Back Flow Issue

[Jimmeh]

Evening all!
Went to look at a job today, customer has fitted a kitchen sink which backs onto a wall that has a shower on the other side. Its a low level tray and the waste has a poor fall (very minimal) and is very very difficult to get to. When the sink is full and empties it backflows through the shower waste into the tray. But if the flow is just straight from the tap down the sink this does not occur. How can i overcome this with minimal work to the waste pipe, I know it might sound daft, but restricting the flow from the sink waste may work right? Or would a crazy idea like putting a HepVo trap into the waste before the sink waste enters the waste pipe and after the shower prevent a backflow?

I only say this as the waste pipe is sooooooooooooo hard to get to, its a real nightmare and I could JUST get something as big as a HEPvo into it as there is bugger all room for me to even get me hands in!

 

[Billy Bob Bob]

what about one of these
McAlpine 40mm 1.5" Non Return Valve T28M-NRV | eBay

 

[Jimmeh]

havent seen that before gas man, same principal I suppose? Self sealing system inside?

 

[Billy Bob Bob]

yes,it has a flap that opens when water flows trough it should solve your problem if you can fit it to the shower waste

 

[Jimmeh]

once again gas man, you are a true LEGEND

 

[TGor]

Obviously it's badly installed and likely not to regs of any sort .. my advice .. do it properly or leave it alone .. once you touch it it's Yours!!!!!