Hot water cylinder replacement - outside cylinder? or gas?

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georgea

49 posts

Geek

#277024 22-Sep-2020 11:58

Our 30 year old 180L low pressure electric cylinder has sprung a leak and needs replacing, and we are trying to decide on what to replace it with.

We are a family of 5 with pre-teens - so lots of showers and baths, and we currently occasionally can run out of hot water... damn kids :)

Our house was built in 91, on mains water, but a small hot water cupboard that can only fit a 180L cylinder which is currently low pressure. But our pressure isn't too bad. Our tapware is newish and good quality.

Options:

1) replace with another 180L low pressure electric cylinder - no risks with piping and cheapist, but seems old school

2) replace with a 180L mains pressure electric cylinder - cheap, but worry we would go through the 180L even quicker with mains pressure

3) replace with an external heat pump system - after reading posts on here I'm not convinced this is a great option - longevity, noise, initial cost, and we live in Hawkes Bay so it can get cold and therefore be inefficient.

4) replace with gas infinity system - this seems the popular option, but we would have to be on LPG bottles (about $125 each) and general opinion seems very split over whether this is cost effective or not. Having to keep track of and order bottles sounds annoying if there isn't a decent cost benefit.

5) replace with a external 250L electric cylinder - could be connected to heat pump or solar in future.

I am leaning towards 5, as we get a bigger cylinder, we get cupboard space, and it could be used for other options in the future. We do live 300m from the coast, so I worry about corrosion, but I guess we could build something around it to protect it more. We also plan on being here another 2-5 years, so I need to think about what potential buyers would want.

Any opinions on the above? Has anyone else got an external electric cylinder? How do others find the cost of infinity systems on LPG bottle gas?

Zeon

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#2571940 22-Sep-2020 12:39

I got a Rinnai outdoor water cylinder. It's placed on a concrete pad between the main house and studio (about 10m of piping to get to the house). Currently its just electric but the plan is to put solar on the roof of the studio at some point. Apart from the element blowing just after 1 year (they replaced it for free) its been fine.

We have the 340L model to feed the house (6 bedrooms, 2x kitchens and 2x bathrooms) and studio (1x bathroom). Our pump is 180L per minute at full bore and the water moves out of that cylinder just fine - not that its a comfortable shower with the related pressure! I'm surprised the shower head doesn't explode. I do want to insulate the pipes, need to learn the correct way to do it.

Speedtest 2019-10-14

Blurtie

278 posts

Ultimate Geek

#2571963 22-Sep-2020 13:04

We've got an infinity system and we're pretty happy with it overall. We're a family of 4, 5yr and 9mth old, and I would say we're quite high users. Typically go thorough a bottle a month, although during winter we do seem to order more frequently for obvious reasons. I've seen on these forums of other households getting much longer out of a bottle - although I can't say what their usage patterns are.

You're right, it is annoying keeping track of the bottles, the other half definitely doesn't do it! But it's a pretty simple/painless process - I'm with Genesis, they have a handy app for reordering bottles. Once you're aware of your usage patterns you'll know when to check/order.

In general, I think we would look to get another infinity system if ours was to break.. Our in laws have a low pressure cylinder, and every time we stay with them it's horrible having showers there.. We can't wait to get back to ours to get 'clean' again..

pih

181 posts

Master Geek

#2571981 22-Sep-2020 13:20

Gas hot water is nice, unless you sometimes like a small dribble of hot water (say for shaving or rinsing dishes), then it cuts out and you're left with cold water.

Having said that, it's nice to have "unlimited" hot water when you need it (like when said pre-teens become teens). If I were you I'd just buy two bottles and get a switch over tap installed, then order a new bottle every time one goes empty. That way you're only ever out of hot water for a few minutes at most.

kotuku4

381 posts

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#2571983 22-Sep-2020 13:20

Is the limitation on height, width or both with 180 litre cylinder?

I replaced a 180l low pressure the taller 270l low pressure.

Heated via solar PV diverter primarily.

The Gas option may be simple, any many people like that option. But it is not a transition fuel.

Agree that heat pump hot water units look expensive and unlikely to last.

georgea

49 posts

Geek

#2572097 22-Sep-2020 14:23

Thanks all for the responses and info - much appreciated.

@Zeon - Reassuring to see someone else with an external cylinder

@kotuku4 - it's a restriction in width - basically we have a 580mm space, with our current cylinder being 510 diameter. Rheem's only go up to 180L in that size, and I looked at another brand which was also the same. And valid point about gas not being exactly environment friendly.

@Blurtie & @pih - thanks for the thoughts on Gas, great to get some real life perspectives, and an example of usage. I do get the feeling that there isn't really much difference running cost wise between a modern electric cylinder and LPG bottle gas system, so I think it mainly just comes down to the other factors. Also I am surprised there isn't more smarts built into these units to detect when gas stocks are low and auto-reorder (or at least forecast and alert you through an app) - but that does make me sound lazy eh!

Scott3

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#2572200 22-Sep-2020 16:03

I'm not a fan of low pressure systems so I would cross that off the list.

Putting a new cylinder in the same space is worth serious consideration. This will likely result in the shortest pipe runs which will give quicker hot water at the taps which is both convenient and wastes less water. It would be tempting to see if you can fit a larger (250 or 300L) cylinder in the same space. In some brands (Rinnai) going from 180L to 250L is the same diameter, but taller.. In other bands like Rheem going from 180L to 250L means a shorter, but fatter cylinder. If you get a bigger cylinder, you could look into something that has dual thermometers and elements (if you ever get solar (PV or thermal), you can use the top element on (Grid) electric to keep the water at a safe temperature, and mean you don't run out on sunless days. A basic indoor cylinder typically has a 10 year warranty and should last 20+ years.

