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## eracode

4234 posts

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#2163551 19-Jan-2019 08:41

eracode: The coefficient of thermal expansion of Marley PVC-U is 0.05mm/metre/°C.

So an eight metre run coping with, say, a 25°C temperature variation, will produce a change of 10mm.

I found the above coefficient by googling and the hit mentioned Marley by name.

Marley’s own site says:

“ ... uPVC has a relatively high rate of [thermal] change. The coefficient of thermal expansion for PVC is 7 x 10-5/°C. A handy rule is 7 mm change in length for every 10 metres for every 10°C change in temperature.”

Sometimes I just sit and think. Other times I just sit.

1719 posts

Uber Geek

#2163631 19-Jan-2019 11:28

eracode:
eracode: The coefficient of thermal expansion of Marley PVC-U is 0.05mm/metre/°C.

So an eight metre run coping with, say, a 25°C temperature variation, will produce a change of 10mm.

I found the above coefficient by googling and the hit mentioned Marley by name.

Marley’s own site says:

“ ... uPVC has a relatively high rate of [thermal] change. The coefficient of thermal expansion for PVC is 7 x 10-5/°C. A handy rule is 7 mm change in length for every 10 metres for every 10°C change in temperature.”

That means 13.4 mm movement for the 8 m at say 24 degrees change (but in fact we probably get a season variation of 26 or 27 degrees, it can get a few degrees C below 0) if my math is right. .00007x8x24x1000

I am guessing the reason for having the expansion/contraction around the downpipe is because the downpipe is fixed.... so you want the movement happening to be on either side of it, vs putting the expander section say in the middle only. Which means it would be better to replace the dropper piece, not just add an expander section (unless you stick it on the long side just before the dropper)

1719 posts

Uber Geek

#2163710 19-Jan-2019 14:12

So see here in step 9, if the run is longer than 12 m replace one of the joiners with an expansion joiner. In previous steps you are still using an expansion dropper.

Quote:
Use spouting joiners and Marley MCS® solvent cement to connect lengths of spouting as necessary. For long runs over 12 metres replace one of the spouting joiners with an expansion joiner to provide further expansion allowance.

From https://www.marley.co.nz/knowledge-hub/diy-nation/spouting-systems-2/install-spouting/

This suggests to me that it's normal to use an expansion dropper for runs shorter than 12m with additional ones as required.

I'll call Marley on Monday and see what they say. I can't find anything that says how short a run has to be to use a non expanding dropper. All the install brochures seem to use expanding ones.

Also on this diy vid guy uses an expansion dropper but says since it's under 12 m he doesn't need to add another expansion joiner.

Also, this guide is for stratus and not classic but it does say (twice) droppers without expansion are not to be used in over 2 m of length. It also says any section over 4 m without an expansion dropper (because there are no downpipes there) on either end should have an expansion joiner in between.

1719 posts

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#2164767 21-Jan-2019 14:06
One person supports this post

Update! Marley says less than 10 metres does not require an expansion outlet. Yay.

## eracode

4234 posts

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#2164771 21-Jan-2019 14:14

JayADee: Update! Marley says less than 10 metres does not require an expansion outlet. Yay.

Your young fellas do know their stuff!

Sometimes I just sit and think. Other times I just sit.

1719 posts

Uber Geek

#2164779 21-Jan-2019 14:22

eracode:
JayADee: Update! Marley says less than 10 metres does not require an expansion outlet. Yay.

Your young fellas do know their stuff!

Yup. And they have done an excellent job on the re-roofing too. I wonder if they like beer. Or iced tea?

Edit: I am not a drinker. What kind of beer might they like?

## Technofreak

3610 posts

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#2164828 21-Jan-2019 15:51
One person supports this post

JayADee:  What kind of beer might they like?

Cold

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