What's the purpose of this strange return pipe?

GDB2222

pieroabcd said:

Yes same size.
I don't think that it makes any improvement in practice, but having a uniform system with all valves if the same type and in the same position has its advantages (like if you call a plumber they won't have excuses) and if in the future it comes to sell (not planning at all) at least I won't leave behind the disasters that I found when i bought the house two years ago.
Anyway, no need to drain the system: the valves can be just unscrewed and inverted.

"Anyway, no need to drain the system: the valves can be just unscrewed and inverted."

Now, I'm really, really intrigued. 

bjorn_toby_wilde

GDB2222 said:

pieroabcd said:

Yes same size.
I don't think that it makes any improvement in practice, but having a uniform system with all valves if the same type and in the same position has its advantages (like if you call a plumber they won't have excuses) and if in the future it comes to sell (not planning at all) at least I won't leave behind the disasters that I found when i bought the house two years ago.
Anyway, no need to drain the system: the valves can be just unscrewed and inverted.

"Anyway, no need to drain the system: the valves can be just unscrewed and inverted."

Now, I'm really, really intrigued. 

Post a video?

pieroabcd

Very easy, but no video sorry .
After disconnect the nut connecting the radiator to the valve I used the hexagonal key as a plug, to prevent the water from flowing, then I prepared the replacement with an equivalent piece (I had to because the new Trv has 1/2 inch opening, while the old one was 1/2 inside the radiator and 3/4 outside) with a shred of tissue inside to use as plug. Finally I swapped the old connector with the new one. Some water leaked, but very little.
Some water leaked from the water pipe too, but in the meantime I had already drained some water from another radiator, but definitely not the whole system.

WIAWSNB

pieroabcd said:

Very easy, but no video sorry .
After disconnect the nut connecting the radiator to the valve I used the hexagonal key as a plug, to prevent the water from flowing, then I prepared the replacement with an equivalent piece (I had to because the new Trv has 1/2 inch opening, while the old one was 1/2 inside the radiator and 3/4 outside) with a shred of tissue inside to use as plug. Finally I swapped the old connector with the new one. Some water leaked, but very little.
Some water leaked from the water pipe too, but in the meantime I had already drained some water from another radiator, but definitely not the whole system.

Blimey!

I presume your system is sealed - unvented? 

It can be very surprising how easy it is to swap parts on such systems without a significant loss of water. I changed two 2-port valves on mine after doing a test - ie, releasing one connection to see what happens! Fully depressurise, of course, but then just get all the bits ready to swap, inc a smear of compound if needed. A couple of towels underneath tobesuretobesure. And, if the worst case happens and you cannot complete the task, then the 'flow' is dead easy to stop using a plug as you suggest. 

With sealed systems, air needs to get in to the pipework via the same route as any water escapes. For a rad, just shut off the end not being tackled, and drain down the whole rad if you wish. Then you only have a single point where water can get out, and air get in - worst case there is that you have 'glugs'. But if you place yer thumb or even a piece of tape over it, the flow will stop, since air cannot get in. 

pieroabcd

Yes, it's sealed. Surprising what magic s whiff of air can do!

Jumblebumble

HHarry said:

pieroabcd said:

Ive Just noticed a bolt under the straight part. I imagine that it's the opening valve?

Yes - they usually have a square head.  A word of caution, once opened they don’t always seal very well if the rubber washer has perished or some grit gets stuck in it.

I would add to your excelent advice that my plumber constantly has to replace the washers after bodgers  have over tightened the square head
They dont need much tightening