# Plumbing sizes, i'm confused



## NorthernSky (1 May 2021)

i need a 25mm fibre washer for my shower. 25mm is the outside diameter
everything to do with plumbing seems to be in Inches. 
now to me 25mm is equal to 1"

why is this chart telling me 1" is 30mm? (seller on ebay)

is plumbing measured by the INSIDE diameter? 
in that case i'm going to need the 3/4" washer, bit confuddled 
also what is CTC


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## fossyant (1 May 2021)

Its 25mm, not 30.


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## Ian H (1 May 2021)

Imperial pipe was measured internally. Metric pipe is measured externally.


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## sleuthey (1 May 2021)




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## battered (1 May 2021)

As others have said, imperial pipe measurements are internal diameter of the pipe. You should try working in dairies, a 1" pipe fitting needs a spanner with an opening about 2" across .


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## neil_merseyside (1 May 2021)

As above about imperial measurements being internal diameter of pipes. For a shower union a bath tap fibre washer is usually needed (nom. 3/4") and that will measure a gnat's nudge under 25mm when new and dry, so will be around 25mm when splayed, and wet.


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## NorthernSky (10 May 2021)

hey folks, follow up to this. now i know the size i need can someone tell me what washer type i need.
i bought these from screwfix ( https://www.screwfix.com/p/arctic-products-flexible-tap-connector-washers-10-pack/5547j ) but they have a hard surface. when installed it just leaks.
it's like the intact washer is a softer type that has expanded and filled the gap?
i have this mixer unit. it's the washer that sits at the cold inlet on the wall
https://www.idealstandard.co.uk/products/catalog/showering/mixer-packs/a4741


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## neil_merseyside (10 May 2021)

Fibre washers are meant to swell and seal, but only the bit nearest the water actually swells the rest stays pretty much dry under compression from the joint, the joint isn't twisted/distorted is it?


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## NorthernSky (10 May 2021)

neil_merseyside said:


> Fibre washers are meant to swell and seal, but only the bit nearest the water actually swells the rest stays pretty much dry under compression from the joint, the joint isn't twisted/distorted is it?


thanks, yes i thought that what's meant to happen with them
the joint looks fine, i think it could more be the surface of those fibre washers i bought, they have like a shiny/hard surface before it gets to the fibre
was thinking i could sand that away and try it. failing that i may look some of the red fibre washers (similar to the one that's intact)
i take it fibre washers are widely common with plumbing? 
what about rubber washers, where would they be used more


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## neil_merseyside (10 May 2021)

Washing machine washers are 3/4" and rubber.


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## keithmac (11 May 2021)

Washing machine fittings contain the washer. A rubber washer will spread out sideways when squashed so not suitable for all applications.

Same as O rings.

Have you got a picture of the fitting?.


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## NorthernSky (12 May 2021)

yes will grab a pic when i can
ironically it's not leaking as bad just at the moment, since i've had it off and put it back on last time
will be worth having a spare though


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## Pale Rider (12 May 2021)

NorthernSky said:


> yes will grab a pic when i can
> ironically it's not leaking as bad just at the moment, since i've had it off and put it back on last time
> will be worth having a spare though



A couple of bodges/temporary/permanent fixes.

You could wrap a length of cotton fibre string around the fixing, or even cut a short length from a traditional dishcloth if you have none to hand.

Or you could create your own 'fibre' washer from a cereal packet.

Best to use a bit which isn't printed on either side, or use two pieces sandwiched, with the unprinted sides facing outwards.

Best of all, obtain the correct part, but this is the internet, the home of making things needlessly complicated.


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## Profpointy (12 May 2021)

Well worth buying a sorter box of mixed plumbing washers and spares for a fiver or so.

Anyhow my guess would be it's a washer for 3/4" BSP.


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## NorthernSky (16 May 2021)

finally got a picture of this.
intact washer from the hot side. it is quite thick but i think this is because it's expanded over time? doesn't seem to be made of rubber
if a rubber replacement worked i'd try that though



removed the mushed one



still struggling to get a replacement


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## DaveReading (16 May 2021)

NorthernSky said:


> finally got a picture of this.
> intact washer from the hot side. it is quite thick but i think this is because it's expanded over time? doesn't seem to be made of rubber



Fibre ?


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## classic33 (16 May 2021)

NorthernSky said:


> finally got a picture of this.
> intact washer from the hot side. it is quite thick but i think this is because it's expanded over time? doesn't seem to be made of rubber
> if a rubber replacement worked i'd try that though
> View attachment 588928
> ...


Washing machine washer?


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## neil_merseyside (17 May 2021)

The flat bit is mostly the washer as bought, the really swelled bit is the wettest bit and has swelled just beacause it isn't constarined, a small bit inboard of the fat bit is the bit that actually seals, from swelling up but being constrained it is only a tiny area and the crushed washer is mostly completely dry. Any cycling of that joint face from say dragging yourself out of the bath would have the wet area spread and eventually get a weep, but in general fibre washers do a great job, rubber washers squirm if overtightened, and they can't take out imperfections in the mating surfaces anywhere near as well.


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## NorthernSky (18 May 2021)

i couldn't find a thick enough fibre washer so ended up putting a rubber O ring around the thread and a rubber washing machine 3/4" washer in front of it. a few days ago and no leaks so hopefully all good.


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## classic33 (18 May 2021)

NorthernSky said:


> i couldn't find a thick enough fibre washer so ended up putting a rubber O ring around the thread and a rubber washing machine 3/4" washer in front of it. a few days ago and no leaks so hopefully all good.


Did you try using two fibre washers.


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## NorthernSky (18 May 2021)

classic33 said:


> Did you try using two fibre washers.


yeah, the fibre would not swell in any way though, i even submerged them overnight to see if they would take on water but no
they are a millimeter or so short of touching the threads so without the swelling to fill the gap the water passed through
the intact one is definitely an odd size, it's quite thick as you can see
oh, i also bought leather washers! they weren't on my radar until i spied them in b&q. was willing to try anything


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## newts (18 May 2021)

You can try 2 x 3/4“ fibre washers on both hot & cold. Clean the faces of the joint well before reassembly. Tighten each side a lilttle at a time to keep the torque even & the valve straight on the supply unions.


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