Having more problems with CH/HW and wonder if there's any advice (it
really would be appreciated as I'm rapidly losing hair!)
Two weeks ago I filled my central heating system with Salamander
FastCleanse cleaning agent. Yesterday, I drained the system and flushed
it for an hour or so from the header tank, and that's when the problems
started. I now cannot get the upstairs rads to refill. I also noticed
this morning, that the hot water is only warm.
Now, my system is a Baxi Bermuda where the boiler is behind the
fireplace, and the hot water needs to be on in order for the C/H to be
on. The downstairs rads are steaming hot (I assume because there is no
circulation to upstairs)
Anyone any ideas why my upstairs rads won't fill up? I thought they
would fill from directly from the header. Does this indicate a blockage?
If so, how do I find/clear it? Also, why would I be out of H/W?
Any advice would be greatly welcomed.
Thanks for reading
Almost certainly an airlock. Common way round is to connect a mains water
pressure hose to the drain point and force water into the system that way.
Have someone keep an eye on the header tank and make sure it doesn't
*It's lonely at the top, but you eat better.
Dave Plowman email@example.com London SW
if it ain't broke, don't fix it ?
seriously, it sounds like you've dislodged some chunks of sludge wheich have
blocked either a flow pipe or a return. you could try a proper powerflush to
clear any blockage but you may ahve to resort to dropping various rads off.
Have you bled the upstairs rads? If not, do so.
Is the header tank at the correct level?
Is the pump working? If yes then try turning off all downstairs rads,
what happens to the upstairs rads now, do they get warm? If not
systematically turn off all rads upstairs except one.
Once you overcome these problems you will probably get a huge gurgling
noise resonating around the system and the problem will sort itself
I doubt it will be a piece of smeg which has gunged up the system, more
likely an airlock.
Thanks for the replies guys, I wondered if it was a blockage. The reason
I did it was because the flow was week upstairs, so I gave the treatment
a go before forking out 300 quid on a power flush.
Incidentally, how has this stopped the H/W working? There are no hot
pipes into the H/W tank at all...
Many thanks again for the assistance.
The treatment won't have done any harm but I suspect the reason why the
flow is weak upstairs is because the system requires balancing (see FAQ
Don't fork out on a powerflush, there is no way the upstairs radiators
will be blocked and the downstairs not, so this is surely not the root
of the problem. You would be getting triagular cold patches in all
radiators most likely, if this were the case.
You must have SOME pipes into the HW tank surely! How would water get
in/out for a start! Odds are there'll be a bleed valve of some sort at
the high point, this will allow air out of the HW loop. Try forcing the
air round first by turning off the rads, (followed by repeated bleeding
of air from rads). This will at least confirm the airlock theory.
I presume that you mean that there *are* pipes but they are not hot - rather
than the pipes not existing?
I imagine that you've got 4 water pipes connected to the boiler. Two will be
28mm and will connect to the indirect coil in the hot water cylinder. When
everything is working properly, water will circulate by gravity (convection)
through these pipes and heat the hot water. The other 2 pipes (22mm) will go
to the radiators - and will probably split into an upstairs and downstairs
circuit after the pump. The fill and expansion tank is probably connected to
the gravity circulation pipes in the airing cupboard.
Filling such a system can be a bit tricky - because the water has to take a
tortuous route to get everywhere - particularly to the upstairs radiators.
As others have said, you've almost certainly got airlocks both in the
gravity circuit and in the upstairs heating circuit. Filling from the bottom
by *gently* introducing mains water in through the drain cock will often
If, when you've done this, you're still having problems with the upstairs
radiators, bleed quite a lot of water (couple of litres at a time) out of
each rad - first with one valve open and the other closed, and then vice
versa - to ensure that you bleed *both* supply pipes.
Thanks for the reply. I did as Luke suggested and switched off the rads
downstairs. I got a bit of gurgling in the pipes, then all upstairs rads
seemed to bleed (water eventually came out of the bleed hole, but the
rads aren't as hot as I expected.) Anyway, there are still no hot pipes
near the hot water tank. Should I therefore try the bottom fill method?
I'm just concerned that now the rads are full, and C/H header tank is
full, I'll end up just pushing water out of the overflow.
Forgive my ignorance, I just want my hot water back :(
Thanks again for taking the time to help DIY newbies like myself, I for
one appreciate it a great deal, and would be lost without these groups!
Do you definitely have no bleed tap anywhere near the HW cylinder? It
might well look a bit like this:
Whatever it looks like it will be at a high point and connected to the
HW coil in the cylinder as opposed to the cold in/hot out connections.
On one like this you undo the top and air comes out.
