I'm currently renovating my kitchen and as part of this I have run some PEX pipe for the hot water, there is a length of about 4M going across the wall. I have pipe clips about every 18" or so. Anyway It all works fine and looks nice and neat until I run the hot water, then the pipe flex's and becomes quite 'wavy'. Is this normal? Should I have more clips. The pipe will eventually be hidden so it dosen't matter what it looks like, but it just suprised me how wavy it becomes with the hot water running.

How do you mean wavy, flaps about or drapes, and does it straighten again.

How hot is the water

Stiff lagging would help.

What is the brand make/model.

Your bit's should be in Monday hopefully.

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It drapes and yes it straightens again. The water is about 65C. I got the pipe from B&Q think it says 'QUAL P-EX' on it and says it's good for 92C. The fittings are JG Speedfit. It's clipped to the wall with the white, plastic, single screw, C clips. I'm fairly sure it's nothing to worry about, but it did suprise me.

I'm surprised it drapes at that temperature.

Should be ok provided it doesn't kink where it's fixed.

Sounds like you have a cheap own brand.

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I think so too, gonna put a few extra clips in just to be sure.

I added a few more clips, but still not happy with the way this pipe is flexing, I think I am going to get some speedfit pipe and have another go at it.
Unless someone can tell me this is normal.
Here's a cold and hot pic


Hot


Cold

Probably normal, it don't look too bad now.

Strange it straightens up when it goes cold

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Should Pex tube be used like that?

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Yes Mooncat, shouldn't be a problem

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Is there a problem with it? Should I be using something else for hot water?

It expands when hot and is it gets longer squeezes out between the clips?

Thought the coefficient of expansion for copper was high but as that looked so ridiculous, I looked it up and for plastics it can be 4X more! more reason to use copper.

There is a time and place to use each material, plastic isn't all bad!

Plastic can have a reduced cost of installation as you don't need special tools (soldering, pipe benders, etc) and quite frankly, is simple to DIY.

There are also occasions where plastic is a sensible choice - like my bathroom and some parts of my stupid shaped house. To install copper would have took the best part of a week just for a shower, bath and sink (5 walls, above three different rooms and not much in the way of access to joints/bends - plastic was super easy to work with and does exactly the same job.

I'm certainly not going to lose any sleep over unseen runs.

BG

The only think I could think of was aluminium railings and railway tracks. It is the way that the pipe goes up and down between the clips that gives it away. When I started reading the thread I thought it will be getting hot and "melting" so it should go lower between every clip.

To the OP. Using more clips to force the pipe to remain straight will exert more pressure at each end of it (assuming it can slide in the clips)... or it will produce a bigger curve where it finds the weakest clip.

making plastic pipe look neat for show is an a total pain in the arse. the best way I have found is allow slack in the bends..ie the expansion is taken up in the corners where it turns 90 degrees. also loads and loads of pipe clips

every 300mm like this is your best bet:

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