I have just had my boiler replaced after 22 years of having a gravity fed
C/H system I now have one that is mains pressure (filling loop / gauge). I
have 2 radiators that have been sluggish and hoped that the higher pressure
could improve the situation. It hasn't.
Today I tried:
1. Close both radiator valves and open the drain cock in the valve to
release residual pressure in the radiator.
2. Open lockshield on one end - got a full gush out of the drain cock.
Closed it
3. Open TRV at other end - only get a trickle. Turned it on and off a few
times - got some black particles out. Minor improvement maybe.


Any suggestions? Should I persevere weekly in the hope that if it is due to
crud in the pipe it may eventually soften and get flushed out? Access the
manifold and give the pipes a bit of a rattling about in the hope of
loosening something?

The system did have a X800 cleaner in for about a week before the boiler was
changed. It now has X100 in. Not sure when the problem started - it was
certainly some years ago when I noticed it. I suppose it could even be a
bruised pipes from the original build. The pipes are under chipboard floors
so I can't easily change it.

Any tips or tricks?

"John" wrote in message
news:tGP9o.32819$Nn4.6058@hurricane...
I have just had my boiler replaced after 22 years of having a gravity fed
C/H system I now have one that is mains pressure (filling loop / gauge). I
have 2 radiators that have been sluggish and hoped that the higher pressure
could improve the situation. It hasn't.
Today I tried:
1. Close both radiator valves and open the drain cock in the valve to
release residual pressure in the radiator.
2. Open lockshield on one end - got a full gush out of the drain cock.
Closed it
3. Open TRV at other end - only get a trickle. Turned it on and off a few
times - got some black particles out. Minor improvement maybe.


Any suggestions? Should I persevere weekly in the hope that if it is due
to crud in the pipe it may eventually soften and get flushed out? Access
the manifold and give the pipes a bit of a rattling about in the hope of
loosening something?

The system did have a X800 cleaner in for about a week before the boiler
was changed. It now has X100 in. Not sure when the problem started - it
was certainly some years ago when I noticed it. I suppose it could even be
a bruised pipes from the original build. The pipes are under chipboard
floors so I can't easily change it.

Any tips or tricks?

If the TRV is like ours were, it will have a small steel pin in the middle
that gets stuck down in the off position. You have to take the plastic
shroud off the top and tap the pin to release it and open the valve. In my
opinion this makes TRVs more trouble than they are worth and it is better to
have an ordinary valve and turn it up and down manually if your room
thermostat isn't good enough for you.

Another source of what seems to be 'sluggish' radiators is a three port mid
position valve, that comes up in these columns time and again. These valves
are designed to give the full power of the pump either to the hot water or
to the CH, but they often get stuck in the mid position, where the supply to
the radiators is not so effective. If your radiators were balanced with the
valve fully in the CH only position, they may well not balance with the
valve in the mid position, and you will experience this as some rads seeming
sluggish in warming up. The valves are usually controlled by an actuator of
a clever but failure prone combination of motor and microswitches. These
actuators often fail and get stuck in the mid position, but can be replaced
without having to change the valve itself, so you don't have to drain the
system if you find it has stuck. You can tell if it is stuck by selecting
CH only and then feeling the pipes that come out of the valve: if all three
are hot, it's stuck. Occasionally the valve itself may get stuck, but
usually it is the actuator.

S

"Spamlet" wrote in message
...

"John" wrote in message
news:tGP9o.32819$Nn4.6058@hurricane...
I have just had my boiler replaced after 22 years of having a gravity fed
C/H system I now have one that is mains pressure (filling loop / gauge). I
have 2 radiators that have been sluggish and hoped that the higher
pressure could improve the situation. It hasn't.
Today I tried:
1. Close both radiator valves and open the drain cock in the valve to
release residual pressure in the radiator.
2. Open lockshield on one end - got a full gush out of the drain cock.
Closed it
3. Open TRV at other end - only get a trickle. Turned it on and off a few
times - got some black particles out. Minor improvement maybe.


Any suggestions? Should I persevere weekly in the hope that if it is due
to crud in the pipe it may eventually soften and get flushed out? Access
the manifold and give the pipes a bit of a rattling about in the hope of
loosening something?

The system did have a X800 cleaner in for about a week before the boiler
was changed. It now has X100 in. Not sure when the problem started - it
was certainly some years ago when I noticed it. I suppose it could even
be a bruised pipes from the original build. The pipes are under chipboard
floors so I can't easily change it.

Any tips or tricks?

If the TRV is like ours were, it will have a small steel pin in the middle
that gets stuck down in the off position. You have to take the plastic
shroud off the top and tap the pin to release it and open the valve. In
my opinion this makes TRVs more trouble than they are worth and it is
better to have an ordinary valve and turn it up and down manually if your
room thermostat isn't good enough for you.

