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Hot water

13K views 46 replies 27 participants last post by  sea_hunter 
#1 ·
I see alot of boats have hot water heaters. I think the better solution would be to have the instant hot water heaters instead of the tanks. They take up less space and are more efficient. I don't see alot of them on sailboats for some reason. It seems like an obvious thing to upgrade. Any big reasons not to use it ?
 
#2 ·
There are two types:

Electrical
Gas

Electricity is scarce on a boat. You can use it when you have connection to land and will not have hot water while cruising. Running a generator might be an option.

Gas is dangerious and will require a flue.

You can have hot water if you have tank heater. this will keep the water hot even after you use land power. Another opportunity is to heat water when your engine is running.
 
#3 ·
"Tank" style hot water heaters will often use engine coolant to heat the water. In the hot weather the water will stay warm in the tank for hours. So, it's "free" if you time it right.

If one does not shower often on board or sail in cold climates, then a water heater of any type is a waste of space.

I will admit they are nice to have. My last boat had one till it died, then it didn't. I missed washing dishes in warm water, but, I liked the extra space for batteries better :D
 
#4 ·
I see alot of boats have hot water heaters. I think the better solution would be to have the instant hot water heaters instead of the tanks. They take up less space and are more efficient. I don't see alot of them on sailboats for some reason. It seems like an obvious thing to upgrade. Any big reasons not to use it ?
Because most of them do not meet ABYC safety standards.
 
#5 ·
They all seem like good reasons. The not meeting ABYC standards probably means getting insured might be a problem. Still it seem doable if researched and installed correctly. We just recently installed one and we love it however it is not on a boat.
 
#6 ·
Depends also on your sailing area, and what you want the hot water for. I use a solar shower for bathing, and then just heat water for washing up. (I have a water heater, but it's shot, so it's basically just 6 more gallons of storage)
 
#7 ·
Well we are in Central Florida. It does get chilly here in the winter but it does not last long if it does. We are planning for the boat being a sort of waterfront condo at first. Depending on how comfortable we can make it we are considering moving aboard. Right now I am just doing research and I do not see anything so far that would prevent what we want to do. Luckily the wife and I are both pretty handy.
 
#8 ·
I think that you need to think about where and when you are going to use hotwater. If you are tied up in a marina with power, as is the case for most liveaboards then a tank heater makes most sense and is easiet and cheapest to install. If you are on the hook or rarely use your engine then the tank ones are not very useful. So if your cruising is ICW you are fine; if you are sailing long distances offshore you are out of luck unless you have a genset or need to run the engine to charge batteries (which you probably don't with solar/wind).

I have had a couple of boats with tankless, gas-powered heaters and quite like them. Caveats though, you need a marine unit not a domestic one (they exist, and are quite common in Europe, but not cheap, you need a suitable spot to install one - Hinterhoeller boast typically used them and they built the galleys so the unit was at eye level and handy ( you lose some good cabinet space here but it was easy to then build in the flue. I guess what I am saying is that they work better when they are designed into the boat not added on. BTW, I don't see a particular advantage to the electric, flash heaters - if you have 110v go with a tank. Final comment about gas heaters, ours had a pilot light (Paloma, no longer recommended for marine) but we never left the unit going between uses since it was very easy to start the pilot each time.
 
#9 ·
Just a note, electrical fires are the number one cause of boat fires. Not fuel, not propane, not the galley...... electrical.

If you are going to live aboard for any length of time, but do have frequent access to a marina, then I would use an electric tank heater that also heated off the engine coolant. You either run a genset when at anchor or the engine to top the batts anyway, so it will make hot water then.
 
#11 ·
In the summer my mainwater tank is 100degrees after the boat is sitting in the sun all day. Getting COLD water is the main problem. I don't use my water heater much.

The big problem with a tankless heater is they use a LOT of power for a short time, as opposed to a tank that uses less power 24 hours a day.

For a boat, engine power is probably the biggest source of heat on the boat, followed by gas.
 
#13 ·
The problem is that there are very few that meet the safety standards. It is not just about insurance it is about safety. An LPG on-demand "marine unit" would need to be externally vented, sealed combustion and have a myriad of other safety features.

There are a few disreputable companies out there marketing on-demand propane for boats that DO NOT meet minimum safety standards despite their sneaky marketing. Some customers have spent good money only to be later told during an insurance survey that it now need to be ripped out.
 
#14 ·
I can see that happening but if you do your research I think its possible. From what I know lots of folks have Force10 stoves and I believe they are LPG. If that is the case then it can be done as long as its done properly with the proper equipment.
 
#15 ·
Jackpal, you are beginning to seem like you've made up your mind.

Keep in mind if you install a non- ABYC device, there is simply a reason it isn't approved. Intuition isn't the reason. If you go ahead anyway, you risk all lives aboard. Poor seamanship.

I wonder what a personal liability lawyer would do with this if you caused personal injury or property damage to another. Be careful.
 
