Bit of a problem - draining gravity system

[Hallsy]

When I pulled out my old bathroom on thursday ready for platering, etc I capped all the pipes off with isolation valves.

Now that we are starting to put things back and working out where things are going, I'm going to need to move/modify pipework.

Is there anyway of draining the system direct from the tank? Obviosuly before I just left all the taps on until it had drained, but can't do that now!

Only other thing I thought of is putting a bit of pipe in one of the valves and attaching a piece of hose to it, feed that down the soilpipe then open the valve. Should work OK shouldn't it?

Other thing, I'll be needing to do some soldering under the floor, but in my experience as you've drained the system via a tap, etc the re is still a lot of water in the pipes.

How is it best to get rid of the remaining water before soldering?

 

[Fluffster]

You can get a lenght of hose put it in the cwst then suck on the pipe to get the water flowing placing the end of the hose in a suitable recepticle lower than the tank and it will drain nicely, then clean any muck from the base of the tank.

Water in pipes would have to be blown out thoroughly I usually apply some heat to remove any residue, it is not a foolproof method however so maybe a commpression fitting?
Pete

 

[John_D]

do you have a hot tap in the kitchen? run that

a suggestion I once read said plug the pipe with bread to suck up the water and flush thoroughly you can get the toasty smell from open ends
are you on mapp gas? the high temperature can solder with some water about, be careful they can also make other fires and burn off the flux

 

[gas4you]

I take it that there is not a drain cock on the bottom of the cold fill to the cyl where it joins the cyl?

If not once drained I recommend you put one there for future use

 

[Hallsy]

I take it that there is not a drain cock on the bottom of the cold fill to the cyl where it joins the cyl?

If not once drained I recommend you put one there for future use

Aha, hadn't thought of that!! Under a load of old clothes, there it was!!

So draining from here should get most of the water out, then remaining water in pipes I want to solder I'll have to siphon out or soak up.

Don't think it's MAPP gas, it's my old chaps and he's had it a little while.

I would use compression but as it's under the floor I'd rather use solder.

Could go one of two ways considering this is my first time at pipe soldering!!

 

[gas4you]

Blow through pipes to remove water, make sure the copper is wire wooled cleaned and use flux. Don't overheat joint and remember to use lead free solder for domestics

 

[Softus]

Only other thing I thought of is putting a bit of pipe in one of the valves and attaching a piece of hose to it, feed that down the soilpipe then open the valve. Should work OK shouldn't it?

Yes, and none of your other options is as easy.

However, tip: if you're intent on opening the DHW cylinder drain cock, don't expect it to reseal without replacing the washer.

Other thing, I'll be needing to do some soldering under the floor, but in my experience as you've drained the system via a tap, etc the re is still a lot of water in the pipes.

...which one good reason not to solder under the floor.

How is it best to get rid of the remaining water before soldering?

I wouldn't bother - as long as the pipe is in good enough condition I'd use either compression or push-fit fittings.

 

[Hallsy]

Really? The floor will be tiled over so I was thinking along the lines of using a more permanent connection, although I've never had a compression fitting fail.

The pipes are pretty close together under the floor so compression may well be easier, just thought it was bad practice under a floor.

Thanks for the tip with the drain cock, I'll leave that and just use a hose on the end of a valve.

 

[Softus]

Really? The floor will be tiled over so I was thinking along the lines of using a more permanent connection, although I've never had a compression fitting fail.

Nor me, as it happens, but that faint drumming sound you can hear is the sound of hundreds of people rushing to tell you I'm a fool/cowboy/amateur, and that all plumbing in the entire world has to be end-feed soldered copper.

The pipes are pretty close together under the floor so compression may well be easier, just thought it was bad practice under a floor.

Just weigh up the risks - a compression fitting will leak only if poorly fited or sufficiently vibrated or wiggled. If they ever leak then one can usually get access from underneath. If you can't do that, then maybe you'll choose to solder. But if the pipework is moist, or dirty, then you might struggle to make an adequate soldered joint, and it takes a little dob of flux, sitting on old copper, for a few months, for a pinhole to develop.

It it were me, either on a job or in my own house, I'd use push-fit for ease and speed, or compression, in which case I'd thoroughly clip the pipework to prevent movement.

 

[Hallsy]

OK, thanks for that - I'm currently weighing it up