Megaflow - not enough hot water

[affe]

I have a Megaflow system which is about five years old. It works fine except that the amount of hot water available is less than two showers' worth. It's been like this for ages (only just getting around to sorting it!), when we first moved here I'm sure we had visitors and four showers was no problem. The tank is a CL210.
I've done the refill procedure which hasn't made a difference.
Any advice appreciated.

 

[Puddle]

Hi affe

Is it heated by a gas boiler or electrically by immersion heaters

 

[PLUMB111]

Give us more info and we may be able to help.

 

[affe]

Hi,
Sorry for the slow reply, back online now.
Heat comes from a Wallstar oil fired boiler.
Seems to work just fine although I have noticed it sometimes runs when the timer is off (off for both heating & hot water), which seems strange as I thought it could only run when the timer made "call for heat" live.
Anyway, not sure that's related to the lack of HW from the cylinder.
Regards,
Affe.

 

[Puddle]

Only asked if heated by immersion heaters as posible one faulty
However if heated by boiler this is not the case
The first thing to check is that the cylinder thermostat has not been turned down by mistake causing only half tank to be heated,maybe it has always been set to low and at first you had immersion heater on also,now turned off
Likewise check boiler thermostat is turned up correctly
Check you have no badly dripping taps,no taps left on slightly,went to one house with this problem and a down stairs clockroom tap had been left on slightly for previous two weeks as no one usually used room :.)

 

[affe]

Hmmm, didn't know the cylinder stat could be altered, will have a look.
Immersion defo. been off the whole time...I have paranoia about immersion heaters & the resulting leccy bill!
Checked boiler stat and is on max.
Taps all off.
A thing that seems odd is that sometimes when the boiler is on there's a serious gurgling sound. Kind of like water being heated against a closed valve, but that's a total guess. Also, should it be possible to generate a gurgle if there's no air in the system? Maybe totally unrelated.
Will come back on the cylinder stat question. Many thanks for the help so far; appreciated.