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Old 01-30-2019, 09:09 PM   #1
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Tankless Water Heaters

So I know everyone is different on what you "just must have" in your bus if you're going to be spending any significant time in it. One thing I don't want to give up are my long, hot showers. The other day I decided to do the numbers and timed my "normal" shower, and checked the water meter before and after to see how much I had used. I have a 40g. water heater. My shower was 15+ minutes and I used 36 of the 40 stored gallons before it starts to cool down (2.4g/min).
So my questions to those who use tankless water heaters are:
1) How hot can you get steady water?
2) How long will it supply that hot water?
3) Is my limitation the size of my fresh water tank?
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Old 01-30-2019, 09:54 PM   #2
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Quote:
Originally Posted by o1marc View Post
So I know everyone is different on what you "just must have" in your bus if you're going to be spending any significant time in it. One thing I don't want to give up are my long, hot showers. The other day I decided to do the numbers and timed my "normal" shower, and checked the water meter before and after to see how much I had used. I have a 40g. water heater. My shower was 15+ minutes and I used 36 of the 40 stored gallons before it starts to cool down (2.4g/min).
So my questions to those who use tankless water heaters are:
1) How hot can you get steady water?
2) How long will it supply that hot water?
3) Is my limitation the size of my fresh water tank?
My experience with tankless water heaters is limited to those in fixed houses, but most of the same principals apply. When you are looking at gas fired tankless water heaters what you need to research is its ability to raise water temp at a given flow rate. Most of the flashy advertising specs are for very low flow (=<1.5 GPM) so do your research. In your case, you want to flow approx 2.5GPM which is standard for shower heads in the US outside of Kalifornia. The Ecotemp L10 which seems to be a popular model for skoolies is rated at 75,000btu's but at 2.5 GPM this will only raise your water temp by 32* That would be woefully inadequate in a residential setting here locally, as we have to plan for incoming water temps around 45*(worst case scenario). If your only running it off of tank water, and that water is already at 70-80* then this might work for you, otherwise you will need something with more power. The other issue with large LP units, portable or fixed, is that once you get into the 150,000+ btu range, you will need to make sure your regulator is capable of those flow rates, and you will need more than a 20# propane tank. That grill cylinder will be iced up and frozen before you get the soap out of your hair if your trying to pull 200,000btus out of it. Once you get this figured out, and get a properly sized unit, your hot water will be limited only by your water tank size, and your fuel supply.
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Old 01-30-2019, 10:02 PM   #3
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Originally Posted by Willie_McCoy View Post
My experience with tankless water heaters is limited to those in fixed houses, but most of the same principals apply. When you are looking at gas fired tankless water heaters what you need to research is its ability to raise water temp at a given flow rate. Most of the flashy advertising specs are for very low flow (=<1.5 GPM) so do your research. In your case, you want to flow approx 2.5GPM which is standard for shower heads in the US outside of Kalifornia. The Ecotemp L10 which seems to be a popular model for skoolies is rated at 75,000btu's but at 2.5 GPM this will only raise your water temp by 32* That would be woefully inadequate in a residential setting here locally, as we have to plan for incoming water temps around 45*(worst case scenario). If your only running it off of tank water, and that water is already at 70-80* then this might work for you, otherwise you will need something with more power. The other issue with large LP units, portable or fixed, is that once you get into the 150,000+ btu range, you will need to make sure your regulator is capable of those flow rates, and you will need more than a 20# propane tank. That grill cylinder will be iced up and frozen before you get the soap out of your hair if your trying to pull 200,000btus out of it. Once you get this figured out, and get a properly sized unit, your hot water will be limited only by your water tank size, and your fuel supply.
Lots of good info there, Thanks Willie
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Old 01-30-2019, 11:42 PM   #4
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Lots of good info there, Thanks Willie
+1 Thanks Willie!
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Old 01-30-2019, 11:48 PM   #5
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Sounds like my 140, 15 minute showers is a no go.
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Old 01-31-2019, 12:05 AM   #6
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Boy Marc, you would not have been a happy camper at our place on the West side.

We relied on rainwater collection for our domestic water. That made for some lifestyle changes like 3.5 gallon " Navy" showers.
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Old 01-31-2019, 08:25 AM   #7
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"3.5 Gallon Navy Showers"?


Must be the "new" Navy. We got 1/2 gallon max on "water hours"
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Old 01-31-2019, 10:59 AM   #8
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I've been pondering how I might build a recirculating shower. The idea would be to use the first few minutes and gallons of shower time getting soap etc taken care of and let that water drain away. Then flip a valve and start recirculating water for the hydrotherapy session. Recirculation would significantly reduce the need for both water and fuel while the shower drags on and on..

There are a few little challenges related to keeping the recirculated water separate from the potable water. Need a separate pump, a separate heater (or heat exchanger, at least), and backflow prevention at the shower valve or head.

Has any of you seen any cleverly simple implementation?
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Old 01-31-2019, 11:26 AM   #9
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We have one in our bus, and had one in our camper for many years. They are both Marey units. This being the gas fired on demand heater. It can be used outdoors connected to a garden hose or used inside connected to you water pump. If inside you can get it with a vent pipe connection for exhaust gases.

Our water tank is in inside the bus as we do not want it to freeze, no showers then...

Our experiance is that we can have as hot of water as one wants for a long as you have water. We have a 105 gallon water tank. A 15 minute hot shower is fully possible, and on rare occasions I have done that. Mostly tend to do "navy showers" though, although not as short as Tango mentions. We use the shower head that comes with it, and it is plenty of water. I do not know what the flow rate is, however it is more then enough for a nice comfortable shower.
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Old 02-01-2019, 07:10 AM   #10
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Quote:
Originally Posted by o1marc View Post
Sounds like my 140, 15 minute showers is a no go.
I've had my Eccotemp L5 going on 3 years, setup outdoors with stainless/rubber garden hose hooked to clothes washer and shower... I can hit 194 degrees as long as I want, by manipulating a ball valve on the inlet side, or the one on the outlet side. I have great city water pressure, so I'm just slowing the flow. And the flow is negligible from the shower head itself.

I've done the exact same steps using the 12v pump from harbor freight and a 55 gal poly drum. Same results.
Only limited by the amount of water or propane you have.

and I've done it this way for years!
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