Bath plughole ejecting bits of debris (but only once) - possible cause?

[Rollerball]

Usual bathroom arrangement - sink, bath and toilet.

When using the sink I sometimes hear glugging/gurgling from the plughole in the bath, this is normal.

Today I filled the sink with water to wash something (I very rarely fill the sink (maybe once every few months, if that)), usually I only briefly run the taps to wash hands, etc. Heard a lot of glugging from the bath plughole when I pulled out the sink's plug but didn't take any notice.

Later I happened to notice a moderate amount of small bits of blackish grey debris near the bath's plughole.

Tried to reproduce this a few times but it's not happened since.

So I partly filled the bath and refilled the sink to check the drains (I have a septic tank) and the water is flowing freely and the septic tank looks fine inside, water is flowing into it without any issues.

The debris in the bath didn't smell of anything, I think it's the type that you see accumulating just inside the overflow in the sink or bath for example.

So I'm puzzled.

Note that this has only happened once and I can't reproduce it (only hear a bit of the normal glugging at times).

Any ideas please as to a cause of the above?

Maybe an air pocket and the sudden dump of water from the sink shifted that air and ejected some bits of debris that was perhaps clinging to the bath's drain just inside the plughole?

I assume that my bath has a shallow trap as it sits very low to the ground (can't see the legs though as it has side panels).

Oh yes, and the full sink had in it a lot of foam/froth/bubbles because what I have been washing required a reasonable quantity of Fairy Liquid. This may be relevant.

I'm thinking of putting some Mr Muscle down the bath and sink's plugholes as I assume that there is debris accumulating in their white plastic drain pipes.

 

[Madrab]

It'll be a bit of backflow from the higher up basin forcing air back up the bath waste (on the same waste pipe I guess?) and blowing out the water seal in the trap a little. It'll be some of the soap residue that coats most traps. If you pull the bath trap you'll probably find some of that coating the inside of the trap.

Most people don't service/clean their traps until the block up, ideally the should really be cleaned once a year.

 

[Rollerball]

Thanks for the reply Rob.

Yes, same waste pipe for the sink and bath.

Getting to the trap to pull it will be difficult due to the way that the bath's main side panel is attached - is there a way to clean out any any soap residue, etc without removing the trap?

Mr Muscle gel for example?

 

[Mike13]

Buy some caustic soda granules, treat it with respect.
Only ever add it slowly, it gives off a LOT of heat when it dissolves, enough to melt a plastic fitting if you add too much to quickly.
But it will soften and move the sludge in the lines

 

[Rollerball]

Thanks. Out of interest, is that even more powerful than Mr Muscle gel?

 

[Madrab]

Best solution I can suggest is boiling water and any good detergent. A few black flakes isn't that much of a concern as that will always happen. If I can suggest anything, if you can avoid anything caustic/acidic unless you have a real blockage/restriction to shift. Given the pipework is hidden it can never be checked whether chemicals have caused any real damage and it can end up doing more harm than good. I've seen some real problems created by powerful chemicals damaging pipework

Once a month, boil a large pot of water and flush that down the waste with some detergent, same with every other trap in a households waste system, that will go a long way to keep everything clean and free from blockages/smells.

The ultimate is a properly design, self cleaning waste system and where possible everything run on it's own waste run to the stack

 

[Rollerball]

Thank you Rob, good point about chemicals possibly damaging pipework, that particularly being a problem if it's hidden.

 

[Harry Bloomfield]

Best solution I can suggest is boiling water and any good detergent. A few black flakes isn't that much of a concern as that will always happen. If I can suggest anything, if you can avoid anything caustic/acidic unless you have a real blockage/restriction to shift. Given the pipework is hidden it can never be checked whether chemicals have caused any real damage and it can end up doing more harm than good. I've seen some real problems created by powerful chemicals damaging pipework

Occasionally, I disconnect my kitchen drain, from where it goes into the gulley, block the pipe end up - then add some bleach to the sinks and back fill with water. Left over-night to soak. Next morning, drain, reconnect, and rinse. Entire system clean as a whistle.