External Ducts with smooth joints to prevent water pooling

[sheeners]

Hi

 

I'm looking for ducting options to external vents (exhaust and fresh air intake). 

 

Given that these should be designed such that no potential condensation can pool, I'm keen to rule out that water pools in joints. It seems the only option for this would be if socket joints have  male/female coupling and ends point downhill. 

 

I'm curious to hear other opinions. 

 

If I'm right, then most preinsulated pipes (e.g. Aerofoam, Blaufast) are disqualified.

 

Thoughts?

[Mike]

It's a good point. From memory, the surface tension of water droplets requires a hole >6mm diameter for the drop to enter. Foam pipes will join together closer than that, so the risk of individual drops entering the joint is low, so long as they can run down the duct and not accumulate, so I'd say that the risk was low. Low enough for me not to worry about anyway

 

Edited Sunday at 14:51 by Mike

[Nickfromwales]

Not a real world issue afaic. 
 

I’ve fitted loads of systems, foam and rigid steel, and nobody’s ever reported standing water to be an issue.

 

Constant airflow means these just suck or blow themselves dry, but I do angle the last bit of duct downhill before it gets to the external facade.

[Nickfromwales]

Fitted these on a good few jobs where driven rain was expected to be a factor to mitigate against. 
 

 

These were for 180mm ducts. 

[Nickfromwales]

And before the crowd mobs me, that was the size of the plant room and the designer confirmed that those being close was a non issue (considering these can be in one dual terminal). 

[JohnMo]

On 14/12/2025 at 13:40, sheeners said:

I'm right, then most preinsulated pipes (e.g. Aerofoam, Blaufast) are disqualified

Not sure what you mean here? Disqualified from what?

[Nickfromwales]

2 minutes ago, JohnMo said:

Not sure what you mean here? Disqualified from what?

Out of the running for being used I guess. 
 

Kinda reduces options to….?