To not want my house to be heated with bath water?

[Iburntthecakes]

Please settle this for me and DP.

After a conversation with colleagues DP has decided that it is a waste of money draining all that hot bath water down the drain. Instead if we leave it in the bath then the heat and the steam will circulate through the house thereby reducing our heating bill

I've just had to deal with cold grey bath water two days running

Please help him see sense.

OP, just put a thermometer in the bathroom and check the temperature before and after the bath is run and every hour after. Please report back on how much difference the bath water makes to the room temperature.

My prediction is: bugger all.

Hmm, the fridge thing is I believe to do with energy going into a room so therefore the temperature must go up. However, the wasted food would be a very real issue
I'm not the best at keeping a tidy home but leaving the water in the bath is a bit too grim even for me. I also needed to bath 6 month old. However she can miss her bath tomorrow if the same thing happens and I will indeed leave DP to it.

Thanks all - I'm hoping this thread might shame him enough to abandon the plan.

What you need is to drain the hot water to let it heat water you need for the rest of the house: www.engadget.com/2009/03/26/ecodrain-heat-exchanger-makes-good-use-of-warm-waste-water/

Yes. A waste water heat exchanger. Your DH is just wasting all that hot water by not draining it and capturing the heat.

He's right about the fridge. The fridge effectively removes the heat from the food and radiates it back into the room, so by leaving the door open you'd make the room hotter.

Bath water is only going to transfer heat for a few minutes while it's hotter than the ambient room temperature. The problem is that the water will cool by evaporation, carrying highest-energy molecules into the air - water is then likely to condense on coldest surfaces, transferring energy to outside walls / windows. Given that there is some heat transfer to the outside, it may even be that your heating system has to work harder to maintain the same temperature in a greater mass I.e. bathroom plus water.

It would be more energy efficient to have a colder bath, because it requires a relatively large amount of energy to heat water.

In the absence of a proper heat exchanger system, it might work if he were to pour the bath water into enclosed receptacles (black probably best to radiate heat) and then place the receptacles in each room until their temperature falls to room temp.

However this would not meet his objective of justifying being a lazy arse and leaving you to clean the bath.

Stop him watching Spongebob.

I think I see what you mean Inertia. Will see what he says to that in the morning. Off to bed now. Thanks!

The most efficient way of heating your DP is to get him one of these.
www.argos.co.uk/static/Product/partNumber/4500881.htm