Hot water flowing from vent pipe into loft tank

[Madrab]

@wardr77 , if it's got to the point where the feed/vent is attracting a magnet then it's time to get it cut out and replaced, a cleaner won't be able to break that amount of hardened magnetite down I'm afraid. 5 gets you 10, that if the restriction is cut out and replaced then the pumping over will cease. If not then there's other system issues.

If you are leaving the x400 in the system for a while before that section is replaced then I'd just leave the pump set where it is just now and let the cleaner slowly work it's way around. Any higher speed on the pump and all you'll probably do is increase the amount of pumping over, thereby increasing the amount of dissolved O2 in the system water and all that'll do is promote more corrosion IMO.

 

[DP]

Looks like certain posters do not know why pump over is occurring. They are posting wrong or misleading information perhaps to Look smart. This is not helpful to the person seeking help and direction to resolve the issue
My suggestion to these folk, stop the confusion

 

[wardr77]

That's an interesting idea, though looking at it I would not only need to remove the pump but also the right hand gate valve, I would then have good access to the vent/ feed junction and would be able to dislodge the blockage with a screwdriver and potentially suck it out with vac. Does this seem like a good or very bad idea? Little wary removing gate valve and putting it back on with same olive etc...? Thanks

 

[HERTS P&D]

After the pump is removed, should be able to poke that short section of pipe with a stick of some kind.

Yep, all plumbers carry a stick for cleaning pipework!




Andy

 

[Madrab]

Yup, and once that magnetite is poked loose, any chunks of it that aren't removed then finds its way into the nice new pump or into the 2 port valves or moves to another place and causes another blockage that cant be found. Smashing idea that.

@wardr77 .... It's not a difficult process to drain down to that point and replace the CC feed and vent especially as there is great access, that really is the best place to start IMO

 

[wardr77]

Ok thanks I definitely won't be poking about in there then!! I'll get plumber to cut out and replace section. Thanks

 

[BlueLoo]

Ok thanks I definitely won't be poking about in there then!! I'll get plumber to cut out and replace section. Thanks

Lots of conflicting advise and comments in this thread, though mostly constructive.

If i may suggest though, problems are rarely from just once source, so re read the thread, decide what you think is valid and what you think is not, make a plan and do so from a system perspective, not just an individual point.

That means:

The whole system needs cleaning.
This should include the tanks.

The system needs setting properly,
Pump speeds done correctly and in the correct mode for your system ,(fixed).

ABV needs setting properly.
This can be done once the system is clean and pump is set.

The boiler and rads needs setting properly: Balancing of rads and boiler set correctly (ie for condensing mode if applicable)
Probably have the boiler serviced as well.

Show the plan to your new plumber and listen to his response. You will have learned enough here now to spot if he's a chancer or not.

The above seems a lot, but systems are usually quite tolerant of upset until they are not at which point everything falls apart, not just one thing.
You've already changed the pump and in doing so learned that fixing just one part of a system can be pointless.

All of the above, except the boiler, is easy enough for a DIY project if you are handy enough.

Best of luck.

 

[Exedon]

Ok thanks I definitely won't be poking about in there then!! I'll get plumber to cut out and replace section. Thanks

That's the way to do it!
I would personally discuss with your plumber turning system into sealed.Very few boilers are not compatible cost while drained down should be minimal.
You then get rid of tank open vent and any further pumping over
and will help stop further corrosion.

 

[Madrab]

Looks like certain posters do not know why pump over is occurring. They are posting wrong or misleading information perhaps to Look smart. This is not helpful to the person seeking help and direction to resolve the issue
My suggestion to these folk, stop the confusion

Couldn't agree more @DP

Again @wardr77 ... as always I leave the OP to make their own decisions as to the best way to proceed

 

[Nige F]

As for blocked vent/feed area - I had this in my bungalow some 4 years ago - cut out and replaced - now, recently I changed the Smiths 3 way valve for an S plan . Found the old valve clogged and so far at least a meter of 22 pipe reduced to c.15 mm There may be more to find as I'm replacing a rad soon. It worked probably because there's only 4 rads and a towel rail and c.15mm pipe coped.

 

[BlueLoo]

As for blocked vent/feed area - I had this in my bungalow some 4 years ago - cut out and replaced - now, recently I changed the Smiths 3 way valve for an S plan . Found the old valve clogged and so far at least a meter of 22 pipe reduced to c.15 mm There may be more to find as I'm replacing a rad soon. It worked probably because there's only 4 rads and a towel rail and c.15mm pipe coped.

I'm quite happy that my house is plumbed with compression fittings and PEX piping for the most part.
Easy to strip and clean up any of the copper bits and plastic piping doesn't seem to grab onto the crud at all.

 

[fixitflav]

I haven’t read all the posts on this, but a few comments

the vent pipe is more than 300mm above loft tank.

I thought the recommended figure was 450mm minimum. That’s what my boiler manual says.

I wouldn’t pipe the open vent like that, with the outlet to the vent across the top of a tee. That will exacerbate the pump-over tendency, because it’s easier for the flow to go straight up than turn through 90°. You might be OK, but better IMO to take the vent from a horizontal run.

The cold feed should preferably have a U-bend and come into the bottom of the pipe run. This is to avoid convection warming the water in the F/E tank, which encourages algae growth.

To get pump-over, there must be restriction due to blockage in the pipe between the open vent and cold feed. Problem worse at high flow – high pump setting and low headloss when HW and CH both calling. Restriction anywhere else would reduce the flow and thus reduce the tendency to pump over.

 

[DP]

To get pump-over, there must be restriction due to blockage in the pipe between the open vent and cold feed.

a fact that eludes a few posters here

 

[BlueLoo]

a fact that eludes a few posters here

You comment on this was that it was simply a blockage after the pump.
Which is of no help at all really.

It was only when the OP explained his layout properly that i figured the feed and vent was closed coupled and posted the FAQ pic.

If it was that obvious to you in the first place you should have said so.

The idea of the forum is to help people, not pander to ones ego.

 

[fixitflav]

Or do I need to get the feed / vent junction cut out and replaced with new, theres definitely some magnetic attraction there.

Yes, I think you do