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Earlier this year (during lockdown no less) my old Rheem gas 135L storage hot water service exploded into a million pieces so I had to do something to get my non-cold showers back. This is in a Melbourne climate where our hot water systems are mounted outside against on the side of the house.
I've often felt like we're spoiled in the modern age and having a big tank of water maintained at 70 degrees 24 hours a day is probably excess to what we need to be happy in life. But all the instant gas systems on the market are overkill too! I didn't want to upgrade my gas main to be able to run a 26L/min continuous flow system. What the hell am I supposed to do with a 26L/min flow rate through my hot water pipes? Can my plumbing even handle that much?
I ended up getting the cheapest possible instant electric water heater by express post via eBay. I removed my old system and hooked it up to the existing plumbing connections using flexible hoses at first, but later I was happy enough that I used copper pipe fittings and lengths of copper pipe salvaged from the old installation and made it permanent. I also capped off the old gas connection for future re-connection when I get tired of this solution.
This was a case of second-time-lucky for me. These systems are made in China and meant for sale in the Philippines (even came with a warranty card for the Philippines) for hooking up to a shower head since many there don't have central hot water. They are made with poor quality control. I paid $35 for the first one and it exploded due to a water hammer in the pipes (couldn't handle sudden surge of pressure), so I bought a second one from a different seller, this time for a cheaper price of $29 and added an inline pressure relief valve (extra fitting with red lever screwed onto the inlet in the pic). It's been 1.5 months and no issues so far. I also had to open it up in order to silicone around the top, left and right seams of the case because out of the box these aren't really waterproof as the manufacturer claims (they sell these with a fake IP rating for waterproofing, but water gets inside and stays there) I left the bottom un-sealed and drilled an extra hole in the plastic for drainage.
The main drawback with this system is that you have to adjust the inlet valve that runs into it to limit the flow rate that you get at the hot taps inside the house. It can only handle a rather poor flow rate (only about 2L/min but my low-flow shower head handles that well enough) otherwise the heating element can't 'keep up' and the water is cold. This gives me about 40 degree water straight out of the hot tap, and if I want it hotter in the kitchen I turn down the hot tap so that the water moves through the water heater slower (this gives me just over 50 degrees for washing dishes).
Pros and cons
Economical: This solution has an INSANELY low total-cost-of-ownership if you only have modest hot water requirements. I use 10-20 minutes of hot water per day and I've calculated this adds up to about 10-20 cents of electricity per day. At that rate I can use this system for about 15 years before I've spend what it would have cost just to only *purchase and install* a 'proper' hot water service (before even factoring in the usage costs).
I would NOT recommend this system unless you're happy with a very low flow rate (this also means waiting longer for the hot water to reach your tap), having the water temperature dependent on how much you turn your hot tap on, don't care about filling a bath, or have fussy family members (the above factors would drive them insane).
But for me it does just fine and there's a certain satisfaction in doing more with less. Hot water systems aren't built to last anymore and this is my way of sticking it to the 'big hot water' mob.
Also if you don't have a 15amp outlet handy to power it from, you're out of luck, since it draws a lot of amps when you turn the hot tap on. I suspect it draws more current than the manufacturer claims too.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 10:17am 15 Aug 2021
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Very interesting.
I was only saying to the Mrs yesterday that I have a tank up the back I could put under the sink to save having to wait about a minute for the hot water to arrive at the kitchen tap. Been wanting to do that since we got here. Our Kitchen is huge but she didn't want to loose the Cupboard space with a tank under there. My wife is like a gas, completely fills every space no matter how large it is!
One of these may be ideal. There is a power point right there for the dish washer and as these things are 3000W, could be hard wired into that circuit. Just have to tell her not to run the Kettle or toaster at the same time.... Hmm, maybe I'll turn it back a bit on a PWM cause I know the warning would be heeded till the first time she wanted hot water while making breakfast.
My first thought with these was how much hot water could the thing produce for a shower? It takes a LOT of power to heat water on the fly. You addressed that. Myself, I installed a LARGER diameter pipe out the hot water tank after we got here because I wasn't happy with those flex hoses that have some pitiful 6Mm bore or something and I put on the biggest shower head I could find.
