Changing an outside tap

[mo]

I wnat to change an outside tap so I can screw a hose onto it.

Someone suggested that I can just unscrew my old one and screw a new one on.

From what I can gather it must be a compression fit tap and 15mm seems to be standard so I could buy one of these

is also one with a check valvle but not sure what that offers?

have read a bit on compression fittings. If I am screwing that onto my existing pipework will I need new oens of these? the 2 bits on the left

or particlarly the bit in the middle which I understand needs to be repalce with each new fit?

you can see screwfix only provide the tap but not the other bit you screw and seal it with.

[Harry Bloomfield]

mo brought next idea :

The check valve built-in or inline with the feed pipe to the tap is a requirement. They are a one way valve to prevent foul water being syphoned back via what ever hose you fit, or if the hose end happens to fall in a pond - back into the mains.

Probably not, but I seem to remember there is a fibre washer between tap and its socket - you may need a replacement for that.

[Roger Mills]

No, you *don't* need a compression fit tap - you need one which has a male

1/2" BSP thread which screws into the fitting on the wall.

That is *not* a compression fit tap. It has the right type of thread for your purposes.

A check valve stops water flowing the wrong way - and thus prevents dirty water from getting into your mains supply, as could otherwise happen if there were a supply failure while you had a hose from the tap dipping into (say) a pond. It's a good idea (may even be mandatory?) to have a check valve when using an outside tap.

You shouldn't need any of that. You should be able to unscrew your existing tap from its fitting on the wall (which will probably be similar to

and screw the new one in. Turn the water off at the stoptap first, of course!

You *will* need to seal the threads, using either lots of PTFE tape or some Boss White and hemp. The latter is messier, but you're more likely to be able to get the threads to go tight when the tap is upright.

[mo]

"Roger Mills" wrote in news: [e-mail]:

Thanks - it is described as compression i nthe description?

So I will just buy that one and screw it on then wrap with PTFE tape

cheers

[Bob Eager]

NO - you need the one with the check valve, to be legal (and to avoid possible contamination of your water supply).

[Derek Geldard]

Same type? If so yes.

with a "male iron" backplate screwed to the wall.

[www_diynot_com]

It can be a requirement of the water board so as to prevent contaminated water (from watering cans, hosepipes, whatever) being drawn back into the supply pipework.

As a rule only the copper / brass "olive" needs to be changed. These are very cheap and are generally bought by the bagfull / bubblepack.

Be aware that a compression fitting with the backnut and olive removed looks superficially the same as a male iron fitting, but by golly it's not the same.

Best advice is to replace like with like and replace any olives that get disturbed.

Derek

[John]

"So I will just buy that one and screw it on then wrap with PTFE tape"

No!

PTFE is used to seal threads where the thread is intended to form a seal. It isn't needed in a compression fitting where the olive uses metal to metal contact to form a seal. The thread is to pull the parts together.

[Frank Erskine]

In this case the 'compression' probably means that it has a conventional washer which compresses when you turn the tap off, rather than a 1/4 turn type.

[The Medway Handyman]

You can use either tap, the latter has a non return valve to stop back syphoning - water board paranoia. It does comply with the regs though.

For either you need

[mo]

"The Medway Handyman" wrote in news:JM%Dn.1061807$ [e-mail]:

what will i do with that?

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there seems to be some confusion on here about whether or not that tap is a compression tap and whether i use PTFE tape

[Roger Mills]

That - or some female threaded equivalent - will already be there with the existing tap screwed into it. He shouldn't need to replace that.

[Roger Mills]

Yes, but this tap doesn't use any olives - it seals on the 1/2" BSP thread.

Any reference by the OP to "compression fittings" is totally erroneous.

[Roger Mills]

Is it? Where? I didn't see any reference to compression fittings.

Not quite! You wrap the tape round the threads of the tap *before* you screw it in, so that the tape ends up *inside* the wall fitting between the male and female threads, thus effecting a seal. Wrap it clockwise, when looking from the open end of the male thread towards the tap body, otherwise it will get forced out when you screw the tap in.

IMHO, Boss White and hemp is preferable in this particular situation. If you use PTFE tape, unless you're lucky (or skilled, which sounds doubtful!) you'll end up with a situation where the tap is rotated to a funny angle - and not upright - when the threads are tight.

[Harry Bloomfield]

It happens that Roger Mills formulated :

Wrap a fairly even layer of the tape around the entire length of the threads of the male thread - the tap. The tape is very thin and very delicate, if you have not come across it before. Just wrap it tight enough that you can clearly see the shape of the thread, try 2 or 3 layers and add more if it doesn't tighten. One roll should allow you plenty of practise.

[Heliotrope Smith]

"Roger Mills" wrote in news: [e-mail]:

Hemp and Boss White have long since been completly illegal on anything connected with potable water.

Use only PTFE tape or Loctite String. Whith Loctite you can always turn back a half turn or so to get the fitting (tap) in the required position.

--- news://freenews.netfront.net/ - complaints: [e-mail] ---

[Dave Osborne]

Just to be clear on the check-valve issue:

1. It is a legal requirement to have a backflow prevention facility on an outside tap.

See: Statutory Instrument 1999 No. 1148

The Water Supply (Water Fittings) Regulations 1999

Schedule 2 Sec. 2 applies.

The WRAC (as was and through this document):

at: (See G15.20 on page 40) that for new installations a double check-valve located inside a building and protected from freezing provides suitable protection to incoming mains to prevent backflow from garden installations (including hosepipes).

For existing installations, G15.21 applies:

G15.21 Where, in existing house installations, a hose pipe is to be used from an existing hose union tap located outside a house and which is not provided with backflow protection, either:

a. the existing hose union tap should be provided with a double check valve located inside the building; or,

the tap should be replaced with a hose union tap that incorporates a double check valve (Type HUK1); or,

a hose union backflow preventer (Type HA) or a double check valve should be continuously fitted to the outlet of the tap.

(a) is the best option, as you don't have a problem with freezing the valve and wrecking it.

HTH

[The Medway Handyman]

OK. Back to basics. There is no such thing as a compression tap AFAIK.

The tap screws into the female thread on the wallplate elbow, the wallplate elbow is fixed to the wall using the holes on the triangular plate with screws & plugs. Outside taps don't fit directly onto copper pipes.

The copper pipe supplying the water connects via the compression fitting on the pipe.

[Roger Mills]

Says who?

If not boss White, you can get Hawk White suitable for potable water, such as

I don't suppose that the OP is going to *drink* water from his outside tap!

[mo]

Thanks all

I bought the screwfix tap with the valve.

Simply unscrewed the old tap.

PTFE tape on the thread of the new one and it screwed onto place - works fine.

I didn't need the wallplate as the old one sufficed.

Did get confused as I bought a plastic hose pipe thread connector and was confused as to why it didn;t fit on. But the tap comes with 1 half of the plastic fitting so I had to throw away half of the plastic fitting!

i.e the tap already came with the black bit here: