adding hot water to a toilet cistern?

[carlos21]

the toilet cistern is badly condensated due to the cold water feed being very cold this time of year, so I am going to T into the hot water pipe and put in a valve to adjust the amount of hot water plus a couple of one way valves to stop cross flow, or a thermostatic mixer valve, 

anyone done this or have any thoughts?

thanks carl

[Nickfromwales]

It’s been discussed recently, so can be done with a cheap TMV. Just set it as low as you can but also plumb it in with an isolator on the hot side, so hot can be shut off for the rest of the year. 
 

The TMV will allow cold through without hot pressure present, but it won’t let hot through without cold pressure; these are set up to prevent scalding if the cold fails. 

[ProDave]

A typical cistern is about 6 litres.  It would have to be very close to the HW tank otherwise the hot water won't have even got there before it is full.

[carlos21]

17 minutes ago, ProDave said:

A typical cistern is about 6 litres.  It would have to be very close to the HW tank otherwise the hot water won't have even got there before it is full.

yes i thought that could be the case, but i figured the not so hot water in the pipe would still be a lot warmer the the cold feed from the header tank.

[carlos21]

22 minutes ago, Nickfromwales said:

It’s been discussed recently, so can be done with a cheap TMV. Just set it as low as you can but also plumb it in with an isolator on the hot side, so hot can be shut off for the rest of the year. 
 

The TMV will allow cold through without hot pressure present, but it won’t let hot through without cold pressure; these are set up to prevent scalding if the cold fails. 

good point to put in a valve in hot feed, the only thing that concerns me slightly with the thermo valves is they seem to only go down to 30 degrees in temp which is way hotter than i need it, although the condensation is so annoying id nearly hook it straight up to the hot feed.

 

[Nickfromwales]

30 is cooler than skin temp, so you'll not suffer too much annoyance.

[JohnMo]

I would expect seals within the system to complain and not last long with hot water. But @ProDave say 6 lt isn't much draw off from your cylinder - if it's a combi no hope, you'll just use gas and still fill with cold water.

[saveasteading]

18 hours ago, carlos21 said:

the cold water feed being very cold this time of year,

Could you adjust the insulation.

 

Why is it so cold? Mains water is at ground temperature.

Perhaps introduce some reduced insulation somewhere along the cold line, so that it warms on the way?

[Iceverge]

I suspect your humiliation is extra high in the bathroom. 

 

Is the extractor fan working? 

 

 

[Mr Punter]

12 minutes ago, Iceverge said:

I suspect your humiliation is extra high in the bathroom. 

Only if he gets caught naked.

[saveasteading]

Add a humidity sensor for the fan and a humility sensor for the fan, door and window blind.

[Nickfromwales]

Has everyone lost the grasp of plain English here lately? 
 

National typo week here atm lol. 

[ProDave]

58 minutes ago, saveasteading said:

Why is it so cold? Mains water is at ground temperature.

Our water comes from a mountain loch about 600ft above sea level, at this time of year fed by snow melt probably.  We often joke why is it not coming out of the taps in lumps.

 

We only get condensation on the cistern in the utility room when some washing is on the airer, temporarily pushing up the local humidity (spell checked)

[JohnMo]

19 hours ago, carlos21 said:

the toilet cistern is badly condensated due to the cold water feed being very cold this time of year

I would actually step back and ask why?

 

Does your room have adequate ventilation?

 

Above 60% Humidity: In a typical room (20°C), the dew point is approximately 12°C. Since your water is much colder (6°C), heavy condensation is guaranteed.

 

At 50% Humidity: In the same 20°C room, the dew point drops to roughly 9°C. While lower, it is still above 6°C, meaning condensation will likely still form, but at a slower rate.

 

Below 40% Humidity: To completely stop condensation on a 6°C pipe in a 20°C room, you would typically need to lower the humidity to below 40% (where the dew point is roughly 6°C or less)

 

So I would be looking to fix your ventilation, not faffing about with hot water - then your issue will disappear. And you will have a healthy indoor environment as well.

[stu w]

I line them, cures the problem, very little loss in capacity and no more condensation 

[sgt_woulds]

What material did you use for this?  How the metalised finish holding up?