I take great comfort in a long, hot, PLENTIFUL shower and although I'm a tight arse, that's NOT something I will scrimp on. All our water goes to our own treatment system which is pumped on the garden or I put in a tank for watering so we get to use the water twice anyway. To me the house use is essentially free.
I wonder how these heaters would go run in series? They would have to be run from separate circuits but I can do that from separate phases for good measure as well. If they didn't cut off with the water INLET being too hot, should be possible to get a good flow at a good temp.
My electric 400L storage heater can loose over 3 KWH a day just sitting there. I have read gas heaters use quite a bit of gas on the pilot light which goes with what they loose through convection up the flue on the storage heaters. The water is in contact so there is a draft created from the air being reverse heated which is lost... or offset by the pilot light.
Some years back in my old house which I knew I was soon going to be moving from, my old electric heater that I had patched and patched, split it's side. It was early summer and I thought cold showers wouldn't be so bad. First one proved the fallacy and stupidity of that thought.
I had an old gas storage heater up the back I had been playing with. Removed the gas burner and put one of my oil burners under the thing. Connected it up with some hoses to the heater inlet/ outlet in the laundry and ran them out to the verandah where I had this heater and fired it up. As it got to heat I had everyone pre prepared for their showers. I was blowing maybe 50Kw of heat through the thing and it kept up perfectly.
Only problem was the first night I was putting too much heat through it and between bathroom customers drying off and changing, the thing overheated and blew off on the safety valve... and what a steam show that was!
Next night I throttled it back and we all took the longest, hottest showers we ever had. The old heater was also 135L and just wasn't enough. For the first time The kids could shower till they were shrivelled up prunes and not worry. It was a Luxury we all enjoyed.
We did that for a week till I found another heater cheap which was a 50L but I put that one on the normal power for fast as possible recovery. Was a Pain but I wasn't spending $1000 on a heater for a house I would be moving out of in 6 Months. Got asked a few times If I could just rig up the other heater as a one off again cause the women could never wash their hair properly before the water ran out they reckoned.
My fathers neighbour, a Miser who spends more money on cost saving ideas than what they save, installed a caravan type instant gas water heater. He's had that maybe 2 years now and seems happy with it. Not as elaborate as yours actually plumbing it in, his sits on the back verandah and runs off the garden hose with the shower head hose going in the window.
He runs it off a 9 Kg gas bottle and says it lasts him a good while and the showers are plenty hot. I'll bet he does not shower long ( but then again since installing 30Kl worth of water tanks and plumbing the house into those, maybe he doesn't rush too much) but unusually, I have found him to be quite honest with his failed ideas so I tend to believe him when he says it's Hot and economical. Certainly there is much more power to be had with gas than electricity. He has pretty much covered his house and shed roof's with panels now so lived it up last summer and turned the electric heater back on.
Perhaps if you decide to stay with the alternative water heating ideas this would be something worth considering?
A few of us here have also been looking at direct solar heating of water tanks with PV. This may also be something helpful to you? Pre heat the water from the solar and then run it through your heater. Even if you got a 20o rise in the tank which wouldn't be hard, that would give you a higher flow rate or temperature or trade-off of both.
Quick calc shows that a 135L tank will get a 30oC temp rise with about 1200W in 4 Hours. Now you would get a ramp up and fall off of power as well which might add up to another 2 hours worth of full heating so you should get that tempo rise easily in winter with 2Kw of panels and you'd not need the electric heater at all in summer.
This is perfectly legal to do if you are the pedantic type because the solar would not be grid connected. I take it that would not be a concern though given what you have now wouldn't be exactly Kosher either so might be something a DIYer more interested in different ideas would look at.
If these heaters will take say 30o inlet temp ( and I have in the back of my mind I have read of some that won't take very high inlets for some reason) then you really couldn't go wrong. At very worst you'd be down to your limited temp/ flow, at best you'd have a full flow steaming shower for a good long time.
Tony made a controller, others have done them here and I made a very rudimentary one that seems to work. You can also Ohm match the panels and the heater that gives satisfactory results but for a typical 3600W element, you are confined to 4x 250w or thereabout panels limiting your input. Even that though will be a worthwhile increase in the water temp.
