Some plumbing / boiler questions ...

[YAPH]

3/4" BSP, standard for bath taps

You can make one (DIY - what more could you ask for? ;-))

Take a Speedfit 3/4" x 15mm tap connector and add a length of 15mm plastic pipe (preferably polybutylene rather than PEX, for flexibility).

[John Rumm]

If in the unlikely case you can just swap one rad for the other - then it would be very straight forward - turn off both rad taps, open the coupling a little at one end and drain the rad contents into a bowl, remove rad and replace, open taps, bleed as required[1].

However chances are you will need to alter pipework and taps for the rad (she probably wants nice chrome ones to match the rad as well!) For this you will need to drain some water from the system. This is exactly the same as you would do with a conventional system except there is no header tank and ballcock to mess about with.

Fear not, your halo will remain intact! ;-)

(the bit about foot pumps etc is nothing to do with "normal" operation of a sealed system but is to do with rectifying a particular type of fault that can happen)

I take you mean something like:

't see a push fit version - but if you need that, then just put a stub of pipe in the compression fitting and use a straight pushfit coupling on that.

[1] See Ed's description of filling and bleeding a sealed system here:

particular the section on "How do I refill the whole system when working alone?"

generally easier than doing the same on a header tank system.

[dennis]

Well you can argue about the term if you want, I am sure someone will join in if you want.

No I just don't like earths when there is a small chance of getting a shock because of them.

Say a towel rail becomes live.. this indicates that there is a fault in the towel rail and that the case *is not* connected to earth or the fuse would blow. Now all the other stuff like pipes are connected to earth and you get a

300V+ potential between them.. nasty shock.

Of course if there were actual physical earth points on the towel radiator rather than just the earth in the flex you might have a second earth to connect to the pipes but that's not likely as the fuse hasn't blown.

[Dave Plowman (News)]

That's nothing to do with CORGI. Much as they might want it to be or even imply it is.

Nothing new there. One claimed to my elderly neighbour that only they can install a cooker. Which in her case is electric...

Drilling some holes in a wall is gas related?

If it is a new boiler supply - rather than just connecting to an existing one - I'd hope the average CORGI wasn't let anywhere near it.

As regards DIY, no dispute. Just ignore all these greedy people trying to feather their nest.

[geoff]

That should exclude a fair number of CORGIs

CORGI is only concerned with safety, not competence,

Aren't CORGI losing registration to Centrica ?

This is a DIY group for people who DIY

Like me

[John Rumm]

The difficulty with the term (aside from it having no real meaning) is that is introduces confusion. Earthing and equipotential bonding are two unrelated concepts that reduce shock hazards in different ways.

Again, who mentioned earths? There is no requirement for supplementary bonding to be earthed.

Indeed. The (presumably electric in this case) towel rail's heating element should be earthed to ensure the supply is disconnected in the event of a fault.

Which is where the equipotential zone comes into play - eliminating (or at least reducing to a safe level) any potential difference should the fault not be cleared by other means.

If the pipes are capable of introducing a potential into the zone, they should also be bonded.

[John Rumm]

Drilling the holes is not, but what you stick through them (and how you do it) might be! ;-)

[Arfa Daily]

> Can't see a push fit version - but if you need that, then just put a stub

Thanks for the good advice, and confidence that it will be a straightforward job for me ! Son in law went to B&Q today, and got a pair of flexis that he tells me fit the taps directly at one end, and are 15mm push fit at t'other. Believe it or not, he says a spotty-faced erk in a B&Q teeshirt found these for him ...

All ok on the rad. The pipework will definitely need modding, so I guess a degree of draining down will be needed. Presumably, as it's an upstairs rad, so at the top of the system, if I shut off any other upstairs rads so that they cannot drain back into the upstairs pipework, then not much water will need to be removed ? Arfa

[Dave Plowman (News)]

If you're not sure of the condition, a full drain down and flush followed by new inhibitor will do no harm.

If draining down is difficult, now is the time to fit one of those combination lockshield valves and drain at a convenient rad - ie one close to an outside door.

[YAPH]

And even in a professional context soon won't be: I'm sure anyone who thinks CORGI are bad is going to *love* Capita.

If they're the difference between holding up a gas appliance and it falling off the wall, yes.

[Dave Plowman (News)]

I'd say the average DIYer who feels competent to fit a new boiler is likely to be more careful about fixings than the average CORGI.

It would be wonderful if CORGI membership was some guarantee of good workmanship. Unfortunately, it's not. Very few of these sort of trade bodies are - they're more concerned about their income from fees than maintaining any standards.

[John Rumm]

Yup, from the folks who brought us TV Licensing IIRC!

