Solutions for long hot water delay to kitchen.

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Paul1977

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#285926 26-May-2021 09:53

Our house uses gas for hot water, but the design of the house means that the kitchen is a good distance from the gas califont. This means an annoyingly long wait to get hot water in the kitchen. A bit of a delay in other areas isn't a big problem, but in the kitchen it really annoys us.

What's the best (not too expensive) solution for this?

I think we'd have room for an underbench water cylinder, but have a few questions about this idea:

How big would we need to not risk running out of hot water?
How long do they take to heat back up if you do run out?
Can it be configured to automatically switch back to gas if it runs out of hot water?

Or would a small electric instantaneous water heater under the bench be better?

Thanks

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#2713111 26-May-2021 10:00

Another idea to consider is to Insulate the pipe, so it takes less time to heat up the cold pipe.

chevrolux

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#2713116 26-May-2021 10:15

Yea those little under bench hot water boilers are pretty great. Will mean a tap swap. But you can have hot, and then also boiling water on demand.
They aren't super cheap, but I wouldn't say they are that expensive either for the convenience.

Paul1977

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#2713122 26-May-2021 10:30

chevrolux: Yea those little under bench hot water boilers are pretty great. Will mean a tap swap. But you can have hot, and then also boiling water on demand.
They aren't super cheap, but I wouldn't say they are that expensive either for the convenience.

Was hoping to not need to swap taps. We already have an Insinkerator Multitap for boiling water, so I was hoping we code get something to just replace the standard hot feed to the existing multitap. Is there anything that could do that?

Electric instantaneous may not be an option as I just looked up the power requirements, and I think most cylinders/boilers require venting of some kind?

@chevrolux Do you have a link to the type you're talking about where the boiler provides both hot and boiling and would replace the current tap?

Bung

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#2713124 26-May-2021 10:36

How much cold water would you collect in a bucket before it runs hot? If you have most of the hot run in 20mm pipe that's a lot more standing cold you have to replace that if you had the kitchen run directly from the water heater in smaller diameter pipe.

Paul1977

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#2713130 26-May-2021 10:53

Bung: How much cold water would you collect in a bucket before it runs hot? If you have most of the hot run in 20mm pipe that's a lot more standing cold you have to replace that if you had the kitchen run directly from the water heater in smaller diameter pipe.

@Bung I have no idea, I'd have to do it to see.

I'm not sure what diameter the pipes are, what ever is standard I guess. I don't see that it would be possible to replace the entire run from the califont to the kitchen since some is inside walls and under the floor. But a good deal of it is in the roof space (not sure how easily accessible).

You sound like you have a better idea about plumbing than me. Would it potentially make a difference to replace just the portion that is accessible in the roof space? I wouldn't have thought of this, but it makes sense.

How narrow a pipe could you go to a single tap before you compromise the flow rate?

esawers

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#2713135 26-May-2021 11:07

We have a 1940's subfloor, the plumber just ran a more direct pipe route from the gas hot water to the kitchen sink.

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Paul1977

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#2713136 26-May-2021 11:12

esawers:

We have a 1940's subfloor, the plumber just ran a more direct pipe route from the gas hot water to the kitchen sink.

Our is direct, it's the distance that's the problem for us (potentially combined with the pipe diameter).

SirHumphreyAppleby

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#2713138 26-May-2021 11:18

I would think a hot water recirculating pump would be the best option. Save that precious under-bench space.

I'd also look at insulating/replacing the existing pipe regardless of the method chosen.

Zeon

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#2713141 26-May-2021 11:35

Our hot water cylinder is located ~10m from the house outside with (currently) non-insulated copper and plastic piping going to the house. Run to the kitchen is probably 25m copper/plastic pipe. We have a pump that can do 180L per minute and no flow limiter on the sink tap. If we just let it run with normal watercare pressure/flow rate it would take maybe 40 seconds to get warm. Simple solution is go full bore at 180L/minute and its warm in about 5 seconds.

You need a tank and pump to do this though and not sure it would help with as-you-go gas water heating which I doubt can heat 180L/minute.

I was thinking of putting like a small button in with a return pipe to our water tank so we wouldn't waste that water. I.e. press a button valve and it sends the water from hot and back to the cold water tank. Might do it during renovations.

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Paul1977

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#2713142 26-May-2021 11:44

SirHumphreyAppleby:

I would think a hot water recirculating pump would be the best option. Save that precious under-bench space.

I'd also look at insulating/replacing the existing pipe regardless of the method chosen.

I don't understand how this would be a good option with an on-demand gas water heater? In fact, I'm not even sure how it would work for that?

Inphinity

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#2713151 26-May-2021 12:23

Zeon:

You need a tank and pump to do this though and not sure it would help with as-you-go gas water heating which I doubt can heat 180L/minute.

Unfortunately not, most of the residential-grade gas instant hot water units are rated to heat between about 15 - 35L/min with a 25*C temperature increase from intake.

Watercare only commit to a flow rate of 25L/min for residential connections anyway - it could be higher, but that's their standard. Higher flow rates work with a tank where you can 'pre-fill' 180 - 300L or so with a standard water cylinder.