Even with just a Kw input, in summer you are still going to get the water temp up to all you need for a shower and that is all you want. And before anyone chimes in, Yes, I am aware the tanks supposedly have to be heated to a Min temp once a week to stop legionella but I have also read that does NOT apply to the sort of " sealed" tanks we use. You'd need to look that up and confirm it specifically but I seem to remember that was bit of a wives tale. In any case, if you didn't shower one day or even took a short one, you'd probably hit full temp. You will need a solenoid or Mosfet on the thermostat though as the installed one won't take DC input but you can use it as the switch to trigger the mosfet or relays. I bought some huge ones that will do 500A DC @ 1000V or something ridiculous for $40 ea recently which would walk that job in.
I'd start looking for a tank at the scrap yards. I have 3 GOOD electrics up the back atm I got from my local scrappy. One, just a 25L, was only one year old when I picked it up. I would think it probably came out of an office or factory or something but the price was exactly Nil so I am not complaining. I also have a 150? I think it is. few years old and the only think wrong with that was the element which I swapped with another element I got from the rusty tank that was sitting beside it at the scrappy. Works perfectly as well. I run them off solar in summer with the thermostat by passed to boil the water which I pour round the garden as weed killer. Does a great job especially on those pesky Bulb type weeds that keep coming back no matter what you do. I have eliminated them from my garden now.
I'll look at some more ads for these heaters and see If I can find the measurements. Only problem I can see is they might be too tall to fit under the cupboard. Other than that, for the price, how could you go wrong... even if they are a bit more exy now from what I can see.
Thanks for the heads up. Wasn't aware of these and they could be quite useful.
All good in theory, under the sink would actually be a better spot for mine too (the kitchen sink in my house is actually closer to the bathroom and laundry than the hot water service spot is), but I don't think these cheaply-built things can be trusted, unless you look around for a more reliable model. As mentioned, the first one I got, the blowoff valve randomly popped, and I was VERY happy I hadn't installed it indoors when that happened! When the blowoff valve pops it spurts water everywhere since the valve is mounted half-inside and half-outside the plastic case
I also think these draw more than 3000W. Their power rating, if you can trust it, is quoted at 220V and assuming it obeys P=V*V/R (from ohms law and P=IV), then with the same element resistance that power draw would be quite a bit higher when the same system is run at 240V instead of 220V; maybe it would jump up nearer to 3500W. I'm also pretty sure my second one is producing more heat than the first one did, so they might not be sizing their heating elements too carefully in the factory anyway.
I was also thinking of running these in series, or maybe parallel, to improve the flow rate (but I only have one 15A power outlet handy outdoors). They have a thermal safety cutout which limits them to 55 degrees so parallel might work better.
The flow rate issue is that if you turn on the valve just a little bit too high, you still get a temperature rise out of the higher flow rate but it then only feels lukewarm (something to do with how we feel temperature I guess). When I turned up the flow rate too high I got 30 degrees coming out at the tap which barely felt warm to me, while adjusting it to give a rise to 40 degrees felt hot. So it took a fair bit of getting used to at first, before I found the sweet spot flow rate that gave me a shower I was happy with. Again, the usable flow rate is a weaker flow than you'd get from a mains pressure tank and I don't use the cold tap at all since the temperature rise is lower; the low-flow showerhead does a good job with it though.
rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852
Posted: 12:07pm 15 Aug 2021
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Good job danielkos ... always worth trying out an alternative if you get the chance.
I'm in the same boat as Dave, where the hot water in our kitchen takes a couple minutes to get to a reaonable temperature. So much for a modern home with an instantaneous gas HWS.
It is also painfully slow to deliver hot water in the bathrooms too ... but we've had to put up with that ... although being able to dial in a temperature on the control and not have to fiddle with the cold tap is very handy.
I got so sick of the situation in the kitchen that I bought a heater similar to yours and fitted it under the sink. It is dodgy in that you have to turn on the hot tap fast (I assume to trigger the thing to start heating) ... and then back off to a fairly slow rate so that it has time to get some heat in the water ... and it is sort of acceptable.