[John Stumbles]

What sort of trade bodies are you talking about? In the 'trade' (rather than 'profession') arena I can think of CORGI and maybe FENSA who are absolutely necessary for the tradesperson to purue their livelihood. With NIC/IEC there are alternatives (NAPIT, EIA). IPHE (or whatever they're called this month) is optional. I'm not even considering shop-window bodies like FMB.

I don't know how many useless members FENSA chuck out, but CORGI have a regular roll of dishonour of installers who they've deregistered for one reason or another.

Of course the threat of deregistration doesn't make a useless installer competent, but it does focus one's mind on doing the right thing when one might be tempted to cut corners.

[John Stumbles]

But one with the drain-off *outboard* of the valve - the ones with the drian between the valve and the rad are not a straight swap for the non-drain-off types.

[Dave Plowman (News)]

Didn't even realise there were two types. The one I've got was a straight swop. It came from Screwfix.

[Andy Wade]

John's absolutely correct and, to add to what he's already said, earthing and bonding should be thought of as quite separate concepts:

- earthing (of Class 1 equipment) is an /active/ protection measure that works by automatically disconnecting the supply to the faulty equipment;

- an alternative to earthing is the use of Class 2 ('double' insulated) equipment which is constructed such that the chance of exposed metal parts is close to zero. (The wiring regulations still require an earth to be available in a circuit feeding a Class 2 appliance, so that it can safely be replaced by Class 1 equipment.)

- Equipotential bonding is a /passive/ protection measure which prevents dangerous 'touch voltages' appearing between different items simply by connecting them together with low-resistance conductors of a size that won't overheat or rupture for any current reasonably likely to flow.

Things like water taps on plastic pipework (even with copper tails) are not going to become live on their own - so they don't need to be bonded. In the language of the wiring regs they are not extraneous-conductive-parts because they don't import a potential from outside the location.

This is a good example, an open-circuit circuit earth (CPC) being a fairly common fault.

With supplementary bonding in place there can be no significant touch voltage, whether or not anything blows or trips. If the bonding provides another path to earth, as it often will, the chances are that the overcurrent protection or RCD will operate as normal and isolate the fault. If the bonding is otherwise floating then you may end up with

230 volts on everything. With correctly done bonding there should be no risk of a fatal or serious shock, but people are likely to feel tingles when touching metal items and this will hopefully eventually lead to the fault being diagnosed.

Under the 17th edition regs the supplementary bonding can be omitted, but only if the main bonding is OK and all circuits feeding the bathroom are 30 mA RCD protected. In this case there is the potential (no pun ...) for a serious shock between the live towel rail and other (earthy) metalwork. However if the shock current is large enough to be really dangerous the RCD will trip and cut off the supply within a few milliseconds.

The regs allow the flex to be used as part of the bonding (you bond in the fused connection unit). Clearly the committee considered that the risk of an open circuit in the flex was low enough not to worry about. If you disagree there's nothing to stop you bonding to the rail itself.

[Roger Mills]

There are more than two types. There is the type referred to above

where the drain-off in in the tail - between the rad and valve - which increases the offset of the supply type. These may be impossible to fit to some rads where the threaded hole is inboard since the drain outlet may foul the rad as you screw it in.

Then there's the Screwfix type

- which have a fairly conventional drain-off fitting at the end, with the spout pointing downwards and a square bit to turn on the end. These can suffer from the same problem as other drain elbows etc. - where the washer sticks, so nothing comes out when you unscrew the end.

Finally, there's what I consider to be the best sort

- which have the drain plug *inside* the sideways-facing drain spout. You can unscrew and remove the whole plug (no washer sticking opportunities) with both radiator valves closed, and very little will come out until you open the radiator's bleed screw to let some air in. You control the flow with the bleed screw.

With all 3 sorts, with both valves closed, just the radiator is drained - but the pipework can also be drained by opening the valves.

[dennis]

But not in a normal house, using normal appliances as they metal case will always be bonded to earth.

Its actually two faults, the earth has been disconnected and the live insulation has failed, not actually very common.

As I said unless you are going to modify the appliance you are bonding to earth.

That would be the main bonding to where exactly?

So where do you not bond to earth within the FCU?

Like I said for domestic wiring it is bonding to earth, there is very little alternative if you have any sort of appliance.

And as I said if you want to discuss bonding in an industrial context it can be done.

We bonded huge amounts of metal together but we didn't use green and yellow earth cable to do it as it wasn't earth.

[Doctor Drivel]

"What it does is electrically tie together all accessible conductive parts (pipes, taps, electrical appliances etc) that could under fault conditions introduce a dangerous potential into the room. "

A rank amateur would look at that and not know what potential is. "Potential" needs a explanation at this point.

[Roger Mills]

Anyone who doesn't understand the word "potential" in relation to electricity shouldn't go anywhere *near* mains house-wiring!