Kitchen Sink Drainage issues

[Tel77]

I seem to be getting frequent airlocks (I suspect) in the kitchen sink waste pipes and can't get to the bottom of it.
Once I clear the airlock by slackening of the trap and venting it then it runs freely for a couple of days but then happens again and starts backing up the sink when either the dishwasher or washing machine are on.

I've had all the pipework off and made sure it's clear which it is (all the pipework above the ground that's accessible anyway) but can't figure out why it all works as it should for a day or two and then starts all over again.

Does anyone have any ideas of what I can do or try?

 

[HERTS P&D]

Check the outside gully/manhole.

Andy

 

[Hugh Jaleak]

Sounds to me like its partially blocked. Cleaning out some of the pipework wont solve anything if the problem is in the other section!

If you've put any chemicals down there be extremely careful if you dismantle the pipework, those chemicals are lethal!

 

[Tel77]

Thanks for the replies.
I'll lift the manhole when the weather clears a bit and have a look.

Would that not cause it to back up all the time as I seem to be able to sort it for a couple of days and then have to vent it all again.

I've had all the pipework off that's above ground and cleared it all out so really hoping it's not an issue underground.

Any recommendations on chemicals that may break down anything that's blocking it?

 

[bathjobby]

Sounds like you may have already answered your own question;

I seem to be able to sort it for a couple of days and then have to vent it all again.

i.e. a venting problem rather than a blockage in the drain pipe.

 

[Nige F]

I've had all the pipework off that's above ground and cleared it all out so really hoping it's not an issue underground.

?

It will be - despite hope springing eternal Herts Hugh and me , we all agree

 

[Tel77]

So is this looking like I'll have to get someone in to clear it from outside the house?

 

[Hugh Jaleak]

Do you know where it goes once it disappears? Into a gulley or direct connection to stack or drain?

 

[Tel77]

I'm not sure where it goes if I'm honest as it disappears under a concrete floor so not sure how I can find out

 

[Hugh Jaleak]

If there's not a gulley adjacent to the wall outside in that vicinity then I imagine it's a direct connection to the drain. Need to lift manhole covers, whilst running some water down the sink and see where it emerges. This should identify the line the sink uses.

If you cant see any water appear then further investigation may be required, there could be a blockage in the drain (which could account for the problem) or the builder was put to confuse everyone with the drainage layout.....

 

[Tel77]

I think there's a manhole cover at the front of the house along with a drain at the side(end of terrace) so I'll take a look when the weather clears