I've a wet bottom dripping on the floor

[woodenhead]

Attention grabbed.

 

Ok, my toilet sits on tiles above the pipe run between the boiler and the hot water tank.

 

This means that whenever we have the boiler on it creates condensation on the bottom of the toilet bowl (not the cistern) which then drips onto the tiles and collects in a pool that then runs out under the bottom of the toilet and gathers in a pool in front of it.

 

Clearly putting a source of heat right below cold water with an air gap is a clear oversight from when the house was built 18 years ago. We've always had issues with condensation on the cistern but put it down to it being on an outside wall but maybe it was really the pipe run causing the issue and now I can see it on the bottom of the toilet as well since the bathroom was renewed in the summer.

 

I can stop it coming out from under the toilet with sealant - but how can I stop the condensation forming in the first place underneath the toilet?

[simonhaynes72]

Make sure the pipework is properly lagged!

That should prevent your damp spots.

 

Make sure you seal the joins properly too.

Simon

[woodenhead]

It's not the pipe work, the three inches that is exposed is fine - I've had a mirror behind the toilet looking at the bottom of the bowl and it has water on it.

 

All I can think is that the modern exposed style of the toilet has exposed the U bend to the heat from below and susceptible to condensation.

 

One thought I've had is to fill the underneath with expanding foam to insulate but that might be drastic and then impossible to reverse if it doesn't work.

[Baby Deltic]

Painting the inside of the cistern with a suitable paint will help prevent condensation on the outside. As far as the pan goes, If you can see under it, you might want to coat the underside in a suitable insulating material (providing it is inconspicuous).

[Baby Deltic]

P.S., when I read the title of the thread, I thought you'd had a 'knock on'. (fart and lose the gamble)

[woodenhead]

Cheers Baby Deltic, have to lie on the floor with a mirror against the wall and a torch placed under the toilet to see what was going on so I think it is inconspicuous.

 

Do you know what this insulating paint is called so I can look it up?

[Black Sheep]

are you certain that there's not a leaky joint somewhere between cistern and pan?

[jcm@gwr]

Firstly, I agree with lagging the pipework, by any means you can.

Secondly, one of the main reasons for condensation is lack

of ventilation or decent airflow. Do you have an extractor

fan in the room or does the window open?

I would explore these options before trying to paint the pan.

Jeff

[plumber/bathroom fitter if your interested]

[woodenhead]

I had a good feel around it when I was looking and the joints seem fine and dry and it's definitely clean water I am seeing and if there was a leak it would have had a definite line whereas the damp is all over the bottom of the bowl.

 

That insulating paint seems to be coming back as snake oil on Google.

[chris p bacon]

This is a first, never heard of condensation forming on the bottom of a toilet bowl because of pipes below in a floor void.

 

What I do know is that if your toilet is in a bathroom and you don't vent the room when bathing/showering one of the first places steam/vapour will condense is the base of a cistern making it look like the cistern/pan is leaking. As the cistern is filled regularly with cold water it is the coldest item in the room.

 

Is your wc in a bathroom with ventilation?

[Baby Deltic]

I found this little excerpt:

 

Problem: Tank sweats (has condensation on the outside)

Solution:

If your tank is producing a lot of condensation you might want to insulate your tank. Turn off the water to your toilet and flush it many times until all the water is gone. Soak up any leftover water with towels. Let the inside of the tank dry. Get some watertight glue and attach a 1/2 of foam rubber to the inside walls of the tank. Let dry before refilling.

[woodenhead]

The bathroom is well ventilated and there isn't condensation elsewhere - a bit on the Cistern as you would expect and then this pool underneath - at first I assumed perhaps it was running down from the Cistern and trapping around the base. It was only after I looked underneath I realised it was the actual bowl that was the issue.

 

If I fill the space with expanding foam it would remove the air and create an insulation barrier between the heat of the pipes and the cold water in the bowl but it seems drastic albeit invisible.

 

Edit: putting in foam might also make it messy to access if there was an issue with joints later as well.

[woodenhead]

It's under guarantee, I think the best bet is to get the bathroom fitters back out - it's from Wickes and let them suggest something.

 

I will also take another look in the morning at the rubber seal around the toilet soil pipe connection and that there are definitely no hairline cracks anywhere.

[chris p bacon]

The bathroom is well ventilated and there isn't condensation elsewhere - a bit on the Cistern as you would expect and then this pool underneath - at first I assumed perhaps it was running down from the Cistern and trapping around the base. It was only after I looked underneath I realised it was the actual bowl that was the issue.

