Vent pipe spurting every 5 mins when heating and hw on

[jamescarter1000]

I have a weird problem that started about 2 months ago.

AFter my boiler is on for hw or htg (but for hw mainly it seems worse) after about 1/2 hour water starts to shoot out of the vent pipe (for about 5 seconds at a time) and then more water back down the cold feed pipe. This happens every 5-10 minutes and is very loud and annoying. Why is this happening and is there anything I can do to cure it?

 

[namsag]

Your boiler thermostat has gone and needs replacing

 

[granty1]

also check pump, gud way of doing this, take silver cap of pump head and insert a screw driver into it if your able to stop it then it could be pump,

 

[jamescarter1000]

can't be pump, 2 new pumps have been added in past 10 years.

if it was boiler stat wouldnt the discharge be intermittent and just a dribble?

 

[seco services]

sounds like a sludged system if its had two pumps.

 

[jamescarter1000]

well i have been reading posts on here on the FAQs and my cold feed isnt blocked as i drained the system and the header tank emptied to the outlet level. the water shoots out every 5-10 mins, like opening a tap kind of amount/force. why would this being down to sludge? what can i do to cure it please?!


also i turned the boiler stat to 0 and back up again (max setting is 6) and the boiler stopped firing and started again - so the boiler stat could be OK?

 

[seco services]

if you have a air seperator joining the cold feed and vent they can block.

why have you had two pumps in that short time ?
whats the condition of the water when you drained it ?
what is the boiler stat set to ?

 

[jamescarter1000]

i understand the cold feed and vent pipe join can become sludged/blocked. but mine seems to be under the floor, the pipes then go up to the f & e (ontop of shelf in cupboard in bedroom) and the pipe to the pump comes up from the floor near it (only about 6 inches before it enters the pump).

I drained the system not all, but for about 10-15 mins and it was clear water; the draining stopped for 2 mins, etc, well it slowed down to be precise, then started at normal rate again. but if it is sludged, why is the water clear?? maybe it is dirty but i only drained the lower part perhaps??

 

[seco services]

not saying its 100% down to sludge as i don't know your system.

sludge can go hard over time and restrict pipes.
as for draining a rad the sludge don't always come out till you remove rad and tip it up.
many blockages near vents etc need to be cut out as chemicals won't shift them.

 

[jamescarter1000]

oh great! i cant see any way to get floors up without moving the cylinder and all pipes, including pump and 3 port valve!

i drained it though, so does this mean the blockage was NOT that bad-as water did come out of the drainng valve?

is a cleaner in the header tank a good idea? will it damage anything?

 

[seco services]

worth trying a cleaner won't damage anything, thats what their for.
try sentinel x 400 or x800

 

[jamescarter1000]

ok will trey a cleaner. reading a post on here earlier, someone said that cleaner caused their boiler light to go out and not come on again? can this be true due to the sludge, etc removed from the cleaner? i just want to be sure before i try it!

also can i rule out the boiler stat not working properley?

 

[sooey]

Your boiler thermostat has gone and needs replacing

If namsag says that, you might do well to listen to him. He seems to know what he's on about

 

[jamescarter1000]

but how do i know for sure it has gone? it seems to turn on and off when i twist it. also the water ejection is more than a dribble and is like a pour which last for 5-10 seconds a time

 

[seco services]

not seen the post but cleaner won't cause any problems with a boiler going out sounds like another issue with the system.

sludge will cause more problems than anything as the system can overheat due to circulation problems.

i've never had a boiler fail due to using a cleaner any way.

why have you had two pumps fitted in 10 yrs ?