slimy water in toilet cistern

[vivienz]

I havevwall hung loos with concealed cisterns, 3 in total one still awaiting the correct size of geberit flush plate. In the open cistern one I've noticed that the water is slimy and think that it's present in the others as well, evidenced by black mould forming just below the rim inside the bowl.

I've never had this problem before, not that I've noticed, anyway. As we have a sewage treatment plant, I'm reluctant to put anything too aggressive into the system but I'm also puzzled why it forming, seemingly in the closed cisterns as well.

Any suggestions?

[Jeremy Harris]

We have exactly the same issue, on all three loos, all get a black line around the water level, plus a bit of black staining towards the rear face.  I assumed it was because of our borehole water, or perhaps something to do with the softener, as I've never seen this before, either.

 

I've been reluctant to use bleach, because of the treatment plant, but have discovered that a small amount of dilute bleach is apparently safe to use, so I now keep a spray bottle filled with a bit of diluted bleach to deal with it.

[vivienz]

Thanks Jeremy, good to know I'm not the only one. I shall do the same.

[Jeremy Harris]

It will be interesting to find out if anyone else has the same problem, if only to narrow down the cause. 

 

In our case, I first thought it was because I'd tested the plumbing before we sorted out the borehole problems, so wondered if some contaminated water had got trapped inside the cisterns, so I flushed the whole house through with a lot of chlorine shock (which wasn't drained to the treatment plant) in the hope that it would be cured.  I've had our water tested (twice) so know there's nothing in it that could cause this, so I've been wondering if it may be related to the water softener.  Do you have a softener, by any chance?

[vivienz]

Yes, a Harvey.  Our water is mains supplied, so that could rule out your borehole as a suspect.

[vivienz]

Thinking further on it, I've never had softened water before.  I grew up in a soft water area, but softened water is different.  Both OH and I commented early on after moving in that the water from the shower had a slippery feel to it, which, I guess, is a diluted version of the slime accumulating in the cisterns.

[Jeremy Harris]

4 minutes ago, vivienz said:

Yes, a Harvey.  Our water is mains supplied, so that could rule out your borehole as a suspect.

 

 

We have a Harvey softener too, and similarly the water does feel a lot more slippery.  At least we've found one possible common factor, just need to know whether anyone else with a softener see the same black mould forming in their loos.

[vivienz]

I've had quick scan through a search on this and most explanations put it down to needing less soap in the shower.  This doesn't ring true, though, as I don't put soap into the loo cisterns.

[Jeremy Harris]

We've found that we've had to adapt to using a lot less soap and shampoo, just a fraction of the amount we used to use.  It's quite surprising just how little you need with softened water.

 

I can't work out why this should affect the loos like this, though.  We have found that it takes a couple of weeks or so for the line of black mould to appear, so a weekly squirt of diluted bleach and a quick wipe keeps it under control.

[vivienz]

The loo in our main bathroom doesn't get used that often as we have 2 others.  I think, as precautionary measure, I shall make a point of using that one a couple of times a week in case it gets to gunked up.

[Triassic]

It’s algal growth due to the water in the cistern being cold and the air above it being warmer.

[Onoff]

My concealed Geberit is on the mains. I shall have a look now.

[Gone West]

1 hour ago, Jeremy Harris said:

We have a Harvey softener too, and similarly the water does feel a lot more slippery.  At least we've found one possible common factor, just need to know whether anyone else with a softener see the same black mould forming in their loos.

I thought that soft water always feels 'slippery'. I notice the difference when we visit relatives in Orpington where the water is hard. We have a Harveys water softener but use hard water for the toilets and don't have a problem with mould. Our concealed cisterns are insulated if that makes any difference.

Edited November 29, 2019 by PeterStarck

[scottishjohn]

I have always lived in soft water areas and i notice the opposite if I go to hard water area -

could it be the softner is OVER softening the water?

are they adjustable 

[Onoff]

8 minutes ago, PeterStarck said:

I thought that soft water always feels 'slippery'. I notice the difference when we visit relatives in Orpington where the water is hard. We have a Harveys water softener but use hard water for the toilets and don't have a problem with mould. Our concealed cisterns are insulated if that makes any difference.

 

The Geberit cisterns are insulated I think. Mine certainly is.

Edited November 29, 2019 by Onoff

[vivienz]

46 minutes ago, scottishjohn said:

I have always lived in soft water areas and i notice the opposite if I go to hard water area -

could it be the softner is OVER softening the water?

are they adjustable 

 

When the softener guy came out he did a water hardness test to check for this. The test result came out lower than I was expecting, so I don't think that we're over softening.

[Gone West]

I've just had a thought @vivienz you and Jeremy could try an experiment of leaving the lid up to see if it's a ventilation problem.

[Jeremy Harris]

16 minutes ago, vivienz said:

 

When the softener guy came out he did a water hardness test to check for this. The test result came out lower than I was expecting, so I don't think that we're over softening.

 

 

It's physically impossible to "over soften" water.  Once all the calcium ions have been exchanged for sodium ions nothing else is going to change.

[vivienz]

16 minutes ago, PeterStarck said:

I've just had a thought @vivienz you and Jeremy could try an experiment of leaving the lid up to see if it's a ventilation problem.

Leave the lid up?! Do I detect a man seeking a scientific reason not to put the loo seat down, Peter?????

[Gone West]

22 minutes ago, vivienz said:

Leave the lid up?! Do I detect a man seeking a scientific reason not to put the loo seat down, Peter?????

It really was Wendy's suggestion.    Lack of ventilation around the pan if the lid is a good fit?

[vivienz]

I don't think that can be the case. The downstairs loo doesnt have the flush plate fitted yet and so the water in the cistern is open to atmosphere, therefore well ventilated. The water in this cistern also has a lot of slime in it.

[mvincentd]

We have a Tapworks water softener, mains supplied water, moved in same time as you @vivienz , no mould so far.

[Cpd]

Never had this problem but my bathroom has never been heated and is often below 10 degrees At this time of year........  

[vivienz]

26 minutes ago, Cpd said:

Never had this problem but my bathroom has never been heated and is often below 10 degrees At this time of year........  

 

That's not a bathroom, it's a fridge! I've never seen mould on ice cubes!!!

[vivienz]

An update on this thread.

 

I made up a dilute solution of household bleach in a spray bottle today, as per Jeremy's example. I gave a little squib to clean all the toilet bowls but the most interesting effect was on the cistern without the flush plate. I gave a couple of sprays directly into the cistern and much of the snotty slime was gone in a matter of hours, so it seems an easy one to solve.