Boiler starts up when cold water tap turned off

[malk]

Hi all,

I've got a Vaillant turbomax boiler, and when i turn the cold tap off, the boiler starts its ignition sequence as for hot water demand. The only way i can avoid this is to turn the cold water off *very* slowly.

I've also noticed the igition sequence starting when my next door neighbours draw water!!

Any ideas what's going on? Is there something i can try adjusting myself? (i can't afford to get an engineer to look at it)

Thanks in advance

 

[gas4you]

Sounds possibly like a 'dead leg' in your pipe work somewhere.

 

[Polly1]

I had this problem. It was because turning off the cold tap increased pressure in the cold supply which tricks the boiler into thinking a hot tap has turned on.

The solution is cheap and easy, fitting a non-return valve to the cold pipe feeding the boiler will stop it for less than a tenner.

What this does is keeps the water supply pressure to the boiler constant when the cold taps are turned on.

 

[pannierstan]

I had this problem. It was because turning off the cold tap increased pressure in the cold supply which tricks the boiler into thinking a hot tap has turned on.

The solution is cheap and easy, fitting a non-return valve to the cold pipe feeding the boiler will stop it for less than a tenner.

What this does is keeps the water supply pressure to the boiler constant when the cold taps are turned on.

This is a work around and should not have to be done if the pipework both hot and cold is right without any deadlegs as mentioned.
Either find the dead legs or fit an arrestor.

Stan

 

[malk]

thanks everyone

how does one find a dead leg and wouldn't a non-return valve be easier to fit than an arrestor (whatever that may be)

 

[tally100]

Whats a dead leg?

 

[JonB]

Dead Leg.
A redundant pipe capped of.
Not a good idea causes stagnant water.

 

[BoxBasher]

Dead Leg.
A redundant pipe capped of.
BREACH OF WATER REGS causes stagnant water.

corrected free of charge

 

[JonB]

Thanks Box
A moment of senility.
Retired Factory Maintenance Engineer

 

[Agile]

I had this problem. It was because turning off the cold tap increased pressure in the cold supply which tricks the boiler into thinking a hot tap has turned on.

The solution is cheap and easy, fitting a non-return valve to the cold pipe feeding the boiler will stop it for less than a tenner.

What this does is keeps the water supply pressure to the boiler constant when the cold taps are turned on.

Its far better to fit the non return valve AFTER the boiler so any expansion in the boiler can be absorbed in the supply.

If yoyu must fit it before the boiler then you should theoretically fit a shock arrester configured as an expansion vessel on the tap side.

Tony

 

[Aref_Bilal]

thanks everyone

how does one find a dead leg and wouldn't a non-return valve be easier to fit than an arrestor (whatever that may be)

Malk, i had this problem with my Vallaint Turbomax Boiler which started after some plumbing work. However, problem was instantly resolved when the 'Dead Leg' was cut off.

A 'Dead Leg' is a pipe connected to your system that goes nowhere (ie.. to a bath, basin or anywhere else). In my case, the 'Dead Leg' was an extension of the hot water pipe that ran behind the bath and capped off 'Nowhere'. Just an extra pipe containing stagnant water. Your 'Dead Leg' pipe could be somewhere near a recent plumbing work.

When this pipe was cut off, the boiler went back to normal immediately.

Hope this helps you.

 

[Aref_Bilal]

Hi all,

I've got a Vaillant turbomax boiler, and when i turn the cold tap off, the boiler starts its ignition sequence as for hot water demand. The only way i can avoid this is to turn the cold water off *very* slowly.

I've also noticed the igition sequence starting when my next door neighbours draw water!!

Any ideas what's going on? Is there something i can try adjusting myself? (i can't afford to get an engineer to look at it)

Thanks in advance

Malk, i had this problem with my Vallaint Turbomax Boiler which started after some plumbing work. However, problem was instantly resolved when the 'Dead Leg' was cut off.

A 'Dead Leg' is a pipe connected to your system that goes nowhere (ie.. to a bath, basin or anywhere else). In my case, the 'Dead Leg' was an extension of the hot water pipe that ran behind the bath and capped off 'Nowhere'. Just an extra pipe containing stagnant water. Your 'Dead Leg' pipe could be somewhere near a recent plumbing work.

When this pipe was cut off, the boiler went back to normal immediately.

Hope this helps you.

 

[acquiesce1979]

I had the same problem and it is much easier to 'get rid' of the dead leg. In my case has been happening for ages but with a kitchen refurb only became noticable as I now have sick near boiler.

Turns out the pipe is probably above my newly fitted ceiling and under newly laid bathroom floor.

Soloution
Fit a 160ml approx Pressure Vessel (mine is a Altecnic .16ltr Stainless Steel Pressure Vessel) and a non return valve or check valve on the cold main TO THE BOILER sorted.

although costs around £30 for the lot.