Egg shaped pipes

What I learnt on Monday is that some precast producers make concrete ovoid pipes. My fist impression was "what's the point in using such an odd section?". As fas as I know they are very rare in Spain. After flicking through an old book on hydraulics I realised that the ovoid pipes have better velocity characteristics at low flow than the equivalent circular pipes and this feature implies two great advantages:

• Better self cleaning and less risk of blockages.
• Reduced costs of excavation.

The moral of this post is: be reluctant and never trust traditional solutions blindly.

Pic: Ovoid pipes, around 100 € per metre.