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Bathtub Water Heater


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Hello.

 

I'm looking for recommendations for a bathtub water heater. We have a new house, and I installed a 6000 watt Electrolux model. The house is in the north.

 

The water heater is hot enough, but it has dismal water flow. It's fine for the shower head, but at the tap it's slow. It'll take 30-40 minutes to fill the bathtub.

 

Water pressure throughout the house is strong. I installed an oversized pressure pump. Going into the water heater the pressure is fine. Coming out, it's slow.

 

 

 

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A reasonably large tank type heater would supply lashings of hot water for your tub without stressing your electricity supply, until the tank is empty of course.

 

Alternatively a gas on-demand heater will give considerably more oomph than anything electric that's not 3-phase (and even much that is) and it doesn't run out of water (it could run out of gas of course).

 

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The heat isn't the problem, it's the amount of water flowing out of the heater. I'd estimate it's about a 50% reduction in flow rate, the input line versus the output line.

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37 minutes ago, Crossy said:

A reasonably large tank type heater would supply lashings of hot water for your tub without stressing your electricity supply, until the tank is empty of course.

 

Alternatively a gas on-demand heater will give considerably more oomph than anything electric that's not 3-phase (and even much that is) and it doesn't run out of water (it could run out of gas of course).

 

 

Exactly what I plan to do, when we build our home. Likely a gas water heater. Gas here is reasonable, and it takes very little gas to heat water effectively. Massive water flow means a large tub is full in 10-15 minutes. I will avoid those ridiculously huge tubs, which work if you are having four adventurous young women over, but are not particularly practical for the average bath! 

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52 minutes ago, Thomas72 said:

Hello.

 

I'm looking for recommendations for a bathtub water heater. We have a new house, and I installed a 6000 watt Electrolux model. The house is in the north.

 

The water heater is hot enough, but it has dismal water flow. It's fine for the shower head, but at the tap it's slow. It'll take 30-40 minutes to fill the bathtub.

 

Water pressure throughout the house is strong. I installed an oversized pressure pump. Going into the water heater the pressure is fine. Coming out, it's slow.

 

 

 

Who uses a bath tub these days? Waste of water & energy = money!

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37 minutes ago, Thomas72 said:

The heat isn't the problem, it's the amount of water flowing out of the heater. I'd estimate it's about a 50% reduction in flow rate, the input line versus the output line.

 

Physics is not your friend here, double the flow rate needs double the energy for a similar temperature rise.

 

On-demand heaters restrict the flow so they can get enough energy into the water for a decent delta-t. Of course if the water going in is starting cooler then the same amount of energy will result in slightly cooler output too.

 

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All "on demand" water heater have flow restrictions, too much flow and the water will not be hot.

 

As mentioned a hot water tank, like the ones we used to have in the airing cupboard is the answer.

 

Constant ready hot water with as much pressure as your pump can deliver.

 

 

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What about a multipoint heater? Something like one of these:

 

https://www.homepro.co.th/search?q=+DHC+ILEC

 

Wouldn't a multipoint heater have better output flow?

 

I've reviewed a some gas units, and they all (mostly) have a liter/minute rating. Unfortunately, I can't find similar ratings for these electric units. A 12 or 18 liter/minute gas unit would do the job, but it's a bit more work to get it all set up. I'd rather go electric if possible.

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Installing a tank would of course work, but this is just for 1 of the 3 bathrooms in the house, and only for the bathtub. This is for a jacuzzi tub for the wife, that she'll probably use 1-4 times a month. A tank seems like overkill and not very efficient.

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43 minutes ago, Thomas72 said:

What about a multipoint heater? Something like one of these:

 

https://www.homepro.co.th/search?q=+DHC+ILEC

 

Wouldn't a multipoint heater have better output flow?

 

I've reviewed a some gas units, and they all (mostly) have a liter/minute rating. Unfortunately, I can't find similar ratings for these electric units. A 12 or 18 liter/minute gas unit would do the job, but it's a bit more work to get it all set up. I'd rather go electric if possible.

To go electric with an instant heater to get the flow rate you want needs a heater of around 20,000W or higher, they are not available and your power supply is unlikely to support 90A.

It doesn’t matter if it sold as a multi point heater or single point one it needs enough power to heat the water.

 

A gas or electric heater at 12 Lpm will take 10 minutes to fill the bath and that’s too slow.

 

For electrical heating you need a storage water heater that can put the power in over a longer period, a 3,000W heater will probably be OK, you probably need an 80 litre unit. It is far more efficient than any instant heater.

 

The ideal unit, which is probably not available here, is that standard Japanese bath water heater. They will heat the water in the bath itself to any temperature you want.

 

 

 

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I bought this unit at Thaiwatsadu. It's a jacuzzi bathtub. It doesn't have a heater.

 

I guess I'll have to go with a mini tank heater.

 

20200716_142938.jpg

20200716_142856.jpg

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Tank heater is the way to go, I think you can get a 150l pretty reasonably.

 

If the tank heater will be dedicated, and you only plan to use the tub now and again. just install a switch to turn it off and on. It should only take 15-20 minutes to get hot.

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Yeah, I think that's the only option. Although I think an 80-100L will be enough. Can crank the heat up all the way, some get scalding hot, then dilute it down with tap water.

 

Problem is, this bathroom is really small and there's no room for a tank heater. I'm going to have to install it in an adjoining spare bedroom.

 

It might be a while before I get this done. This is a new house and I have 10 projects ahead of this one. I'll come back and post some pictures once I get it finished up.

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