Certainly better that what we had before ... but still so inconsistant with the output temperature.
Sometimes, even with just a trickle it is barely luke warm ... and other times you can scald yourself. Mine has a knob on the front which I assumed was there to adjust the output ... but it really seems to do what it wants and pays no attention to where you set it.
I'd also like to put one in the ensuite ... but of course there are two basins in there ... so that'd mean two units ... and then the main vanity at the other bathroom has two basins and I just know I'd be expected to fit two there as well.
The one in the kitchen has been there maybe 3-4 years already ... and apart from the inconsistant output temperature has been very helpful.
It's amazing what we put up with really. Before we came here we were in a 70 y/o stone home with an old electric HWS. It took literally seconds to have hot water in either the kitchen or bathroom ... yet here we are with this nice posh joint and it's like we're living back in the 1920's.
Our house is on rainwater too ... so it goes against the grain to run the taps for 1-2 minutes everytime we want a bit of warm water.
I took half a dozen photos but the second digit still wouldn't show up ... it's supposed to show 34.
Cheers, Roger
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 01:30pm 15 Aug 2021
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I had not thought of that. I assumed ( stupidly) that they would be like regular heaters and the blow off could be Piped to a drain. Even my outdoor heater had that when it could go to the ground with no trouble.
Hmm, 240 is low here. Of course they blame it on solar but not a lot of that in the grid at midnight and 3am here when I have seen it at 250 and more than once. I have a fan heater running now and the power meter on it tells me the voltage is still 232 with that running. Why am I not surprised?
Yeah, that's the trouble, Chyneese quality is so hit and miss. I bought some of those heaters like you put in a coffee cup last year for a project. Bought 3. 2 died in no time, the last one was fine even though I ran it half dry a couple of times and did other things I would have expected to make it fail. Bought a couple of others and wasn't game to plug them in! My god some of their standards even with mains power are atrocious. Gave the seller a BIG serve, got a refund and reported them to fleabay and the electrical stds mob whom were a challenge to find and whom looked after that seller. I would bet my house even though they were an Oz based seller they did absolute Jack about them.
Yes, 55 is plenty hot and if you got a decent flow rate at that, you wouldn't need anything else.
The shower in my first house was like that. I don't know what thread pitch the taps were but I think it was about 3" per turn! I tried replacing the washers and the shower head but to change the taps would require pulling the wall out then re tiling the whole bathroom to match and..... Ugh.
Made me want one of those fancy gad setups I have seen where you put in the exact temp you want and that's what you get. That would be heaven!
I replaced the shower head at my last place and it had a low flow restrictor in it. I couldn't stand it. I was always cold through not enough water to the point I had it so hot I was burning myself... and still feeling cold. I took the thing out and then it was fine. I think it must have been flowing about 1L / min. Was terrible!
The Big square one I put on here had the same thing which seemed Nuts. Why have a huge shower head when the flow rate is not enough to go across all the holes? Removed that then the flow of the hot water couldn't keep up which I traced back to the stupid straw diameter pipe. Did it properly in copper and no more worries.
I noticed the fact you insulated your Pipe. I'm amazed how many systems I see that don't have that or a useless green thin bit of plastic. having the pipe insulated can make a measurable difference to water temp. Mine wasn't insulated when I came here. I got that thick foil backed foam they use in AC and did mine including the Blow off valve which was always hot and leaching heat through over a meter of copper pipe. Stupid! I replaced that with a short bit of plastic so the thing wasn't drawing heat all the time and radiating it to atmosphere. Can undo a bit of the insulation I closed with Velcro over the valve to Burp the system if need be.
Just use a 15mm BSP tee connector on the heater outlet and then hook up the hot water to both basin mixers from the same tee connector. Unless you're often planning to run both basins at the same time of course.
'Sort of acceptable' sounds about right, lol, also the luck of the draw (my second one senses the flow better than the first one did, and has a better temp rise despite coming out of the same factory).
