April 2010 - Pipe Insulation

Even the most efficient water heating systems still face the problem of water cooling in the pipes before it reaches the point of use. We collect about half a bucket of cold water in our shower before the hot gets there, and a substantial amount of cold water goes down the kitchen sink while waiting for it to warm up also. This month we decided to insulate the water pipes where we could get to them.

Initial Time: 15 minutes to cut and fit insulation piping on outside pipes. Tyson got into the roof space to see if the pipes were exposed there also, which was an additional time commitment, but after insulating a section of gas pipe by mistake he concluded that the hot water pipes are not in the roof cavity, so I won't count his roof crawling time here.


Initial Cost: We were given four metres of insulation piping free as a promotion from Environment House and bought some extra from Bunnings - $6.89 for a two metre section.


Ongoing time or cost commitment: zero.

Impact: We still run a lot of cold water in the shower before the hot kicks in, as it is on the other side of the house to the water heater. Its hard to say whether the temperature is warmer once it gets going, as we did this right on the change of season so the pipes are contesting with colder weather than before we made the change. In the kitchen, which is closer to the water heater, we have noticed that the water appears to have less cold delay, and is hotter when it arrives.  This is definitely true in the laundry, which is directly through the wall from the water heater.

I can't give a precise measure on any of that, though.

Update: Tyson has put some measurements in the comments. 

Also I think I should emphasise that even when you are not using any hot water, the outlet pipe from a storage hot water system acts as a kind of wick, drawing heat out of the storage tank. Insulating the pipes not only keeps the water we are using hotter, it also keeps the water waiting in the tank hotter.

February 2010 - Hot Water Temperature

Heating water is one of the biggest users of energy in a house. We have a large storage gas hot water system. This means that it works all day to keep the 135 litres inside hot and ready to use. This month's sustainable action was to reduce the temperature that the water is heated to and stored at. As I sit to write about how much effort it took and how much impact it has, I can't believe we didn't do it sooner. The water is still easily hot enough to have a great shower, even on a cold morning (not that we have had many of those in Perth this year).

Initial Cost: zero

Initial Time: five minutes

Ongoing time or cost commitment: zero

Impact: I thought there would be a nice easy calculation for this - an equation of 'water takes x units of energy to heat to y temperature therefore a reduction of z degrees means an xyz reduction in energy usage'. Tyson sighed at me and said its not as simple as that. Each brand of water heater uses a different amount of energy when new, and then it depends how old the system is, whether we use our hot water all in one go or in little bits through the day, where the system is located (if its in the sun, it stays warmer. Duh. Why didn't I think of that?), what the climate is like, and so on. Also when we opened the box we found the dial didn't say what actual temperature it was set to. It was on the highest one - at a guess probably about 70-80 degrees C. We turned it down from '5' to '3', which we guessed would be about 60 degrees C. (It's not safe to store hot water at less than 60 degrees C as there is a danger of legionellas breeding)

BUT: Our recent gas bill was about one third less than the same period last year, and we only use gas for cooking and hot water, so even without a clever formula I can say that it is making a big difference!