Pipe freezing - Electric or Gas?

[Porker]

I am about to embark on a major kitchen refit which involves pulling up a large tiled floor, moving and renewing pipework to a number of radiators which have had the copper put straight into wet concrete in the late 70's. Having drilled through one of these pipes by accident and having to renew a short section, they are suffering a bit and I want to replace as I'm laying rather expensive tiles over the top. Some of them I am going to run above ground but due to the layout of the house I have no choice but to put some pipes under the floor. As I'm doing this over a few weeks, I don't want to drain down the system and refill every day (I have small children so want to keep some heat on). My question is whether the commercial gas freezing kits are any good. I would prefer an electric unit but these are expensive (even second hand). Due to the timeframe hiring would be expensive so I would rather buy and sell on afterwards.
Any advice on how to protect the pipes would also help. I have been told to put copper in a felt sleeve but have also considered plastic. Any preferences?

 

[Nige F]

I hired an electric one and it was brilliant...Try eBay Various opinions on sleeving, I prefer plastic overflow pipe for 15mm. copper.

 

[Porker]

Thanks for the tips. I had thought of overflow pipe as well but didn't know if this was OK.

 

[chrishutt]

Just drain down once and fit isolating valves to all the sections that you will have to alter. Then you can isolate as and when necessary.

Burried pipes are best in plastic in a duct (next size up of plstic pipe?) since they can be removed and replaced in the event of some dumb cluck drilling through them.

 

[ChrisR]

which have had the copper put straight into wet concrete in the late 70's

Do replace all of it!
Even new electric pipe freezers seem to be quite troublesome, and you can guess where they go once the guarantee's run out. Have had problems with ebay items.
The diy cans are colder than the "pro" ones, which can work out more expensive. Don't try to freeze warm pipes!

 

[Porker]

I shall fit isolating valves and as you state I could do this with only one drain down. probably give that a go. Good point about second hand freezer. Got to think why they are selling it.

BTW the wall thickness on the 15mm copper I replaced was around 1/2 of the new piece, the concrete must have attacked it and probably still is.

I have had a few issues with Ball-o-fix in the past (mainly leaking on the spindle). A lot of the wheel valves in this house are also seized (used some advice to slacken gland nut which freed most up). Was probably going to buy Pegler 1/4 turn valves as I understand they are better quality. Any comments on using these?

 

[chrishutt]

Was probably going to buy Pegler 1/4 turn valves as I understand they are better quality

Good thinking.

 

[brumylad]

make sure you get "full bore" isolation valves, not the 99p service valves for mains water pressure plumbing.

the two look similar but the full bore are a little more expensive but gota be worth it.

 

[chrishutt]

make sure you get "full bore" isolation valves

You don't need "full-bore" but you do need decent quality so that the spindle seals don't leak. The reduced bore on cheap isolating valves has a negligible effect on flow for most applications and if I could be confident that the spindle seals wouldn't leak I wouldn't hesitate to use them on CH systems.