CH drain valve won't shut

[phloaw]

Today I drained my CH/HW. This is a standard vented, pumped S plan with two electric valves, and I'm in UK.
I was lucky enough to have a drain valve underneath ground floor, relatively accessible, see pics:

However, upon refilling the system, I found out that that valve will rotate endlessly, and won't guarantee proper isolation: it's stripped.

I was thinking to add an isolating (aka service) valve past the old one, i.e., along the pipe in the bottom part of the images.
Something like this:

Do you think that will work? Or is there a risk that the old valve will leak when the new one is shut? Do you foresee any other possible problem?

Any feedback welcome!

Thanks!

 

[steadyon]

1. If you can, remove the handle from the old valve and rotate the spindle with a spanner / pliers / grips.
2. The type of valve you picture isn't really designed for central heating temperatures, but a good quality one would probably do.

 

[phloaw]

1. If you can, remove the handle from the old valve and rotate the spindle with a spanner / pliers / grips.

It's not visible from the pics, but the old one is in a really unfortunate position: I'd probably need removing more subflooring.
Can I ask why you are suggesting that?

2. The type of valve you picture isn't really designed for central heating temperatures, but a good quality one would probably do.

Mmmm, the manufacturer's specification sheet says:

TECHNICAL DATA
Maximum working pressure16 bar
Maximum working temperature-20ºC to +90ºC

Should I trust that? It's above all to avoid having to find a plumbing supplier open during these times tomorrow

 

[moonlight]

Where does the water drain too? Have you thought about a lever valve instead? a bit more money, but more reliable.

https://www.NoLinkingToThis/p/pegler-ball-valve-red-15mm/21289

 

[phloaw]

Where does the water drain too?

Good question. I cannot see where the drain pipe goes (bottom of second pic). I assume it goes either to waste piping or directly outside. When I drained the system I couldn't see any wet spot either inside or outside

Wrt the valve yes, I know a full bore valve would be better. It's difficult to source things these days, though, and I wanted to finish, so I put what I had. I meant to replace it when I have time but, realistically, I won't keep my own promise
Hope the thing won't leak

 

[Stigster]

If it isn't leaking now, it'll probably be OK. As already mentioned, a good quality lever ball valve would be preferable but if you've already fitted the valve you have and it's not letting by I'd leave it for now unless you are desperate to get back in there and do it!