New feed & expansion vent

[Careful_Bodger]

It has been suggested that I replace my current close-coupled but individual feed & vent connections (just before the 'pump') with a single pipe, what are the pros and cons?

How long/short should the tail be before the new feed/vent splits into its respective functions? Must the stems of the T section be common with an assymetric reducing T? Is there perhaps an on-line guide?

Is this a recommended approach or should I replace like with like?

I should point out that I am considering replacement since the current arrangement looked a bit gunged up during a recent inspection, and I get water ****ing into the header tank via the vent when the pump (a Grundfos 15/50 about 4 feet below the tank) is set to anything other than its lowest setting - but at least the rads now get nice and toasty. Things bode well for the winter!!

 

[oilman]

I would just replace the bit of the feed pipe that's blocked if I couldn't clear the blockage.

 

[DP]

A vent with feed pipe within 150mm setup before the pump will be at negative pressure at both feed and vent openinings. Blocked feed pipe will result in water dripping from the vent outlet (due to expansion). I would clear/ replace the vent pipe.

If pump over is taking place, then it is a plumbing misfit.

I would seek advice from the makers before embarking on single pipe feed and vent.

 

[PEDANTICVINDICTIVEMAN]

I would fit a Myson Airjec system arranger, this will sort out any pumping over ands sucking down and help to keep things from blocking up in the future, dont forget to treat system with inhibitor on finishing.

 

[oilman]

Blocked feed pipe will result in water dripping from the vent outlet (due to expansion). I would clear/ replace the vent pipe.

I hope you mean to clear/replace the FEED pipe.

I would fit a Myson Airjec system arranger.

I would fix the problem. These systems work fine when they are clean and adding gadgets is not the cure.

I would seek advice from the makers before embarking on single pipe feed and vent.

I agree.

 

[Careful_Bodger]

Thanks for this - but I'm afraid you might have to talk me through this gently

A vent with feed pipe within 150mm setup before the pump will be at negative pressure at both feed and vent openinings.

This may be true but if 'negative pressure', why is there pump over? Why does it only occur on HW & not CH for mid setting & both for high setting?

If pump over is taking place, then it is a plumbing misfit.

I have replaced a clogged Myson Unit 3 with a new Grundfos 15/50 at the same location. I havent yet changed anything else. What & where is the misfit? Presumably me - before anyone else gets in with that one!

Cheers!

 

[oilman]

You probably have a blocked feed pipe just before it connects to the close coupled bit, and within about a foot of it. You will need to get somethjing like a spring to poke up it, or cut the pipe and get to it that way.

The close coupling is so the feed and the vent pipes are at the same pressure so the water doesn't get pushed up the vent pipe.