As to the original problem, we looked at a similar situation when installing instant gas hot (though we ended up relocating the main unit due to other factors that meant it wasn't such a problem in the end) - and were suggested having a 15 - 20L underbench hot water cylinder, fed by the instant gas hot rather than my the cold feed.

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Paul1977

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#2713162 26-May-2021 13:00

Inphinity:

...and were suggested having a 15 - 20L underbench hot water cylinder, fed by the instant gas hot rather than my the cold feed.

I'd thought of that as an idea, but don't cylinders need venting? If so, how could this be done in a retrofit into an existing kitchen island?

SirHumphreyAppleby

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#2713176 26-May-2021 13:50

Paul1977:

SirHumphreyAppleby:

I would think a hot water recirculating pump would be the best option.

I don't understand how this would be a good option with an on-demand gas water heater? In fact, I'm not even sure how it would work for that?

Hmm... I thought I'd answered this. Must've got distracted.

From what I've seen, these systems recirculate hot water either via a dedicated return path or using the cold water line (via a valve). Water is taken from the 'hot' on the tap and sent back to the heater, so the heater is simply heating water passing though it, exactly the same as if the water had come from the town supply or a tank.

These systems seem to be controlled via either a button or sensor, depending on how much gas you are willing to waste just to have hot water without a delay after turning on the tap. E.g. You may press a button 20 seconds before using the tap or use a sensor to circulate the water when motion is detected in the kitchen.

If you were using electric heating with a thermostat keeping the water in an acceptable range, you could probably just cycle a pump on and off periodically to achieve the same thing.

Paul1977

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#2713207 26-May-2021 14:10

SirHumphreyAppleby:

Hmm... I thought I'd answered this. Must've got distracted.

From what I've seen, these systems recirculate hot water either via a dedicated return path or using the cold water line (via a valve). Water is taken from the 'hot' on the tap and sent back to the heater, so the heater is simply heating water passing though it, exactly the same as if the water had come from the town supply or a tank.

These systems seem to be controlled via either a button or sensor, depending on how much gas you are willing to waste just to have hot water without a delay after turning on the tap. E.g. You may press a button 20 seconds before using the tap or use a sensor to circulate the water when motion is detected in the kitchen.

If you were using electric heating with a thermostat keeping the water in an acceptable range, you could probably just cycle a pump on and off periodically to achieve the same thing.

Right. Seems like it would potentially be very wasteful in terms of gas to constantly loop the water so it's always hot near the tap. The idea of pressing a button before running the tap would save wasted water and gas but you'd still be waiting the same time from pressing the button to when you receive hot water. And we go into the kitchen a lot without using hot water, so a motion sensor would surely be wasteful as well.

I can see how this would be a good system in conjunction with a hot water cylinder, but it just doesn't make sense in my mind for an instant gas system.

Scott3

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#2713217 26-May-2021 14:39

Paul1977:

Our house uses gas for hot water, but the design of the house means that the kitchen is a good distance from the gas califont. This means an annoyingly long wait to get hot water in the kitchen. A bit of a delay in other areas isn't a big problem, but in the kitchen it really annoys us.

What's the best (not too expensive) solution for this?

I think we'd have room for an underbench water cylinder, but have a few questions about this idea:

How big would we need to not risk running out of hot water?
How long do they take to heat back up if you do run out?
Can it be configured to automatically switch back to gas if it runs out of hot water?
Or would a small electric instantaneous water heater under the bench be better?

Thanks

Given you already have a boiling water unit, and (hopefully) have space for a separate under-bench hot water cylinder, the latter is likely to be a better bet than a combined unit.

Without knowing how much water you use in the kitchen, no way of answering how big you need, but they seem to be available in 15, 25L and 40L.

https://rheem.co.nz/products/home/electric-water-heating/low-pressure-copper/19901513

https://rheem.co.nz/products/home/electric-water-heating/mains-pressure-vitreous-enamel/31202519v

https://rheem.co.nz/products/home/electric-water-heating/mains-pressure-vitreous-enamel/31204515

Recovery rates on a 50 degree rise are

2.0kW: 34L/hr
2.4kW: 40L/hr
3.0kW: 51L/hr

So with the 40L, if you completly run it out, it will be fully heated again in 47mins... Obviously you need to confirm if you can get a 16A feed to your kitchen for this.

No need for a vent on these, but they do need a drain (assume you could share your skin drain pipes?).

Instant electric hot water heaters are sweet, but need some fat wiring i.e. the below has 30amp and 40 amp versions, and even then the flow rate isn't going to be great. Few NZ homes have the electrical capacity for this. My house for example has a cira 60A feed for everything... but could solution for something like a batch, with few electrical demands, only wanting hot water for the shower, not caring about low flow rate, but wanting infinite run time, and no standing losses. Could also be good in commercial /industrial buildings with ample electrical capacity.

https://www.stiebel-eltron.co.nz/dhce-50-instant-single-phase-water-heater

Short of ripping out the hot water feed pipe, and replacing it with a skinnier one, increasing the flow rate with a high flow tap or similar, or changing the entire house to a storage based hot water system with reciruclation, I don't know if you have many other soultions.

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