Expansion vessel failure

Brosgiz

Hi
I'm new to this but I'm hopeful someone could Give me answers!
My knowledge of plumbing is not the greatest but my heating system consists of a stove with a back boiler and an oil boiler in the garage. Along with a pressurised system.
The expansion vessel is located above the dhw cylinder and I have this replaced 6 times over the last 5 years.
Can anyone share a bit of light on why this is the case?
Thanks in advance..

Outkast_IRE

Are you saying your cold water and hot water system is pressurised or your central heating system is pressurised or both ?
Does the expansion vessel belong to the heating system or the domestic water system ?

Brosgiz

Outkast_IRE wrote: »

Are you saying your cold water and hot water system is pressurised or your central heating system is pressurised or both ?
Does the expansion vessel belong to the heating system or the domestic water system ?

As far as I'm aware it's just the cold and hot water that is pressurised.. how do I go about finding out if the heating is pressurised??
The expansion vessel belongs to domestic water system...

Outkast_IRE

Brosgiz wrote: »

As far as I'm aware it's just the cold and hot water that is pressurised.. how do I go about finding out if the heating is pressurised??
The expansion vessel belongs to domestic water system...

I thought connecting a stove to an unvented water system was a big no no. The fact that you have went through so many vessels would have me worried that the pressure in the system is building quite high when the stove is going and causing failure, a potentially catasrophic situation if this is actually whats happening.

Brosgiz

Outkast_IRE wrote: »

I thought connecting a stove to an unvented water system was a big no no. The fact that you have went through so many vessels would have me worried that the pressure in the system is building quite high when the stove is going and causing failure, a potentially catasrophic situation if this is actually whats happening.

And the solution is?😕

As above you cannot have a uncontrollably heat source feeding a unvented cylinder for safety reasons.

If your having issues with your domestic hot water expansion vessel it maybe excessive pressure related or something silly like the vessel is fitted on the hot water cylinder outlet pipework.

If it's your heating expansion vessel it then tends to be heating water contamination that attacks the innards of the expansion vessel.

When it's due have your boiler serviced by a person who understands plumbing and ask for them to check your installation (this would be made much easier if you have your unvented cylinders manufacturers instructions)

Brosgiz

My heating system consists of an expansion tank and a water tank in the loft. So would I be correct in saying it is a vented system?
U say it's silly to have vessel on hot water outlet pipework. Yip you guessed it, that is exactly where it is located, and I'm petrified that I will have a big bang some night.
I wouldn't mind but I have had 3 different plumbers in to look at it and any of them never said this was incorrect! A neighbour who is a handy man once suggested removing the vessel and fitting it on the cold inlet pipe work. Do this make sense??

Brosgiz

Brosgiz wrote: »

My heating system consists of an expansion tank and a water tank in the loft. So would I be correct in saying it is a vented system?
U say it's silly to have vessel on hot water outlet pipework. Yip you guessed it, that is exactly where it is located, and I'm petrified that I will have a big bang some night.
I wouldn't mind but I have had 3 different plumbers in to look at it and any of them never said this was incorrect! A neighbour who is a handy man once suggested removing the vessel and fitting it on the cold inlet pipe work. Do this make sense??

I would suggest starting at the beginning which would be getting a tame plumber in and asking him to read the fitting instructions for your unvented cylinder(assuming that's what you have:) )

What the manufacturers instructions will most likely require is for the expansion vessel to be fitted on the cold inlet supply pipe as close as is practical to the cylinder, you cannot fit the expansion vessel on the hot water outlet pipework as the heat has a negative impact on the vessels innards.

Also you cannot fit a stove directly to a unvented cylinder (assuming again:) ) if you do have a stove feeding a unvented cylinder directly then you are reliant on the correct installation of the cylinders safety devices and pipework to protect you from ant negative outcome.

Brosgiz

Brosgiz wrote: »

My heating system consists of an expansion tank and a water tank in the loft. So would I be correct in saying it is a vented system?

Most likely, but I'd still have it confirmed by a local tame plumber.

RJF

What is a "tame" plumber???
Are they an endangered species???

RJF

RJF wrote: »

What is a "tame" plumber???
Are they an endangered species???

Iv had some of them try and bite me:eek:

The domestic plumbing industry is brutal as there is no restriction or policing on who carries out plumbing work but there are lots and lots of good plumbers out there and none of them have tried to bite me hence the tame ting:)

Brosgiz

gary71 wrote: »

What the manufacturers instructions will most likely require is for the expansion vessel to be fitted on the cold inlet supply pipe as close as is practical to the cylinder, you cannot fit the expansion vessel on the hot water outlet pipework as the heat has a negative impact on the vessels innards.

So pretty much my 3 qualified plumbers haven't a clue what they are at at my diy handy man has more knowledge of their profession!
Thanks for that Gary, so change my vessel to the cold inlet seems to be the soloution (hopefully). I have another plumber in mind I might contact him and see is he tame

hatchman

Quick question related to the expansion vessel what should the pressure be set at ? I have a pressure pump and a pressure vessel too. The pump cuts out at about 3.5 bar so I thought the expansion vessel should be set just above 3.5 bar but when I replaced vessel at this pressure after water was heated there is a lot noise once shower or tap is turned on. The noise stops after the water runs a bit. So I am thinking pressure should be lower so I let some off and it seems to have got worse ! Any ideas as it worked before without and banging noise

hatchman

hatchman wrote: »

Quick question related to the expansion vessel what should the pressure be set at ? I have a pressure pump and a pressure vessel too. The pump cuts out at about 3.5 bar so I thought the expansion vessel should be set just above 3.5 bar but when I replaced vessel at this pressure after water was heated there is a lot noise once shower or tap is turned on. The noise stops after the water runs a bit. So I am thinking pressure should be lower so I let some off and it seems to have got worse ! Any ideas as it worked before without and banging noise

The pressure of a vessel is usually set to match the incoming water pressure.

hatchman

gary71 wrote:

The pressure of a vessel is usually set to match the incoming water pressure.

Thanks Gary I have a pressure pump for the whole house which is fed from a tank in attic so it varies i think from around 1 bar when pump turns on to 3.5 when pump turns off. This pump is before the hot water cylinder which is tee'd to cylinder and to cold water feeds. I was thinking I should set it about 3.5 bar in this set up ?

hatchman

hatchman wrote: »

Thanks Gary I have a pressure pump for the whole house which is fed from a tank in attic so it varies i think from around 1 bar when pump turns on to 3.5 when pump turns off. This pump is before the hot water cylinder which is tee'd to cylinder and to cold water feeds. I was thinking I should set it about 3.5 bar in this set up ?

Yea, I'd set it to the maximum incoming pressure.

hatchman

gary71 wrote:

Yea, I'd set it to the maximum incoming pressure.

Thanks Gary I'm going to take out the expansion vessel tomorrow check pressure and I think I'll do the same with pressure vessel. Have a new vessel which I will fit hope it solves issue.

Dtp1979

hatchman wrote: »

Thanks Gary I'm going to take out the expansion vessel tomorrow check pressure and I think I'll do the same with pressure vessel. Have a new vessel which I will fit hope it solves issue.

Did it work after?

hatchman

Yes perfect so far ! Set it around 50 psi and and no issue since. I have pressure gauge fitted on pipe work before expansion vessel and also have guage at the pressure vessel so I can see real time what is the pressure is both sides of the hot water cylinder