#17 ·
First up, if I was going to be living onboard tied up to a marina, i'd be using the marina facilities for showering.

That aside, water heating is a pain in the butt. When cruising we spend more time on the hook or sailing than we do motoring and have no real need to run the engine an hour a day except to heat water. Sadly, unless you insist on air con as well, it is the one area where solar and/or wind does you no good.
 
#21 ·
I've never had an instant hw heater, but this ocurrs to me. Perhaps there is more to it. In order to really have instant propane fueled hot water, it seems you would need to leave the propane lines charged through your boat at all times, which is a bad idea. You should have an electric solenoid that shuts the line down at the tank, so your bilges don't fill with propane while you sleep and that first switch ignites the boat. However, you would have to cycle it on and off each time you wanted hot water. Proper protocol would also have you purge the propane line to extinguish the flame as well. That doesn't sound so instant to me.
 
#22 ·
I had an instant water heater [ gas ] on a previous boat. It was great when we were above the latitude that the butter melts at.

No such animal now I live year round where the butter melts but I do have a solar bag water heater for the odd time that I feel the need for a hot shower.
 
#23 · (Edited)
My boat has a factory installed on-demand heater:

Yes, it has a flue (sealing to protect from green water--you MUST remember to open it), separate combustion air supply (ABYC suggests a separate sealed compartment, which it has; this is a very difficult requirement for most boats), leak detector, and flame interlock. It works well... sort of.

a. Showers always go through a lot of water, but more so when using hot water, because of the time required to heat the pipes and adjust the temperature.

b. It really doesn't work so well for galley hot water, for the same reason; the waste each time is OK at home, but unacceptable even on a boat in a marina. I end up always using cold water for dishes. Thus, I DO NOT leave the unit on unless I am taking a shower.

c. The temperature regulation is not perfect, not quite like a tank. To get steady temperature you need to let it run wide-open, which wastes more water, even for the fastest shower taker.

d. A hot shower put TON of moisture into the boat. This is never acceptable, summer of winter. While a bathroom fan helps, not enough.

Alternatives?

a.Shower ashore.

b. When on the hook in the summer, take cold showers on-deck (we have a transom shower and use it a lot). This can be done discretely in the cockpit, wearing a bathing suit for the most part. The water is not really cold on a boat, since the pipes are not underground.

c. I don't care for solar showers; if it's warm enough to work well, I can take it cold more simply.

If I were living aboard and could manage the space, I would go for a small engine-heated electric tank heater. If it had to be propane on-demand, make sure the installation is faultless. And I would use marina facilities most of the time.

---

Before you consider going for a ventless heater--the OP did not suggest this but many have in the past--realize that a hot water heater has a HUGE firing rate compared to the stove: 199,000 btu vs. 8,000 BTU. These MUST be vented in a small place like a boat. There have been several cases reported of sailors getting knocked out while showering.Propane possible boat peril One sailor died, another sickened while in shower - Baltimore Sun
 
#25 ·
a. Showers always go through a lot of water, but more so when using hot water, because of the time required to heat the pipes and adjust the temperature.
I installed a Wolter flash heater on our last cat, but concerned about using too much water, I plumbed a recirculating line that fed right back to the Wolter intake connection. I would hold the hot water line at the shower, and when it became warm, I'd close the recirculating valve.

Imperative not to leave the valve open as the temp would climb and climb and damage to the heater could occur.
 
#26 ·
In Hal Roth's book "How to Sail Around the World" he says that his wife and himself simple used a pump sprayer he modified with a nozzle from a kitchen sink. They would just boil a certain amount of water and pour it into the sprayer with some cool water. Then they would just pump up the sprayer with some pressure and shower. This way they were able to take hot showers and conserve water. I thought the book was great. It is just packed with information like that.
 
#33 ·
I used one of those for many years. I found it preferable to solar cos you can control the heat but thats about all.

On Raven, our previous boat, I went one step further, mixing the hot/cold in a bucket or head basin then dropping one of those cheap 12v shower gizmos you can but at any chandlery. We could use either kettle or solar to heat the water. Worked well and with some simple plumbing you could make it a more permanent installation.

That said, I love our tank heater shower on the current Womboat. Sheer bliss, other than (as per previous quite) having to run the engine to heat the water.
 
#27 ·
Pump sprayer is possible, but clearly it is more like camping than living in a waterside condo, as you put it. Depends on your requirements. We've decided to outfit our boat like it was our second home. Because it is. Electric tank water heater is always hot at the dock (unless we are away), air conditioning and heat pump, genset for when at anchor, etc.
 
#29 ·
We have a Raritan 6 gallon marine (120V and engine). As liveaboards we found it inadequate for more than 2 showers in a row. We just installed a Wabasto diesel hydronic heating system and looped it through the Raritan. We now have "unlimited" hot water dependent only on the water left in the holding tanks. The water maker takes care of the water issues.
 
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