Hot water flowing from vent pipe into loft tank

[denso13]

No it doesn't

Yes it does, it is a feed and expansion cistern, the cistern takes up water expansion through the feed.

 

[BlueLoo]

With the pump off the water level in the F&E cistern and vent pipe will be same, therefore having the same pressure. It doesn't matter how far apart they are.

Agreed.

It's an important point to know though when the pump is running.

 

[BlueLoo]

FAO: OP.

This is why you listen to all advise and do your own research before embarking on anything

Opinions differ.....

 

[JohnD]

Opinions differ.....

facts don't

 

[Madrab]

Keep the valve open, then it's an open vent system.

Until the customer goes, oooo, what's this for, lets close it ....

OK, had enough now, you really don't know what you are talking about ....

No it doesn't. A vent is for venting, a feed is for feeding. If your feed is venting, I suggest you call a plumber.

Well if I actually needed a plumber, something that I have actually been for more years than I'd like to recall, it certainly wouldn't be you I'd be calling, you're downright dangerous ... and I'm am now going to ignore anything you have to say on this subject as again you really don't know what you are talking about.

@wardr77, unfortunately your post has been somewhat highjacked by erroneous and ill informed advice, as always in an open forum it is up to you what advice you listen to and what advice you don't.

 

[denso13]

No it doesn't.

You are just wrong. The clue is in the name, feed and expansion cistern.

 

[Dereekoo]

Here is a very simplified diagram of a central heating system. If the pump is pumping 10l/s its must also be sucking 10l/s so everything is in equilibrium i.e. in = out, and there is no excess flow to go up the vent pipe. Even if the pump was suddenly able to pump 1000l/s the net flow around the system would be 1000l/s, in equilibrium, and still there would be no excess flow to go up the vent pipe. If a constriction/blockage was put at point A and the flow restricted to 2l/s then net flow around the system would be 2l/s, equilibrium, and still there would be no excess flow to go up the vent pipe. The only time that there would be excess flow to go up the vent pipe is if there was a restriction at point B (say forward flow limited to 1l/s) and to satisfy the pumps suction requirement (say 10l/s) and to maintain equilibrium, flow would need to be sucked down the feed pipe from the header tank (9l/s), and, since only 1l/s can go forward at point B even though 10l/s is being pumped around to it, 9l/s would have to go up the vent pipe into the header tank. Therefore the problem is around point B as flagged up by Madrab earlier and presumably why vent to feed pipe distance is, I believe, limited to 150mm.

 

[denso13]

Excessive expansion (aka venting) goes in EXPANSION pipe (aka vent pipe).

No, it really doesn't. Expansion isn't venting.

Expansion up the feed to the cistern is normal, venting over isn't and suggests something is wrong.

Unless I've misunderstood all throughout my apprenticeship and the last 40 years installing.

 

[wardr77]

Until the customer goes, oooo, what's this for, lets close it ....

OK, had enough now, you really don't know what you are talking about ....


Well if I actually needed a plumber, something that I have actually been for more years than I'd like to recall, it certainly wouldn't be you I'd be calling, you're downright dangerous ... and I'm am now going to ignore anything you have to say on this subject as again you really don't know what you are talking about.

@wardr77, unfortunately your post has been somewhat highjacked by erroneous and ill informed advice, as always in an open forum it is up to you what advice you listen to and what advice you don't.

Appreciate all the advice given, some of the discussion is somewhat over my head. There is definitely magnetic attraction at the vent / feed junction so replacing that section is probably a good place to start ( not by me though!!) I've just been in the loft and emptied the F&e tank and gave it good clean, dont like the idea of all the crud in that tank circulating through new pump while I have the pump over problem. The following pic shows rate of flow from vent pipe on pump setting 1, not massive, but continuous, and water still pretty hot. Thanks again

 

[JohnD]

the easiest and quickest thing you can do is put in a litre of X400

it can be circulating, and possibly removing sediment, while the arguments go on and while you wait for a plumber.

If the water is more than about 4 inches deep (2 inches above the F&E pipe outlet), try to adjust the ball float valve to reduce depth.

Sediment often hardens, especially when it combines with limescale, so the pipe may still need replacing or scraping out.

 

[JohnD]

btw I've decided it is a waste of time engaging with nutjob, who is mistaken.

 

[wardr77]

Ok I can do that, how long can i safely leave the x400 in the system for? Thanks

 

[BlueLoo]

Are you absolutely sure the pump is put in the correct way round?

Flow is from right to left, vent pipe on the far right, feed pipe between it and the pump?

 

[DiyNutJob]

Unless I've misunderstood all throughout my apprenticeship and the last 40 years installing.

I am surprised in 40 years, you have not understood angles and small diameters are bad for flowing.

 

[JohnD]

Ok I can do that, how long can i safely leave the x400 in the system for? Thanks

"Safely" for ever, it does not cause damage. There are other more aggressive cleaners that have to be removed and flushed out within hours. IMO they are not suitable for DIY use.

"Effectively" drain out after 4 weeks, and it will bring suspended and loosened sludge and sediment with it, hence the rinse and drain. After about 4 weeks it starts to loose its cleansing properties and the dirt settles down again. In your case it will not be so bad because a lot of it will get trapped in the filter. most of the cleaning will happen in the first week or so.