Another source of what seems to be 'sluggish' radiators is a three port
mid position valve, that comes up in these columns time and again. These
valves are designed to give the full power of the pump either to the hot
water or to the CH, but they often get stuck in the mid position, where
the supply to the radiators is not so effective. If your radiators were
balanced with the valve fully in the CH only position, they may well not
balance with the valve in the mid position, and you will experience this
as some rads seeming sluggish in warming up. The valves are usually
controlled by an actuator of a clever but failure prone combination of
motor and microswitches. These actuators often fail and get stuck in the
mid position, but can be replaced without having to change the valve
itself, so you don't have to drain the system if you find it has stuck.
You can tell if it is stuck by selecting CH only and then feeling the
pipes that come out of the valve: if all three are hot, it's stuck.
Occasionally the valve itself may get stuck, but usually it is the
actuator.

S



It was sluggish with the old boiler and before I had TRVs. It is definitely
the pipe. The flow from the pipe is poor (observed by opening the integral
drain valve with one valve opened the other closed. Vice-versa and it gushes
out.

"John" wrote in message
news:93W9o.49582$9R.24998@hurricane...
"Spamlet" wrote in message
...

"John" wrote in message
news:tGP9o.32819$Nn4.6058@hurricane...
I have just had my boiler replaced after 22 years of having a gravity fed
C/H system I now have one that is mains pressure (filling loop / gauge).
I have 2 radiators that have been sluggish and hoped that the higher
pressure could improve the situation. It hasn't.
Today I tried:
1. Close both radiator valves and open the drain cock in the valve to
release residual pressure in the radiator.
2. Open lockshield on one end - got a full gush out of the drain cock.
Closed it
3. Open TRV at other end - only get a trickle. Turned it on and off a
few times - got some black particles out. Minor improvement maybe.


Any suggestions? Should I persevere weekly in the hope that if it is due
to crud in the pipe it may eventually soften and get flushed out? Access
the manifold and give the pipes a bit of a rattling about in the hope of
loosening something?

The system did have a X800 cleaner in for about a week before the boiler
was changed. It now has X100 in. Not sure when the problem started - it
was certainly some years ago when I noticed it. I suppose it could even
be a bruised pipes from the original build. The pipes are under
chipboard floors so I can't easily change it.

Any tips or tricks?

If the TRV is like ours were, it will have a small steel pin in the
middle that gets stuck down in the off position. You have to take the
plastic shroud off the top and tap the pin to release it and open the
valve. In my opinion this makes TRVs more trouble than they are worth
and it is better to have an ordinary valve and turn it up and down
manually if your room thermostat isn't good enough for you.

Another source of what seems to be 'sluggish' radiators is a three port
mid position valve, that comes up in these columns time and again. These
valves are designed to give the full power of the pump either to the hot
water or to the CH, but they often get stuck in the mid position, where
the supply to the radiators is not so effective. If your radiators were
balanced with the valve fully in the CH only position, they may well not
balance with the valve in the mid position, and you will experience this
as some rads seeming sluggish in warming up. The valves are usually
controlled by an actuator of a clever but failure prone combination of
motor and microswitches. These actuators often fail and get stuck in the
mid position, but can be replaced without having to change the valve
itself, so you don't have to drain the system if you find it has stuck.
You can tell if it is stuck by selecting CH only and then feeling the
pipes that come out of the valve: if all three are hot, it's stuck.
Occasionally the valve itself may get stuck, but usually it is the
actuator.

S



It was sluggish with the old boiler and before I had TRVs. It is
definitely the pipe. The flow from the pipe is poor (observed by opening
the integral drain valve with one valve opened the other closed.
Vice-versa and it gushes out.

Is this with the pump on or off?
If it is not on then water may not be able to flow out of that section of
pipe, especially if it is on a spur.

You should not be saying "it is definitely the pipe" but "why is water not
coming from this particular pipe", and that depends on a number of other
things:

If the TRV is on the input end of the rad and especially if this is a low
point on the system, then that is where you would expect the sludge to
collect in the pipe, but it rather depends on what is on the other end or
the pipe; how much is horizontal and how much vertical, and, as I said,
whether it is getting the full flow from the pump. If for example the pipe
is 'T' d off another pipe, water will prefer to go straight across rather
than round the corner, and the rads have to be balanced to offset this
tendency, but even if they are balanced and your rad is often off or on a
low flow, then that is where the crud will settle out. You may be able to
blast it through by closing all the other rads, opening the sluggish one
full on both sides, selecting CH only, and putting the pump on full speed.
Repeat with all the other rads in turn, and this should at least
redistribute any sludge. You then have to rebalance to get all the rads to
the same temp via the lock shields, before putting the TRVs back to your
preferred setting. (This can take some time and fiddling. Esp if your
3port valve or pump are not at their best.)

