Mapping my system

[olbasoil]

I am trying to understand and document my system. I have about 15 radiators in 2 zones. The house and extension was built in 1980. There is a single height extension, and the pump and most pipework is in the extension attic, with the boiler immediately below. There are two valves in this attic. There is an cylinder with another valve next to the cylinder, in the airing cupboard (which is at the same level, and about 6 foot away from the last visible exit point in the extension attic). The main attic has the f&e tank.

The trouble is that there is a lot of branchwork, and I suspect it has had some alterations and additions. Within the attic, the pipes are running under insulation, and every so often one disappears through the wall (which is beneath the first floor floorboards in the main house).
All radiators have 15mm pipe coming up from the floor, but I don't want to take up carpet to reveal the pipe runs.

1) Is there a technique for determining what is connected to what when you can't see it? I have tried running the heating and trying to follow the heat, but it is hard to decide.
2) Are wall stud detector machines any good for pipes? I imagine they run a few inches below the floor.

 

[Riley]

May i ask why you're wanting to map it?? Is there a problem??

 

[olbasoil]

I am replacing the pump, and in draining down have noticed that the only draincock leaves all the downstairs radiators filled. (It is behind the boiler, which sends flow and return pipes immediately up to first floor. There is no drainage for the other rads on the ground floor). I'm starting to think that the whole system is poorly designed (or more likely evolved) and would like to understand it better myself, and to share a drawing for other questions. But my current drawing is full of disconnected parts - it might as well say 'here be dragons'!
So any tips for tracing pipes would be much appreciated.

 

[Riley]

Unless you're going to pay for expensive cameras down under floors upstairs the only way to be 100% sure is to have floorboards up. From a time perspective you might be better off just draining the downstairs rads by turning off the valves on one, and removing the rad by draining it into drip trays then attach a hose directly to the radiator valve and draining that way. Once drained, add drain off cocks to suitable points.

 

[doitmyself]

I ... have noticed that the only draincock leaves all the downstairs radiators filled. (It is behind the boiler, which sends flow and return pipes immediately up to first floor. There is no drainage for the other rads on the ground floor.)

It sounds as if the downstairs rads are fed by pipes dropping down from the first floor. The only way to drain them is as Riley suggested. When you do, replace each lockshield valve with one which incorporates a drain off.