Foam backing up dishwasher waste...

[fizzput]

Been and cleaned 40mm waste pipe with snake and melt as foam from washing machine has been backing up dishwasher waste. Both pipes are about 50cm rising vertically from falling horizontal run, and about 10 cm apart.

One thing i have identified to the customer is once the common horizontal waste elbows out on the external wall, there is a distinct sag in the 3 m run too the drain pipe which when lifted as much as possible (kitchen sink waste tee's in about halfway along) run water held in it through to the drain so obvioulsy dodgy....

Prob is i've cut the waste in the 3m outside run and find no real obstruction and there's nothing upstream to the appliance connection, also this system (rubbish a sit is) has qorked fine for the 5 years the customer has lived in the property.

So i'm thinking perhaps the washing machine is showing it's age and not working as it used too so with dodgy plumbing has it's work cut out to clear the outflowing foam. water still goes ok, it's only the foam which i guess is backing up from the water plug created by the sag.

Any thoughts??

Thanks

Mark

(obviously changing the pipework is the ideal solution but this customer is a real stickler for detail...'pita' )

 

[Alanka]

It may just be that the 'sag' has slowly been worsening until it has reached the point when enough water/foam is trapped to cause sufficient back-pressure or airlock to be a problem.

Plastic pipework does gradually degrade/yield in sunshine and when particularly hot water is run through it, so that unsupported lengths can sag under their own weight. Seen it often.

Could be that gradual build-up of deposits in the pipe has added to the weight and the sag. (?)

 

[fizzput]

Thanks alanka,

i hadn't considered that as an option, just wondering if the sink waste conection would have prevented much movement in the sag, i'll pop round the customers house to see what play there may be.