Seriously though: Did you check if you have a three port valve? because if
you do and it is 22years old there is a good chance that is has not been
working properly for a long time. You may also find that bleeding the pump
helps.

If none of this helps, then you are looking at replacing that length of
pipe, unless you can find some way of pulling a 'test-tube brush' through
it. But as you say you have 2 sluggish radiators, I'd definitely look to
your balancing and your valve before doing anything drastic.

S

"Spamlet" wrote in message
...

"John" wrote in message
news:93W9o.49582$9R.24998@hurricane...
"Spamlet" wrote in message
...

"John" wrote in message
news:tGP9o.32819$Nn4.6058@hurricane...
I have just had my boiler replaced after 22 years of having a gravity
fed C/H system I now have one that is mains pressure (filling loop /
gauge). I have 2 radiators that have been sluggish and hoped that the
higher pressure could improve the situation. It hasn't.
Today I tried:
1. Close both radiator valves and open the drain cock in the valve to
release residual pressure in the radiator.
2. Open lockshield on one end - got a full gush out of the drain cock.
Closed it
3. Open TRV at other end - only get a trickle. Turned it on and off a
few times - got some black particles out. Minor improvement maybe.


Any suggestions? Should I persevere weekly in the hope that if it is
due to crud in the pipe it may eventually soften and get flushed out?
Access the manifold and give the pipes a bit of a rattling about in the
hope of loosening something?

The system did have a X800 cleaner in for about a week before the
boiler was changed. It now has X100 in. Not sure when the problem
started - it was certainly some years ago when I noticed it. I suppose
it could even be a bruised pipes from the original build. The pipes are
under chipboard floors so I can't easily change it.

Any tips or tricks?

If the TRV is like ours were, it will have a small steel pin in the
middle that gets stuck down in the off position. You have to take the
plastic shroud off the top and tap the pin to release it and open the
valve. In my opinion this makes TRVs more trouble than they are worth
and it is better to have an ordinary valve and turn it up and down
manually if your room thermostat isn't good enough for you.

Another source of what seems to be 'sluggish' radiators is a three port
mid position valve, that comes up in these columns time and again.
These valves are designed to give the full power of the pump either to
the hot water or to the CH, but they often get stuck in the mid
position, where the supply to the radiators is not so effective. If
your radiators were balanced with the valve fully in the CH only
position, they may well not balance with the valve in the mid position,
and you will experience this as some rads seeming sluggish in warming
up. The valves are usually controlled by an actuator of a clever but
failure prone combination of motor and microswitches. These actuators
often fail and get stuck in the mid position, but can be replaced
without having to change the valve itself, so you don't have to drain
the system if you find it has stuck. You can tell if it is stuck by
selecting CH only and then feeling the pipes that come out of the valve:
if all three are hot, it's stuck. Occasionally the valve itself may get
stuck, but usually it is the actuator.

S



It was sluggish with the old boiler and before I had TRVs. It is
definitely the pipe. The flow from the pipe is poor (observed by opening
the integral drain valve with one valve opened the other closed.
Vice-versa and it gushes out.

Is this with the pump on or off?
If it is not on then water may not be able to flow out of that section of
pipe, especially if it is on a spur.

You should not be saying "it is definitely the pipe" but "why is water not
coming from this particular pipe", and that depends on a number of other
things:

If the TRV is on the input end of the rad and especially if this is a low
point on the system, then that is where you would expect the sludge to
collect in the pipe, but it rather depends on what is on the other end or
the pipe; how much is horizontal and how much vertical, and, as I said,
whether it is getting the full flow from the pump. If for example the
pipe is 'T' d off another pipe, water will prefer to go straight across
rather than round the corner, and the rads have to be balanced to offset
this tendency, but even if they are balanced and your rad is often off or
on a low flow, then that is where the crud will settle out. You may be
able to blast it through by closing all the other rads, opening the
sluggish one full on both sides, selecting CH only, and putting the pump
on full speed. Repeat with all the other rads in turn, and this should at
least redistribute any sludge. You then have to rebalance to get all the
rads to the same temp via the lock shields, before putting the TRVs back
to your preferred setting. (This can take some time and fiddling. Esp if
your 3port valve or pump are not at their best.)

Seriously though: Did you check if you have a three port valve? because if
you do and it is 22years old there is a good chance that is has not been
working properly for a long time. You may also find that bleeding the
pump helps.

If none of this helps, then you are looking at replacing that length of
pipe, unless you can find some way of pulling a 'test-tube brush' through
it. But as you say you have 2 sluggish radiators, I'd definitely look to
your balancing and your valve before doing anything drastic.

S


The boiler is new.
It is a pressurised system.
Opening one end and the water gushes out.
Opening the other end and it is a trickle.
It has nothing to do with diverters or balance.
Mains pressure will be more effective when one end is opened than any amount
of circulating with a pump (circulator)
The 8mm pipes are connected to a proper manifold.