Heat pump systems are getting a lot more popular these day. (especially outdoor cylinders with the heat pump integrated to the cylinder) Still should expect a good decades service out of them. Generally they are 300L. Some systems even advertise operating down to -10 degrees, so no need to booster elements:

https://rheem.co.nz/assets/Brochures/f3cc4810ed/Brochure-Rheem-Sanden-EcoPlus.pdf

Obviously capital costs are a lot higher. I would't expect the 67% -80% power savings advertised, but even 50% would be good. I havn't owned such a system, but I doubt noise is much different to that of modern space heating heatpump outdoor units. Regarding lifespan, the above system has a 6 year warranty, so I would expect to get 10+ years life out of it.

Regarding LPG, $125 for a 45kg cylinder works out to 20.3c/kWh (or 22.6 c/kWh of useful heat if burnt 90% efficiently), more expensive than electricity in many area's (assuming a standard user plan). In my opinion gas only really makes sense if you are connected to natural gas (cira 7c/kWh). Also note that gas water heaters don't last as long as their electric equivalents. As an example Rheem units have domestic 10 year warrenty on the heat exchange and 3 years on everything else. Generally they are really nice, but suck in some situations (like if you want to a dribble of hot water from a tap, or if you have a washing machine that pluses hot water feed on and off to meter warn wash temperature.

External electric cylinders are getting more common too. I don't know too much about them.

Scott3

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#2572202 22-Sep-2020 16:12

georgea:

@kotuku4 - it's a restriction in width - basically we have a 580mm space, with our current cylinder being 510 diameter. Rheem's only go up to 180L in that size, and I looked at another brand which was also the same. And valid point about gas not being exactly environment friendly.

As you say, Rheem's 250 & 300 are 580mm in diameter which means zero clearance so likely unworkable.

Rinnai has 250L and 300L cylinders in a 550mm diameter in their Stainless steel mains pressure range which gives a little clearance.

https://rinnai.co.nz/HWC#technical

GregV

844 posts

Ultimate Geek

#2572203 22-Sep-2020 16:13

Is Natural Gas from the street an option for you, or does it have to be LPG bottles? Considering this process myself.

halper86

285 posts

Ultimate Geek

#2572220 22-Sep-2020 17:26

GregV:
Is Natural Gas from the street an option for you, or does it have to be LPG bottles? Considering this process myself.

I’m guessing there will be a high install cost for this, why the OP hasn’t mentioned anything..
-e- https://www.thegashub.co.nz/get-connected/free-connection I take that back

mdf

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#2572221 22-Sep-2020 17:31

halper86:
GregV:

Is Natural Gas from the street an option for you, or does it have to be LPG bottles? Considering this process myself.

I’m guessing there will be a high install cost for this, why the OP hasn’t mentioned anything..
-e- https://www.thegashub.co.nz/get-connected/free-connection I take that back

Snap. Was just about to post the same thing.

FWIW, we're on reticulated gas and infinity hot water. We also use gas for central heating and the stovetop. The orthodox view is that gas has a relatively high daily charge but low per unit charge. You will pay more if you use a relatively small amount of gas, but save if you use gas as much as possible over electricity. Infinity hot water is *awesome*, though I do agree with previous comments about sub-optimal-ish-ness if you only need a little bit.

georgea

49 posts

Geek

#2572287 22-Sep-2020 18:00

GregV:

Is Natural Gas from the street an option for you, or does it have to be LPG bottles? Considering this process myself.

We don't have reticulated gas available at my location, so has to be LPG bottles.

bfginger

1161 posts

Uber Geek

#2572452 22-Sep-2020 23:47

Our house was built in 91, on mains water, but a small hot water cupboard that can only fit a 180L cylinder which is currently low pressure. But our pressure isn't too bad. Our tapware is newish and good quality.

3cm clearance would be tight.

It may not be wide enough for the standard larger sizes but the last time I looked you could have a custom larger size made that goes upward instead of outward.

The old tanks had 1 or 1.5kW elements. You can get a 3kW element as standard in newer tanks and solar/heatpump ready ones can usually have a second element fitted too. Some can take 6kW elements. They're much less likely to run out with a bigger element.

PolicyGuy

856 posts

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#2572508 23-Sep-2020 08:46

I have had (in different houses) hot-water-cupboard electric hot water, gas storage outdoors (like this one https://rheem.co.nz/products/home/gas-water-heating/outdoor-gas-storage/850360n0z), and continuous-flow gas (Infinity-type) hot water.

It may sound counter-intuitive, but a storage system that does run out is actually an advantage when you have teenagers - otherwise the little blighters will stand under the shower until the gas field runs out! The gas storage unit specifies "175L p/hr hot water recover", so it goes from cold to 'enough hot water for Dad or Mum to have a shower' in 30 minutes or so.
Also these units are much more energy-efficient than the continuous flow systems. If you ever see a continuous-flow system taken to bits, the heating mechanism is just a short truncated code with a single turn (or maybe turn and a half) of water pipe round it the water is not in contact with the heating element for very long at all, so it has to get a lot of heat put in really quickly, with the result that the vast majority of the heat goes straight through and out the top. This uses a lot of gas and gives you giant size carbon footprints, whereas a storage system has a much longer gas exhaust path, much more contact with the water storage and much more efficient heating - much smaller carbon footprints.

I currently have an Infinity continuous-flow gas water heater. It's fantastic, but when it fails (or earlier if I get some money) I will replace it with a heat pump electric system, powered largely from solar panels. It will probably have a longer pay-back period than my expected lifetime, but I will rest easier knowing I have vastly reduced the CO2 I'm putting into the atmosphere.

Gas is fabulous, but it's not the fuel of the future, particularly in NZ where even our mains electricity supply is 85% renewables.