[Steve Weatherley]

I am looking at updating my static system with new filters, tubing and RO. I would like to use the same size tubing throughout if this is possible (1/2" outer diameter).

The problem I have is that I don't have a great understanding of all the connectors and adapters as there seem to be so many different ones. Some are BSP, some are NPTF......and then there are also others. Some tubing is measured in outer diameter and some is inner diameter.

The only thing I do seem to understand is that the John Guest tubing is measured in outer diameter.

Can someone start by describing the different between BSP and NPTF?

[andyM]

BSP (British Standard Pipe) is a British pipe fitting thread which has been around for donkeys years.
NPTF (National Pipe Taper Fuel) is an American fitting thread.
If I had a choice I would probably go for BSP fittings as probably more easily available.

[Spruce]

BSP and NPTF are very close to each other pitch wise so in plastic housings can be interchanged but using the same threads is best where you can source them.

We have a 4040 r/o with NPTF threads and used NPTF fittings where available.

Here is the fitting for 1/2"
http://www.osmotics.co.uk/products/John-Guest-Straight-Adaptor-1%7B47%7D2%22-NPTF-Thread-1%7B47%7D2%22-Tube.html

We also bought elbows
http://www.osmotics.co.uk/products/John-Guest-Stem-Elbow-1%7B47%7D2%22.html

and converted some of these to standard 1/2" hose
http://www.osmotics.co.uk/products/John-Guest-Tube-to-Hose-Stem-1%7B47%7D2%22-ID-Tube-to-1%7B47%7D2%22-Stem.html

The prefilter housings are also NPTF but used BSP fittings to fit pressure guages.

We also used a 1/2" BSP barrel nipple to a 1/2" BSP gate valve for controlling waste output screwed into NPTF female socket in the r/o housing.

As is standard plumbing practise, all threads were wrapped in PTFE plumbing tape to seal the threads. The fitting instructions warned against using other 'chemical' sealing compounds. I did have one BSP female to NPTF male fitting that just wouldn't seal, so in desperation I mixed up some araldite and 'glued' it in - it hasn't leaked since. My feeling was that if the glue did damage the fitting, it would be easily and cheaply replaced.  

[andyM]

I don't think i've ever used NPTF fittings (knowingly), so I don't know a lot about them.
But from what i've read they are a tapered thread fitting which supposedly do not require a sealant tape or compound because the taper provides a mechanical leak free fitting.
Did you find that to be the case Spruce?
There are also BSP tapered thread fittings available.
 

[Nameless Drudge]

You`ll never really know,sometimes when everything is finally put together you might have a moment of clarity and realise the simplicity of it all, but it doesn`t last and you have to start again next time,guessing,ordering the wrong bits,over-ordering etc.
Eventually though you`ll have a plumbing war chest and be able to adapt a 6mm hose tail to Hozelock with only 9 intermediate joints,11 jubilee clips,2 rolls of ptfe and a combined weight of only 10kg.

[andyM]

You`ll never really know,sometimes when everything is finally put together you might have a moment of clarity and realise the simplicity of it all, but it doesn`t last and you have to start again next time,guessing,ordering the wrong bits,over-ordering etc.
Eventually though you`ll have a plumbing war chest and be able to adapt a 6mm hose tail to Hozelock with only 9 intermediate joints,11 jubilee clips,2 rolls of ptfe and a combined weight of only 10kg.

...................and more copper than the local Gypsie Mafia 

[trevor perry]

You`ll never really know,sometimes when everything is finally put together you might have a moment of clarity and realise the simplicity of it all, but it doesn`t last and you have to start again next time,guessing,ordering the wrong bits,over-ordering etc.
Eventually though you`ll have a plumbing war chest and be able to adapt a 6mm hose tail to Hozelock with only 9 intermediate joints,11 jubilee clips,2 rolls of ptfe and a combined weight of only 10kg.

[Window Washers]

You`ll never really know,sometimes when everything is finally put together you might have a moment of clarity and realise the simplicity of it all, but it doesn`t last and you have to start again next time,guessing,ordering the wrong bits,over-ordering etc.
Eventually though you`ll have a plumbing war chest and be able to adapt a 6mm hose tail to Hozelock with only 9 intermediate joints,11 jubilee clips,2 rolls of ptfe and a combined weight of only 10kg.

haha ^^ isn't that the truth

[Nameless Drudge]

Then there`s the hours spent staring at little plastic bags of shiny metal in B and q,bringing a connector with you to compare and wondering if security will think you have just nicked it.Then you think those 2 together would do it,look at the cost and think,"i clean 2 houses for that".

[Washing Windows]

You`ll never really know,sometimes when everything is finally put together you might have a moment of clarity and realise the simplicity of it all, but it doesn`t last and you have to start again next time,guessing,ordering the wrong bits,over-ordering etc.
Eventually though you`ll have a plumbing war chest and be able to adapt a 6mm hose tail to Hozelock with only 9 intermediate joints,11 jubilee clips,2 rolls of ptfe and a combined weight of only 10kg.

Then there`s the hours spent staring at little plastic bags of shiny metal in B and q,bringing a connector with you to compare and wondering if security will think you have just nicked it.Then you think those 2 together would do it,look at the cost and think,"i clean 2 houses for that".

Fabulous... thanks for actually making me laugh out loud!

After spending and entire weekend trying to get my head around RO systems and their various components you have summed up my feeling perfectly.

Duncan

[Spruce]

I don't think i've ever used NPTF fittings (knowingly), so I don't know a lot about them.
But from what i've read they are a tapered thread fitting which supposedly do not require a sealant tape or compound because the taper provides a mechanical leak free fitting.
Did you find that to be the case Spruce?
There are also BSP tapered thread fittings available.
 

In theory you are correct as the taper should seal the threads together as they are tightened up. However in reality, these fittings are mass produced and will have larger tolerances in mass production – threads being machined at great speed.
Even many years ago before PTFE tape was common, the practice of sealing fittings was with a fibrous thread (like frayed cotton). It would swell when it became wet and would seal those threads in a short period of time.
PTFE tape has just brought this process into the modern age. I don’t think there is any plumber out there who wouldn’t use thread sealing tape.