bottom most gate would be the bypass? If so then this is currently open.

Thank you all in advance!


  • IMG_6895.JPG
    99.9 KB · Views: 240
Sponsored Links
Thanks for replying. Is that the one at the bottom do you mean? Top (red) one feeds into the tank.
Sponsored Links
I'm afraid not.. had it on for 2.5 hours or so and still hasn't made its way above 14/15 degrees.
The rads are reasonably warm but not scolding.
Professionals rules of fault finding by the way:

  1. Is it turned on?
  2. Are you sure it's turned on?
  3. Is it really turned on?
  4. Should it be turned on?
  5. Can you turn it off if you turn it on?
Blimey what a mess (the plumbing). difficult to say from the pics, btu that gate valve might well even be for the hot water.

Turn it back on and try the one down the bottom (behind the loop of black wire). Same thing - fully closed then back half a turn.

I'd be setting a some money aside to have that lot upgraded too -

pump is pumping down - bad
no temperature control apparent on the hot water - bad
general state of plumbing - abortion.

Worrying presence of part of a push fit fitting on top of the cylinder.

If this is your first place, and you don't have a handy relative that knows his or her way around the mechanics of a house, it might pay you to get a pro in anyway to give the boiler a once over and show you where things are.
Thanks Dan, Yes we've inherited a beaut there.
I tried tightening both individually, but didn't seem to have any impact on the boiler powering down. It seems to fire up, reach 'desired temperature' within 5 minutes or so, then power down until the temp falls to about 49, then starts the cycle again.
No errors at all, and status codes look normal when its doing its thing.
It just never seems to get above 15 or so on the thermostat, even when turned up high. Radiators get warm/hot then fade periodically.

As for the pump, the arrow is facing down which is the correct direction of flow I guess from the writing. As for whether this is in the flow direction from the boiler I do not know.

The shower has been connected with push fit joints, hence the extra one on top of the tank!
Time to admit defeat and get someone in!
Do the symptoms sound indicative of somebody messing with the valve? If so then it'll teach me.
Is this something which should be relatively easy to iron out?
That red cylinder jacket is not needed - it's covering a foam lagged cylinder:whistle:

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links