Some plumbing / boiler questions ...

[Arfa Daily]

A few weeks ago, I checked on here as to what was the situation with regard to doing work on my daughter's bathroom water, as she had one of those new fangled boilers with lots of pipes connected to it. The general advice was that if the power was cut, and the water input was shut off at the rising main stop-tap, I could just go ahead and disconnect her bath and so on, and then just restore water and power at the end. Well, today, it just got a bit more complicated. She has now decided that she wants the radiator changing to one of those 'ladder' types as well, so my new question is, given that the boiler will be off by virtue of the input water and power being off, is there anything else I need to do either before disconnecting the old radiator, or after hooking up the new one, apart from bleeding it, obviously? From memory, the boiler is an Alpha CB24X.

Being a daughter, she has total faith in her dear old dad, but I must confess that I am not looking forward to this job, as I have never worked on anything other than a traditional system with indirectly heated hot water in a storage tank, and the talk I see on here of pressurising modern systems with footpumps and so on, puts me off a bit.

The taps for her new bath have the large size of inlet, but the pipes going there are 15mm. Also, the space is very tight behind that end of the bath, and there are also a pair of 15mm pipes tee'd in to feed an existing shower. To make it all a lot easier to couple up, I would like to pre-assemble the taps onto the bath, and come off them with 15mm flexis with a push-fit remote end. Is there a flexi made, which has 15mm push collar at one end, and 22mm tap connector at the other, or am I going to have to fit a 22mm connector, followed by a 22 to 15 reducer ? Or is there a threaded adaptor available ? Or what is the recommended way of getting from 22 to 15 via a flexi tail ? All useful advice appreciated before Saturday, when it all begins ... :-\

Arfa

[A.Lee]

It is doubtful that the new radiator will be a straight fit onto the old taps. So you'll need new taps as well as some 15mm pipe, as the new rad is likely to be thinner in width, hence the pipe will need extending. Drain off the central heating water firstly. You should need to empty the system, just to drop the level below the lowest point you are going to work on. To help, turn off all of the other raditator valve before commencing, as you wont have to wait for them to drain then. Put some inhibitor in when you refill.

Loads of different flexis are available for pipe to tap connections. Get a Screwfix catalogue, or look at their website for the various options.There should be available what you require in push-fit, though i have never bought push fit - I think compression are better for such places.

Also be prepared at have to adjust the waste outlet, not all baths have the waste in the same place. Alan.

[Dave Plowman (News)]

In terms of working on it there's little real difference between a pressurized heating system and an open one. Basically the header tank is replaced with a pressure vessel (usually part of the boiler assembly) which should need no attention after a drain down and refill. The filling point is usually at the boiler and needs to be connected to a mains pressure supply - but this should all be in place and pretty obvious. One real benefit is the mains pressure means far less chances of airlocks. Once the system is filled and bled the water supply should be turned off and disconnected.

[RobertL]

Have you checked the power of the new 'ladder type' rad? These fancy rads often give much less heat than the normal type. her bathroom will be colder. Robert

[RobertL]

On Sep 24, 2:31=A0am, "Arfa Daily" wrote: ...

also, it is really true or just and urban myth that you need to be corgi registered to work on the rads connected to a combination boiler?

Robert

[dennis]

Its true if you are running the gas through the rads. But then you will be ejected from Corgi for doing stupid dangerous things, maybe ;-)

Is it true you have to be an electrician to work on the rads if any of the pipes go through a part pee restricted zone?

[Tim S]

dennis@home coughed up some electrons that declared:

I've given up trying to interpret some of the legal stupidities.

What is actually important is if the plumber finds any equipotential bonding straps, he should put them back after finishing his work. This is not to my knowledge a notifiable work, so as long as he can do a clamp up competently...

Technically, testing the bond is a good idea, but providing the pipes are shiney, clean and bare and the clamps + wire go on correctly and tightly, there's not a lot that can go wrong.

What is an interesting question is what happens if the plumber just replaced a load of metal pipe with plastic. That's a bit more of a can of worms.

Cheers

Tim

[Dave Plowman (News)]

You don't need to be CORGI registered for *any* DIY in your home. Including gas work.

[dennis]

Or if they are silly enough to put PTFE tape on compression joints?

I am one of those that doesn't think taps should be earth bonded BTW. If there isn't a path to earth its much harder to get a fatal shock than if the plumber provides a low impedance earth.

[mark.hannah]

I hadn't considered that this could cause a loss of electrical continuity on pipe-work! So do you mean that PTFE tape should not be used at all on compression joints?

I would have thought that there was still enough metal-to-metal contact in a compression joint to maitain continuity?

Mark.

[John]

I thought it was very bad practice to use PTFE on compression fittings. The seal is done by the olive gripping the pipe and being located in a very clean conical fitting. The thread has no role in sealing - so PTFE has no role.

[Arfa Daily]

Interested to know Dennis, how PTFE tape on compression joint threads, might compromise the integrity of earth bonding ??

Arfa

[Dave Plowman (News)]

Those who do use PTFE on compression fittings tend to wrap it round the olive. Not much point in putting it round the thread as this doesn't provide any seal.

[The Medway Handyman]

Agreed from the sealing aspect, but its a very useful lubricant - makes doing up the fittings easier.

[The Medway Handyman]

Give him time, he will think of something.

[dennis]

I didn't say threads. I have undone joints and found PTFE tape around the pipe and olive.

[John Rumm]

There is no role in the sealing, but it does help lubricate the thread and hence makes it easier to tighten smoothly.

[YAPH]

Yes, if they're done properly with PTFE over the olive rather than on the thread of the fitting which the nut screws onto (where it is absolutely useless since this threaded joint does not provide the seal, only mechanical compression).

Actually neither PTFE nor any other jointing material should be necessary on compression joints, made with unblemished pipe and new fittings in clean conditions: it's when one's obliged to re-make joints that something's often helpful to get it to seal, and here a couple of turns of tape round the olive or a smidgeon of Boss White/Green/Universal (according to application) can be used.

[John Rumm]

No such thing as "earth bonding"

ISTM you are misinterpreting the purpose of equipotential bonding:

[YAPH]

But, just to go over it again, you *do* have to be 'competent' (in the words, undefined, of the Gas Safety Installation & Use Regulations).

Where one draws the line wrt non-DIY work seems to be a matter of interpretion. IIRC in a recent article CORGI were trying to claim that

*all* connections to a boiler were the domain of registered installers. Certainly all gas pipework and flueing is 'gas work' and there's a good argument that hanging a boiler is too, but equally if an installer isn't qualified to do electrics then a non-CORGI sparks may reasonably be expected to be allowed to make electrical connections to it and do cross-bonding if needed. Who does CH, hot and cold water and condensate pipework then has the making of a '70s-style who-does-what dispute :-)