How common were single pipe CH systems in the 1960's?

I'm trying to determine whether I have a single pipe CH system. Downstairs it's hard to say because everything's burried in screed. The radiators are all bottom-entry and bottom-exit, and have TRV's and seem to function well.

The one rad that's exposed has both pipes plumbed in to the same single 22mm pipe, but there's another 22mm pipe running alongside and I wonder if a previous DIY'er has simply plumbed it in wrong.

I think I need to bite the bullet and pull more carpet and floorboards up, but being tongue and groove floor boards (1960's) it's a messy job. I was wondering single pipe was pretty rare anyway?

Cheers

Gary

Quite common.
If teed into same pipe guess what??
Adjacent pipe could be a continuation of the loop.

Terrywookfit said:

Adjacent pipe could be a continuation of the loop.

Click to expand...

Thanks - having looked at it again I suspect I have two single-pipe loops - one that runs the downstairs rads and one that runs the upstairs ones.

Single pipe systems are popular today in non domestic systems. They work ok in houses even with a modern boiler attached if balanced well