 

If I fill the space with expanding foam it would remove the air and create an insulation barrier between the heat of the pipes and the cold water in the bowl but it seems drastic albeit invisible.

 

Then you have a leak somewhere. it is not unknown to have a crack in the china that you cannot see, you could try putting some blue food colouring in the cistern water overnight and some red in the pan and see whether it is a leak from either.

 

I wouldn't use expanding foam under the bowl...........it's unbelievable what power to shift that stuff has !

[34theletterbetweenB&D]

You may just have to live with it. We replaced an original wc in our house in a refit some years ago with a compact Armitage Shanks suite. Both cistern and bowl were noticeably much lighter than the porcelain they were replacing. In winter when the cold water feed is truly cold there is light condensation on the cistern exterior corresponding exactly to the water content. On the bowl, there is occasionally a little condensation at the foot corresponding to where the trapped water is inside. As it happens the other identical 'original' wc in the house was not replaced, lives in the same temperature regime, and if anything in a room with less ventilation: never any condensation on it. So I am pretty confident of the root cause here.

 

Quite simply the much thinner wall of the new suite means a greater heat flux, and thus the condensation. (Something of a return to the past, I am sure I will not be the only one who remembers the gentle rain from above originating from high level mounted cast iron cisterns?) While the idea of internally insulating the cistern to reduce the heat flux appeals, it is already a minimum volume job, and barely has enough water in it to cope with the bigger jobs it has to deal with; let alone the fact that the siphon and much of the mechanism are hard up against the sides in various places. So, coping strategy. When the outside temperature leads to regular ground frosts, I can expect the cold water supply temperature to fall below 3C, and that is when the condensation forms in sufficient quantity to run down the cistern walls and drip. An arrangement of two freezer trays to catch the drips is deployed for the duration of such spells of cold weather.

[Guest stuartp]

You may just have to live with it ... An arrangement of two freezer trays to catch the drips is deployed for the duration of such spells of cold weather.

 

Same here, although ours is a rather less elegant margerine tub and one of those absorbant sausage-dog things intended for windowsills. No condensation on the bowl though, just the cistern. I did wonder whether insulating the outside of the cistern would work (in the same way that 2mm polystyrene under the wallpaper works on outside walls - keep the damp air away from the cold thing instead of stopping the cold thing getting cold) - it would be much easier to knock up some sort of cistern cosy than to insulate the inside of it.

[woodenhead]

I did think of drip trays - but I cannot get anything in there as it is very close fitting to the wall, just enough space to have a look see with a mirror - no way I would get something filled with water out.

 

Perhaps a drip tray and I could siphon it off the old way with a rubber tube and a quick suck - on second thoughts it is a toilet and what if it is a crack!

[PhilJ W]

Quite simply the much thinner wall of the new suite means a greater heat flux, and thus the condensation. (Something of a return to the past, I am sure I will not be the only one who remembers the gentle rain from above originating from high level mounted cast iron cisterns?)

That brings back half forgotten memories, a dollop of freezing water landing on one's bare cheek(s) just as you made yourself comfortable.

[woodenhead]

It was the spiders living behind the high level cistern I worried about.

[AndyB]

My neighbour took up diy to earn a living as an odd-job man.

His first client asked him to fit a new bathroom suite.

After a week or so the client reported something strange.

Every time she flushed the toilet the combie boiler would burst into life.

You guessed it.

So he went back and connected the cold water supply to the toilet cistern.

I should have mentioned that the job he had before handyman was as a banker in the city.

You could probably have guessed that too.

[34theletterbetweenB&D]

... I did wonder whether insulating the outside of the cistern would work (in the same way that 2mm polystyrene under the wallpaper works on outside walls - keep the damp air away from the cold thing instead of stopping the cold thing getting cold) - it would be much easier to knock up some sort of cistern cosy than to insulate the inside of it.

It certainly does. I experimented with a patch of some of SWMBO's cold frame insulation which is a tough spongy translucent sheet about 2mm thick and it did the job. However, SWMBO did not approve the resulting appearance (the suite is all slinky and curvaceous, and covering it with a cistern cosy was not at all what she had in mind).

 

But I have an idea. The front of the cistern the condensation isn't a problem, because it runs down onto the rear of the bowl rim , and thus down into the bowl. So what I have in mind is to look for something that can be used to form guttering stuck on the cistern sides very near the bottom with a 1 in 10 fall, directing the condensation to the rear rim of the bowl. (The back face and base of the cistern is three times the wall thickness, no condensation there.) Just have to remember to look for something to the purpose in every hardware type store I happen to enter...