discobay

I like the idea of instantaneous hot water whenever I want but I am finding some properties that use gas storage, in particular Rheem branded, units. I have used electric storage and though have never run out of hot water I was always concerned that this could happen if say everyone had a bath or guests were staying.

Can I find out from anyone here the merits of gas instantaneous hot water over gas storage?

MartinLuther

I'd go instantaneous if you can. The main problem with it is that you need a bigger gas pipe and/or higher pressure than for storage. So it's not always possible or economic (due to the installation of a bigger pipe).

Have you thought about gas backed solar? You don't always need a bigger pipe for that as generally it's boosting up the water already heated by the sun. Check to see if you can get a rebate where you live as it makes these more affordable. Solar tubes are another alternative for water heating but I don't know much about them yet.

discobay

Actually I should have said that I am looking at renting for now so all modifications are out. A place I saw last week was built 12 months ago and has gas storage. As it is so new I thought that mabe this kind of hot water system is becoming de facto.

mecheng

Check what the other properties around it have. If they are the same, just ask the neighbours if they have had any issues.

EvannTel

I've had both and reckon instantaneous is the way to go, cheap and plenty of hot water.
If you;re going rental, get the best rental irrespective of the water system - you'll learn to live with it if not perfect. Nt sure many consider the HWS when choosing a rental.

discobay

You make a valid point. However I do like my hot water to be under my control and having come from a home with electric storage heated during off-peak hours I would hope to improve my quality of life with something better. But hey it is only a rental and the place I'm looking at is near new so as you say choose the place based on more important factors.

leave_n_on_a_Jet

all depends on how much hot water you use.

about the best option is to use 2 cylinders, heated by some form of solar.
when the weather is hot no probs all hot water via solar, in cold weather instantaneous (boosted) will give you never ending hot water (as long as everything is working, as with any system) but it will use more gas, stored hot water via gas will use less gas per same volume of hot water, down side of stored hot water is if you dont use it all you are paying to heat water your not using, it takes longer to heat the water, (there are fast recovery systems avaliable) a lot of gas stored water systems will heat the top 1/3 of the cylinder only.

So in short its something to talk about with your installer.
(i know your renting etc, the above is in general for anyone thinging of an installation)

James

discobay

Yes that sounds like an ideal system though I have heard a lot of good things about heat pump systems too.

The unit I have seen at the rental is a Rheem. It is tall, slim and very modern looking. Maybe the real eastate agents can find out more for me.

Wol

We installed a Rinnai 32 instantaneous and it works beautifully - you never run out of hot water of course.

Always seem comical how Australian houses have their hot water cylinders outside exposed to the weather - airflow past it is the easiest way to lose heat continuously!

leave_n_on_a_Jet

Heat loss is not a major problem due to heavy insulation etc, the main reason to have these installed outside is if they are not maintained they can explode.

If they explode outside there is not usually much damage where as if it is inside you can find you have a new skylight & a new open plan area where the cylinder was.

http://www.youtube.com/watch?v=ekEHfihiNz4

James

Wol

I would have thought a tank was filled with water, in which case it couldn't have any stored energy and might split but not explode?

American houses have their cylinders in the garage - I have never heard of one "exploding".

My neighbour's tank in opposite our boundary and to see it standing there, filled with (presumably) hot water in a 70Kph gale at a few degrees above zero (common during August/September) while reading all the guff about saving energy makes me laugh <g>.

What_a_life

the hot water cylinders are mains pressure, unvented, there is a check valve (only allows water to travel in 1 direction eg forward) as water gets hotter it expands, so these type cylinders are fitted with a pressure relief valve to release the pressure if it gets to high, plus over heat stats etc, if these fail the pressure builds up in the cylinder, with-in these cylinders is a expansion vessel which normally takes up the expansion of the hot water, water normally boils at just under 100 degrees, however if you increase the pressure (as in a pressure cooker) the water can be heated to above 100 degrees. So if we have a situation where the safety devices fail and the water is still heated, the pressure with in the cylinder will rise until the cylinder fails, when this happens, if the water with-in the cylinder is above 100 degrees as the pressure drops when the cylinder splits the water will instantly change state from water to Vapour (Steam) this is what causes the explosion. because steam requires about 1600 time more space than the water did, thus the cylinder explodes as it cannot contain the steam, Ka-Boom

you wont get much heat loss on a cylinder standing outside as they are heavily insulated, just thing of a Thermos flask, hot drink in winter will stay hot all day, and the only insulation it has is an air gap.

James