Regarding the fact that your upstairs radiators are still reluctant to
get hot, despite bleeding, I reckon it's a question of balancing the
Regarding the bottom fill method if you do go down this route, you can
either keep filling until the tank overflows or drain down and start
again. Remember to add inhibitor when the job's done. I'd use this is a
last resort though. You might still end up with air in the HW circuit
because there is no easy way to force the air around.
Thanks, I'll have a root around the airing cupboard.
I think you're right. I switched all except one upstairs radiator off,
and it got hot. Did this with each radiator, and all responded in the
same way. I've found the guide in the FAQ so I'll have a go over the
Typical!! I could live without hot radiators (don't let my missus read
this!) Just the hot water I can't!
Thanks again for your assistance, Luke, and all.
Have you got an immersion heater in the tank which could heat the water in
the short term until you've sorted the circulation?
Where do the fill and vent pipes from the fill & expansion tank join the
other pipework? With gravity systems, it is common for these to be connected
to the HW circulation pipes close to the cylinder - in which case the air
should escape up the vent pipe. But maybe yours is not like that in which
case there should be an air vent at the highest point - or even higher,
using a little stack pipe - of the gravity circuit.
Hi Set Square,
The pipes from the fill/expansion tank do indeed join at the cylinder
heater. The other side of the cylinder heater also goes up to a vent
pipe. Would this not indicate that air *should* get out of the system on
Just a thought...and shoot me if I'm being stupid...could I feed a hose
into the vent pipe, and fill the water heater pipework up that way? I'm
assuming the water would all join back up at the boiler?
I doubt whether that would work - the water would probably flow through the
coil in the hot cylinder, and back up the fill pipe. You really need to fill
from the bottom, to push the air upwards.
Where do the pipes run between the boiler and airing cupboard - are they
more or less straight up and down, or do they cover a significant horizontal
distance? If the latter, could there be a dip part-way along the horizontal
section which could trap air?
Ok, tried filling from the bottom (incidentally, it's a drain point
inline with the pump, is this normal?) Bu couldn't seem to get any water
in. I switched all rads off and blocked the outlet of the header tank in
the hope water would eventually flow out of the vent pipe of the coil.
No such luck. In fact, I'm not sure if any water actually went into the
system. Am I better off draining and starting again?
There's a 9-ish foot vertical out of the boiler and up the side of the
chimney breast, then about 10 feet horizontal to the tank. I guess it's
time to get the floor boards up to check for dips.
Incidentally, something you'd mentioned before about pipe sizes, there
are 4 pipes coming out of the boiler, as you said, but they're all 22mm.
There doesn't seem to be any 28mm ones. Of these one is untouchably
hot (C/H flow?) one is cooler but still quite hot (C/H return?) and the
other two or just mildly warm (and are the outermost two pipes of the 4,
if this helps anything!)
Thanks again for your advice.
Silly question - you did actually *open* the drain cock?
It seems to be going that way!
It might be a good idea. Whether you'll be able to do anything about it is
another matter! If the pipes run between the joists - rather than across
them - and are not supported, they may sag in the middle - and supporting
them may help.
That is not good news! Gravity circulation really *needs* 28mm pipes - and
is not likely to work very well with anything less. I think that, in your
position, I'd be looking seriously either at installing a second pump or at
re-arranging the pipework to provide a fully pumped system with a single
Yes, but not enough it seems. Tried again opening drain cock fully and
water can now be fed into the system, eventually coming out of the vent
pipe. I've temporarily blocked the vent pipe too, so as to force water
round everywhere. I eventually got the inlet to the coil hot. However,
it doesn't stay hot, and the outlet from the coil doesn't seem to get
very warm. Could this indicate a blockage in the coil?
It never rains but it pours!! The hot water was always fine before I
drained the system. As I'm hoping to move in the near future, I don't
think I want to start forking out for a new system unless I really need
to. Of course, I'm totally grateful for the advice you are offering.
Doubt it. There must have been *some* flow through the gravity circuit -
otherwise hot water wouldn't have travelled to the inlet. The water coming
out of the outlet *will* be cool until the water inside the tank has heated
up. How long did you leave it running for? There could still be a partial
airlock which is slowing down the flow - but as long as there's *some* flow
it should eventually clear, and things should return to normal.
Thanks again Set Square. Right, I might just be flapping over nothing
now, but I have noticed the thermostat for the hot water doesn't appear
to be clicking in, but I don't know why not! Are there separate
thermostats for CH circuit and HW circuit? If I turn the heating on, the
boiler ignites, but not if I only have the HW on.
Blimey, I feel like I'm going round in circles here!
Anyway, thanks again. Guess this is the last thing before getting an
engineer in at great expense.
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