Feeder and Expansion - Vent Pipe

[canonuk]

Hello,

Would someone be able to look at the arrangement of pipes going into and out of the feeder/expansion cistern in my loft.

There are a couple of issues. First, is it ok for the water-out to be attached to the vent?

Secondly, the end of the vent inside the cistern sits below the water level. Is this ok?

Thanks for any ideas/comments

Joe

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[Dan Robinson]

Looks a bodge. Whether it is OK or not depends on the make and model of boiler you have.

The vent pipe shouldn't be in the water though.

 

[stem]

First, is it ok for the water-out to be attached to the vent?

Yes, they should be connected together, however it's not usually done at that location. In the diagram below the two pipes from the left tank are connected into the same pipe just before the pump.

Untitled

• stem
• 14 Jan 2013
• 2

It looks as if the pipe has been moved and was previously connected to the blanked off pipe below. This combined with the rather high 'loop' in the vent pipe suggests to me that this is someone's attempt to fix 'pumping over'. This is where water is pumped through the F&E tank, in via the ventpipe, and out by the outlet. The fact that the end of the vent is below the water line maybe an attempt to prevent air getting into the system. It's not a proper fix but just tackles the symptoms rather than effecting a cure.

 

[onecog]

And the gate valve is a BIG NO NO so get rid quick.

 

[stem]

And the gate valve is a BIG NO NO so get rid quick.

Can you explain why please? It's not in the vent pipe, it's in the cold feed pipe. OK it's not really necessary, but I don't see that the principle is any different to the gate valve installed between every hot water cylinder an its feed tank. Am I missing something?

 

[neiltheplumber]

As Stem says, gate valve not an issue as this is not on the vent. If the valve was turned off then the it would not stop it venting. The main problem looks like feed from the tank to the hot water cylinder has been capped and the feed now goes down to cylinder via the vent pipe which would also be the hot supply from the cylinder. As we can't see the way your hot water cylinder is piped up we may be missing something!

 

[gaswizzard]

Tis a feed and expansion cistern for the CH system and nothing to with the cold water storage cisten , isso valve should not be fitted the cold feed/expansion cistern to boiler end off (british standard code of practice for domestic installations)

 

[onecog]

Am I missing something?

Seems like you are

 

[stem]

Am I missing something?

Seems like you are

Sorry onecog, I wasn't critising your post. As a teenager 30 years ago, I worked a bit with my father who was a registered plumber and I know he never fitted one, I'm just curious that's all and would like someone to explain the technical reason reason why a valve can't be fitted to a F&E feeding a boiler, but is OK on one feeding a hot water cylinder.

Interestingly a quick Google has revealed several schematic flow diagrams, whilst most don't show any isolation valves for clarity I assume, however quite a few do show isolation valves on the F&E for the boiler. For an example see here I can only assume from that, that others are unsure too.

 

[Armo74]

There should be no valves fitted to the open vent pipe or the cold feed on a feed and "expansion" tank, if a valve is fitted and becomes blocked or is accidently closed the water can not expand back into the tank as that is what it is there for. Being as the volume of water in the system will expand by 4%.

As for the cold feed on the hot water cylinder the gate valve is there to isolate the hot water supply to the hot taps.

 

[stem]

OK it could always expand up the vent, but the water in a hot water cylinder will expand when heated too, but it's OK to fit a valve to that.

That's my question why is it ok for one but not the other.

 

[gaswizzard]

OK it could always expand up the vent, but the water in a hot water cylinder will expand when heated too, but it's OK to fit a valve to that.

That's my question why is it ok for one but not the other.

If you are able to give advice on the topic then surely you should know the answer , it ain't rocket science.

 

[onecog]

I'm gonna tell you so as in future you might be able to help someone else

It's so you have a supply of cold water in case of overheating and prevents boiling .this could not happen if acidently left closed or becomes blocked.
You would not want a system running dry would you ?

 

[canonuk]

Thanks for all your comments so far.

Was glad to read that this 'fix' made sense for pumping over, as this is what an engineer told us was happening. In November we had a power flush and at 7pm at the end of a long day with various minor problems arising, the engineer said he had spotted the F&E was full of boiling water and that he couldn't leave it like that. After about another hour he had made these changes to stop the problem and went home. We were just grateful as had heard about what can happen with boiling water in the tank.

Have recently been wondering if this fix was alright. We found last week that the pump was set to 3 and wonder if that had caused the original pumping over - an different engineer had been out a week before the power flush as the boiler broke down and he may have turned pump speed up when trying to determine problem. Our system definitely doesn't need to be on 3.

So, is this current set up (of the vent entering the water, and the cold-feed plumbed into the vent) ok, or is it going to cause problems later on? And could a high pump speed been responsible for a hot F/E tank?

Thanks

 

[HERTS P&D]

In a word......Yes.

normally the pump is on setting 2.

Andy