Plastic or copper piping?

[david_uk]

Hi, I am in the process of renewing our bathroom. The hot/cold goes to the sink via plastic piping to an eaves access area behind the bathroom.

I'm changing the shower for a shower bath. The existing power shower is not being touched, but I need to supply hot/cold to the bath and sink. I plan on extending the sink hot/cold through to under the bath and splitting it one way for bath, one way for sink.

I'm moving the sink, and due to where I need to run plumbing am considering plastic flexible stuff. Behind the wall the sink will be on are two large cupboards. The construction is stud walling, and from the inside of the cupboards I can cut the plasterboard to gain access for the plumbing. I will replace the plasterboard with wood to provide access panels. I'm trying to do this with concealed plumbing as it is now.

Thing is, I know it will be easier to do this in bendy plastic with push fit joints, but I'm not sure if these are as reliable as copper with compression joints. Am I just being old-fashioned in preferring copper, or is the new and easy alternative equally suitable?

Subsidiary question re waste, if I bring the sink waste through the studwork to under the bath, is it permissible (or a good idea) to run the waste under the bath to join the bath waster after the bath trap? I don't want to bury plumbing under the floorboards.

 

[Softus]

Am I just being old-fashioned in preferring copper

Yes.

...or is the new and easy alternative equally suitable?

Yes. Some would say that it's more suitable for what you're doing.

There's nothing to stop you using the bendiness of plastic pipe with the old-fashioned-ness of brass compression fittings, if that's what takes your fancy.

If you use plastic push-fit, then I'd recommend Hep2o for its demountability. The mistake most often made with plastic pipe and plastic push-fit is to not follow the installation instructions. If you keep grime away from the fittings before using them, and if you look after the pipe, then it's difficult to go wrong. DO NOT allow the pipe to be scratched, gouged, grazed, or crushed, because any damage will comprimise the O ring seal. It is not possible to be too careful in looking after plastic pipe. Use a sharp and purpose-made cutter; the new Rothenberger slices are great for not distorting the pipe.

Subsidiary question re waste, if I bring the sink waste through the studwork to under the bath, is it permissible (or a good idea) to run the waste under the bath to join the bath waster after the bath trap? I don't want to bury plumbing under the floorboards.

Not sure what you mean by a "bath waster", but if the "r" was just a typing error then the answer is "yes", i.e. it is permissible, and fairly commonplace. A swept tee will help.

 

[david_uk]

Hi, and thanks for the reply. I'll go with the plastic push fit and follow the advice.

Couple more related questions.

The existing plastic pipe is white. No idea what brand. Can I assume that it's all standard, and if I get some 15mm pipe and fittings from a merchant it will fit to the existing pipework?

Also, I need to move the towel radiator. The plastic pipework for the heating system is in grey. Is this different in some way to the pipework used for hot and cold? Can I use one type of pipework and fittings to do the supplies to sink and bath and the towel radiator move?

Lastly on the topic of waste pipes (yes I did make a typo!) I'm thinking of using the type with push fit connectors that you glue together on the grounds that the bath waste goes under the floor and I will have to make a connection under there and this method is less likely to leak than push fit waste with compression coupling. Or am I incorrect on this one too?

Many thanks for all the help!

 

[Softus]

The existing plastic pipe is white. No idea what brand.

It's probably John Guest Speedfit.

Can I assume that it's all standard, and if I get some 15mm pipe and fittings from a merchant it will fit to the existing pipework?

The outside diameter will be 15mm, but each brand of pipe has its own inserts, which are essential, so if you cut the Speedfit then you'll need Speedfit inserts (aka sleeves).

Also, I need to move the towel radiator. The plastic pipework for the heating system is in grey. Is this different in some way to the pipework used for hot and cold?

If you buy plastic pipe ensure that you get barrier pipe. You can use non-barrier pipe if it's not for heating, but frankly it's not worth the saving.

Can I use one type of pipework and fittings to do the supplies to sink and bath and the towel radiator move?

Yes. I don't ever buy non-barrier, which eliminates the possibility of ever fitting the wrong stuff.

Lastly on the topic of waste pipes (yes I did make a typo!) I'm thinking of using the type with push fit connectors that you glue together on the grounds that the bath waste goes under the floor and I will have to make a connection under there and this method is less likely to leak than push fit waste with compression coupling. Or am I incorrect on this one too?

No, that's a good decision. BTW it's not called push-fit if you 'glue' it - it's called solvent welded.

 

[david_uk]

Hi again, and thanks for all the advice. I've now got it clear what I need to do.

One last question, if I drill a hole through the stud wall verticals to pass through the sink waste, am I compromising the structural integrity of the wall? There is a steel above this particular wall as it's part of a dormer, but I'm just concerned that I don't cause a problem. I'm an electrician by trade, and I am aware that where you can drill holes so as not to affect structural integrity is limited.

 

[Softus]

One last question, if I drill a hole through the stud wall verticals to pass through the sink waste, am I compromising the structural integrity of the wall?

The rules that you're thinking about wrt to drilling apply to joists, and I very much doubt that your studwork wall is providing any structural strength to the building, but without more information I can't tell you the effect of weakening the wall itself. It will probably just make it less rigid, so if it's a wall that's tiled for a shower, for example, then that should be avoided.

It largely depends on the dimensions of the timber that you're drilling a hole in, as I suspect you already realise. If you drill a 36mm hole (for basin waste pipe) in 47mm timber then there won't be much left, but if it's 72mm timber then of course there'll be lots left.