Expected water loss from hot water system

Well, when my hot water system goes into a heating cycle, it emits a significant amount of steam. I am wondering if the amount of steam would equal around 20ml.

I just can't see where else I would be losing water. I know 20ml in 10 hours is stuff all...much less than a very slow leakign tap....but it is still 20ml that is unaccounted for.

Originally Posted by juan

These meters must be accurate.

They seem to be. The meters in Melbourne read to 0.01 litre but I don't know exactly how accurate they are.

I have read the meter one night and checked it again in the morning (while using no water overnight) - it hadn't budged (less than 10ml). I have filled a 10 litre bucket to check the meter, and it seems to read surprising accurately - well, as accurate as you can expect using plastic buckets for measuring!

I've got no idea why the water supplier would measure down to 10ml when they bill by the kilolitre

Originally Posted by chrisp

I've got no idea why the water supplier would measure down to 10ml when they bill by the kilolitre

Important to check for water leaks. Also it has to measure (tick over) in small increments anyway (its a small meter) so why not show a counter for it.

I will track down my missing 20ml I will run another test overnight and see if it is a consistant 20ml per 10 hours.

Originally Posted by wonderplumb

I agree its worth investigating, Im curious as to what type of heater you have that makes steam when heating...

It's one of those AquaMax units that I've seen selling at Bunnings. Seems to have a good energy rating. The manual says it is normal for the unit to emit steam during a heating cycle. On a cold night you would think something is on fire.

Gooner, the steam you are seeing is from the water vapour in the air. When the burner fires, it needs air to provide the oxygen for combustion, It will exhaust the combustion byproducts from the gas, plus the non oxidising components in the air, water vapour heated to steam and condensing on exposure to cool exterior air (the cloud you see) plus the nitrogen etc in the mix that we call air, from memory about 70% nitrogen, 20% oxygen, balance other gasses.

Originally Posted by Gooner

Over a 12 hour period I lost around 20ml water. It's not a major water leak, but not a good thing if it is, say, going into the wall.

Lets put things in perspective.

A schooner of beer is 425 millilitres, so 20 ml is not even a decent sip.

Also, where can one get a flowmeter that can accurately measure to that degree of accuracy. I think the scientific term is "not statistically significant".

Cheers

Graeme

Originally Posted by GraemeCook

A schooner of beer is 425 millilitres, so 20 ml is not even a decent sip.

I hear ya.... but again, my only concern was that even a small 20ml leak over 10 hours is just under 50ml per day. Big deal... but even 50ml a day leak within a wall can cause damage over an extended period of time.

Did you check the barometer at each reading?

Maybe the barometric pressure fell, allowing the various pipes and seals in your water system to expand ever so slightly, and take on the extra 20ml.

On the other hand, maybe a butterfly flapped it's wings in a remote Brazilian jungle...

If you are concerned about water leaks in your walls, go check them out, but worrying about a 2ml/hr loss over the whole plumbing system is a little bit obsessive...

woodbe.

I'm not sure how much the temperatuce fluctuates with the gas water heaters, but with electric there is a heat, cool and heat again cycle of a few degrees even with no water use.

When heating there will be some water discharged from the relief valve. That will keep happening every heating cycle even if no hot water is used. When the tank cools and internal pressure drops, a small amount of cold water will enter from the mains. Simple expansion and contraction here and nothing magic.

I don't know the figures but 20mL doesn't seem at all excessive to me. If I had one of those water meters then I'd check mine but I would have guessed it would be higher than that. I suspect the gas heaters may fluctuate less (?) which would reduce the water loss through expansion and contraction.

Originally Posted by Smurf

I'm not sure how much the temperatuce fluctuates with the gas water heaters, but with electric there is a heat, cool and heat again cycle of a few degrees even with no water use.

When heating there will be some water discharged from the relief valve. That will keep happening every heating cycle even if no hot water is used. When the tank cools and internal pressure drops, a small amount of cold water will enter from the mains. Simple expansion and contraction here and nothing magic.

Thats exactly what I think it is. 20ml seems about right. Probably more to do with the expansion/contraction of the water cylinder is it cools down thus allowing a little more water to trickle through. I had a shower about 30 minutes before I read the meter. So by the time I read the meter, I assume the HWS was fresh from a heating cycle.

In fact, I calculated that the water cylinder diameter would have to increase by a fraction of a mm (around 40 micron) to accommodate an extra 20ml. It would bulge in the middle meaning that it would probably be about 120 micron in the middle...about a growth of the thickness of a hair in radius....

Hmmm.. maybe I spend too much time thinking of this kinda stuff...?

Originally Posted by Gooner

T I had a shower about 30 minutes before I read the meter.

You need a hobby, try woodwork..

A single revolution of a water meter is usually 1 litre. x.001 stamped on the meter dial means one thousandth of a cubic metre (1 kilolitre)

When you heat cold water it expands. The colder it is (in Melbourne), the more it expands. This is what the cold expansion valve on the cold water inlet is for. The manufacturers instructions advise that sometimes as much as a bucket of water a day may be lost through the expansion valve. This is normal. Save it to a bucket and water your plants with it