Wavy PEX B hot water pipe

[Jonlybonly]

Maybe I did something wrong when installing my Pex B pipes, but the hot water side seems to have some wild waves in it after a month. The pipes were straight 10 foot runs I purchased from Home Depot, all were secured with c clips nailed into the framing, same as the previous PB was.

Is this normal? Something to worry about? There are no kinks, but a general waving back and forth.

 

[Twowaxhack]

When pipes get hot they expand.

 

[Jonlybonly]

When pipes get hot they expand.

Yes, fully understood. But is this a concern? Should I take out some slack?

 

[Twowaxhack]

Post pictures of it

 

[Jonlybonly]

Post pictures of it

Crazy, it was much wavier before. My son was in the shower, so all that hot water must have been passing through the pipe. I guess this is normal?

 

[Twowaxhack]

it’s normal. Looks good and you agreed before someone deleted our posts.

Have a good day.

 

[CT-18]

I think pex B says supports every 30" or something in that area. If it is moving to much for your comfort you can always add more J hooks

 

[Jonlybonly]

Thanks everyone, I’m very new to Pex and definitely don’t want another flood.

 

[quinlanj98]

I did some calculations for a long PEX run in my basement and was surprised by the results. PEX expands at a rate of about 0.01% per degree F of temperature change. Assuming a wintertime basement temp of 55F and a hot water temp of around 120F, the max. resulting change of 65F could produce a pipe length increase of 0.01% X 65F = .65%. So a 10 ft run could change in length by nearly an inch. To accommodate that extra length, the pipe would need to bow out from a straight line by roughly 6 inches! (assuming you only clamp it at either end and that I didn’t screw up the math).

 

[Jonlybonly]

I did some calculations for a long PEX run in my basement and was surprised by the results. PEX expands at a rate of about 0.01% per degree F of temperature change. Assuming a wintertime basement temp of 55F and a hot water temp of around 120F, the max. resulting change of 65F could produce a pipe length increase of 0.01% X 65F = .65%. So a 10 ft run could change in length by nearly an inch. To accommodate that extra length, the pipe would need to bow out from a straight line by roughly 6 inches! (assuming you only clamp it at either end and that I didn’t screw up the math).

That’s interesting. I clamped it probably every 30 or so inches, which I thought was appropriate. I’m concerned that additional clamping will be more of a problem.

 

[Integrity Repipe]

What you’re experiencing is actually a common characteristic of PEX B when exposed to heat. PEX B has a higher thermal expansion rate than other types of PEX, meaning it expands and contracts more significantly when carrying hot water. This often results in the "wavy" appearance you're seeing. While it’s usually not a structural issue, excessive movement can put strain on fittings over time. To reduce this effect, allow for expansion loops or offsets rather than rigidly securing long runs. Also, using insulation around the hot water PEX can help minimize temperature fluctuations, which contribute to expansion.

 

[Jonlybonly]

What you’re experiencing is actually a common characteristic of PEX B when exposed to heat. PEX B has a higher thermal expansion rate than other types of PEX, meaning it expands and contracts more significantly when carrying hot water. This often results in the "wavy" appearance you're seeing. While it’s usually not a structural issue, excessive movement can put strain on fittings over time. To reduce this effect, allow for expansion loops or offsets rather than rigidly securing long runs. Also, using insulation around the hot water PEX can help minimize temperature fluctuations, which contribute to expansion.

Makes sense now, maybe I should go back in with expansion loops?

 

[Twowaxhack]

Makes sense now, maybe I should go back in with expansion loops?

Leave it alone, there’s nothing wrong with it.