But when I first hooked mine up with hoses rather than rigid pipes I think I noticed a bit of 'surge flow' when turning the water on anywhere in the house, due to the hoses being a bit elastic and getting the pressure released from the hose downstream from the heater before it started flowing from the heater itself. My theory was that the pressure in the hoses was producing a bit of "push-back" (how to describe this?) when I turned the tap on and this might have impeded the flow sensor from turning on. Seems like a bit of a black art.
It might be worth opening yours up to see if that knob is actually connected to anything or just a placebo? I can't imagine having an electrical thermostat on something as simple as a heating element.
Another possibility: maybe that temperature knob is really just a flow regulator designed to reduce the flow so that the water reaches a higher temp when it runs through?? Edited 2021-08-15 23:46 by danielkos
That's why I added a proper relief valve at the inlet, which is more like the type on a regular hot water tank (except an inline version, more cheaply made and from ebay), because the blow-off valve that comes fitted is the worst thing you can imagine. It's like they got a narrow plastic pipe end, plugged it with a rivet and slipped a loose sleeve over it. When it blows, it means the 'plug' has burst off, which pushes the sleeve out and gives you a visual indication that it's blown inside. And then that's it, it only spurts water everywhere from that point forth! It's a pressure relief valve that's good for one time only. The relief valve I added lets out a few drops of water at a lower pressure so hopefully will save that 'emergency' blow-off valve from ever blowing.
Part of what made me go this route was at the start when I was looking online for an installer to change over my hot water system to a regular replacement. The installer websites show you a big price tag or big phone number, have a stock picture of an attractive woman smiling at a male plumber like she's won the lottery, a promise that you can turn your brain off if you call this plumber and they'll make your troubles go away, and a picture of the finished product with NO INSULATION ON THE PIPES! So I wanted to find a quick-fix way to do it myself, not to save money, just out of sheer rage
I also found manufacturer pics of instant gas systems with thermal lagging on both the inlet and the outlet and I didn't understand at first why you'd want to insulate the cold supply line rather than just the hot. Turns out putting thermal lagging on the cold inlet is important too because these things only give a relative temp rise unlike a tank, so if your ambient cold supply is about 13 degrees (as mine usually is, it comes from underground of course) and it's only 5 degrees outside, that cold pipe is losing heat and reducing the final temp.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 02:51pm 15 Aug 2021
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Like I have seen pics of Solar installers and Panel Cleaners STANDING on the panels. I had a jibe at one installer on a forum who's advertising featured a couple of such pics as he was holding himself out to be a quality installer. When I pointed out the huge flaw in the pics He whom arced up and said it was only a stock Pic. I said if he were stupid enough to use that pic to promote his company's services and couldn't take a better one on a real job, then they were just as slipshod as the Pic implied. In reality I think they didn't see anything wro9ng with the pic and probably walked on the panels and I'm talking in the middle rather than on the frame edges because that's what they did in practice... like the Plumbers doing HWS.
Well you sure got me there! That never occurred and here it's easy to get below zero.
That said, the pipe run into the heater from the valve is so short it would be hard to insulate and the area and volume it could loose heat is very limited.
The point is well taken though. I actually thought of it from the heat radiating back out the tank but figured the losses would be minimal with the pipe so short. Might have had something to do with the temps here and using that flexible braided runner hose.
One thing I have noticed, 2 actually. The water temps here are much more stable than my other homes. I suspect because this place is brick and better insulated. The out of the mains temps should be pretty stable given the depth they are sunk and the geothermal temps. Probably when it enters the premises the temp changes as you espouse to.
Other thing is we used to get Frozen pipes here in winter. Sometimes you couldn't get water out of certain taps till 10 am and the neighbours said theirs took Longer. I would leave a couple of taps drip or have a fine trickle at night so the water was always moving somewhat.
I have heated the house quite a bit the last 2 winters especially trying to keep the house stable rather than cycling this winter and haven't had a hint of a frozen Pipes. Didn't get that many frozen mornings but there were a couple of weeks there where defrosting the vehicles every morning was required because the wipers were stuck fast to the windshield. Was only a couple of weeks ago where the birds were landing on the birdbath outside my window and walking clear across it being frozen solid still at 10 am.
I believe having the house warmer even though a lot of the pipes which are in the roof run ABOVE the insulation is keeping them warmer and stopping the freezing.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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