We recently had our down stairs loo refitted, wash hand basin and loo. The room is about 3' by 4' has a single panel radiator 1' square-ish which is fitted with a thermstatic valve, also a double glazed upvc window.
Since the refit there ssems to be considerable condensation on the cistern, previously no problems with old set up.
The only way round this is to leave the window on the vent setting, but whats the point in heating the room in the first place, if this is done no problem with condensation but no one wants to use the loo at night because its to cold!
The analogy I can think of is a beer glass in the warm pub syndrome, any ideas
… the condensation not the beer

Cheers

What's in there producing water vapour?

Is the cistern filled from the mains or a tank?

Is the new cistern different material to the old one?

was it re-plastered?

if it was then the walls could be sweating a bit for months and in such a small unventilated space you will get condensation on anythign below ambient temparature.

Line the inside of the cistern with polystyrene tiles, should prevent the condensation build up on the cistern.

The trouble is that the water inlet to the house is about 2' away, the first T is on the feed pipe is to the wash hand basin and cistern. I wondered if its down to just the temp' of the incoming water, winter and all, but it didnt happen on the old cistern.
Could be the different ceramics in the cistern?

Mine does the exactly the same. Cold water filled straight from the mains. Warm bathroom, cold cistern = lots of condensation, in fact a surprising amount, enough to leave the floor wet where it runs down. Dont know the answer other than hoping summer comes soon. I've thought about trying to line it with some kind of insulation as mentioned above, but Im not sure what and how or even how sucsesfull it would be?

Looks like leaving the radiator on the freeze setting and the window on vent.

On the subject of venting have had a guy round to look at cavity wall insulation, however because we have an open fire he would have to fit a 5" vent in the lounge. It would be like sitting in howelling gale, anyone else had this problem?

Don't you already have a 5" vent…it's called the chimney? 🙁

Smartay
Yes. Brand new house, no chimneys and we wanted a gas fire. They cut a 5" vent in the louge wall "..cos it's law, mate…"Now we can hear road noise and wind all the time???

The only way round this is to leave the window on the vent setting

you need to ventilate the room somehow – open the window – or another window and keave the bathrrom door open.

always amazed at people who seal up their bedrooms (windows & doors shut) than complain about condensation!

It's all down to temp differences. You've got incoming water temp of say 4 degrees and an internal temp of 18 degrees. That's 17 degrees difference. Your analogy of the cold drink on a hot day is a good one. You can't beat the physics. You can twist them though.

I assume the new cistern is a dual flush low capacity item so don't line it with polystyrene insulation because it won't have enough water to flush properly. It's also probably thinner ceramic than the old one so it affected quicker by temp changes.

Set the radiator to 1 or 2 on the TRV. To be fair there's no reason to have a rad in there seeing as it's such a small room. It will be cooler than the rest of the house but then it will also reduce the temp difference.

Close the door.

Don't have the handtowel(s) drying on the rad.

Now a final option would be to swap out the extractor fan for a heat recovery one. A wall mounted one will be £300 odd though but it will keep the water vapour levels in check.

you not got a trickle vent?

Wouldn't help. It's the temp difference that's the problem not the amount of water vapour.

OK then, so its going to be rather chilly in the loo that'll please everyone!! to be honest since I've opened the vent and reduced the TRv setting the condensation has gone.

On the cavity wall episode when I had the double glazing fitted I had all the windows fitted with the ability to open them, yes being raised on open fires etc I realised you needed some form of draught for the fire to burnt.

So in our lounge there are three windows but that still isnt enough for present legislation. Apparently the next owner maynot be that clued up on how combustion works!!