Over flow problem

[Biggal5]

Hello,
New to this site so be gentle! I'm looking for a second opinion. Just installed a low profile basin for a customer. £200+ for basin so no trade standard. When the customer washes hands with soap suds come back through the built in overflow? Had a bottle trap on it first, then after problem put a P trap on... Still back flow of suds? Waste pipe is 32mm for about 4" then 40 all the way. Water flows down plug hole perfect?? Is this my plumbing problem or you think could be design fault? Seems odd as reputable name??

Any help appreciated

 

[Howsie]

Have they tried a different brand of soap?

 

[jtsplumbing]

Sounds like faulty Basin ! What make is it ? probably paid over the odds for a Chinese import.

 

[Biggal5]

Thanks for your replies. I didn't want to be cheeky and say change your soap but was thinkin that!

make us Laufen? (Funny enough they are Chinese)

they seem to want the problem to be mine as they don't want to pay for redoing pipe work etc.?

 

[Rickster123]

Wait till they turn their backs and then pump a tube of silicone into the overflow. Sorted!