Water System Design Musings

[micah719]

My boat is still in the concept/design phase, a 46ft steel double ender long keel for shorthanding but with capacity for more. One of the current areas of focus is the fresh water system. Forgive me if I betray my noobishness with regard to plumbing. I'm filter-feeding as much info as I can, so I'm happy and grateful for any input. You can even abuse and revile me, it's all part of the learning process.

I won't have the power budget to run a watermaker, so I'll be limited to topping up from rain, solar still and canning it on via dinghy. Very unlikely I'll be docking often, if at all. Money-leeches lurk at docks, and anything with "marine" or "yacht" on it seems to have an automatic markup; makes life hard for people with boats. To avoid living hand-to-mouth and hard rationing I was thinking about some substantial water storage as a buffer to tide me over between fills. The solar still thing is further down the list, but I'll get there sometime. Got to have a bucket before you can fill it...

My guesstimate of potable water on this particular 46ft boat would be around 800L, split up into various tanks; figuring at having 8 x 100L for storage, a holding tank for incoming water before it gets final approval for use, and a gravity/demand tank. I don't expect to need so much water, but having it split up and isolated and having so much tankage would give a comfortable safety margin and watertight compartments. It's not like they'd all be filled to the brim, though one would try and keep it topped up whenever possible. If my planning changes as to the amount, then it would still be split into multiple separate tanks. I'd rather have too much than too little.

One area I'm totally uncertain of is the internal coating of the tanks. Have to research that a bit more before I plague folks with noob questions. For now, I'm thinking of the handling side of things.

To prevent cross contamination I'd like to have a central manifold and pump/s, so I can totally isolate any tank at will, preventing contamination of the whole supply from bugs in the system or a dodgy fill. The manifold itself would need flushing the most, and the outlet end of the system, and I was thinking about flexible hoses using compressed air fittings to completely isolate tanks when needed. The CA fittings I think would be good for longevity and integrity, particularly if they get a bit of use. Each tank would have a wide inspection port, drain cock, and ball valve on the outlet, with the CA fitting after that to plug into the manifold. I'd want electric and manual pumps, hooked up so I can pump both ways in any line.

I'm curious about the possibility of fitting a water-head pressure pipe up inside the mainmast, would this make for a simpler system and perhaps more consistent/higher pressure in the house system than a pressure bladder in a tank, or on-demand pumping? Would I need a water hammer preventer? Can rum be kept in a water tank? Ooops, did I type that or just think it....

[GordMay]

Rum should always be kept out in the open, for quick & easy access.

[Gabrieln]

Do you know PEX plumbing sistems?

[Stu Jackson]

Had a friend who went to Mexico, with a watermaker. He wrote: The watermaker was a great investment. I've seen the other side - people buying their water in 5 gallon jugs and trying to sneak in a little shampoo as they steal a beachside shower from a resort. It doesn't look like fun. We love the watermaker.
Capacity is important. The cheaper low volume Katadyne units have to run forever to make enough water. Something in the 150 gpd range is much better. We have a Spectra unit.

You might want to get a 2 foot shorter boat and get a watermaker.

[Pauls]

Hi Micah,
I am building a boat similar to yours, a 42' steel double ended cutter.

In my opinion you are getting way too complicated. Having 8 seperate tanks creates a complicated mess of fill and supply lines, manifolds, valves for isolation and supply, etc. It is a general design truth that simpler is better, and on a boat for long term sailing I think simplicity is a great virtue.

One of the great advantages of steel construction is that tanks can be built integrally with the hull. This is very efficient construction, as the hull forms one or more sides of the tank. The tanks strengthen the hull and form a double bottom, increasing the ability to take damage without sinking. This also gets the water weight as low in the hull as possible.

You for sure want 2 tanks, so that accidents happening to one will not ruin all your water. I'd suggest you consider 2 as being adequate. If you want more, bear in mind the added complications and find a balance that suits you.

Water tanks in steel are blasted after welding and then painted with an epoxy paint made for potable water tanks. Many city water supplies use steel tanks painted this way, some of them are 100 years old now. The old tech approach was/is to coat them with a thin coating of cement. This works very well. It needs to be redone every few years but is very cheap and easy.

If you have a filter in the tank fill line it can prevent sediment, etc from entering the tanks.

I don't understand your idea about compressed air in this system. Again, simplicity is a virtue. Commercially available (not marine) PVC ball valves are cheap, effective, and durable. I'd try to avoid marine store supplied anything unless it is absolutely unavailable anywhere else. Industrial supply parts will typically be better quality, more robust, and a fraction of the price.

Regards, Paul

[micah719]

Capt. May:
Rum should always be kept out in the open, for quick & easy access.

Aye aye sir! Thirst, the sailor's bane...(shudders with horror and reaches to cuddle the rationed Havana Club, and dreams of the Carribean)

Garbrieln:
Do you know PEX plumbing sistems?

Haven't used them, being a plumbing noob, but seen them on boatish blogs and they look a brilliant idea. Not a fan of anything plastic, but this may change if the facts overwhelm the prejudice.

Stu Jackson:
Capacity is important. The cheaper low volume Katadyne units have to run forever to make enough water. Something in the 150 gpd range is much better. We have a Spectra unit.

You might want to get a 2 foot shorter boat and get a watermaker.

The snag I see is the electric power, and the expense and availability of parts. The reason I want the option of a generous store of water is to try and buffer any holdups in the supply. Also, I would have the pleasure of being able to help out cruisers low on water and far from easy sources of clean water. The length question isn't fully settled yet and quite possibly would go down, after I nut out all the definite requirements and can start squeezing dimensions down; and I was dreaming of electric drive for maneuvering in tight spots, so a decent battery bank and charging setup is on the cards in the future anyway...so the watermaker might be an option sometime after all.

Pauls:
....
Having 8 seperate tanks creates a complicated mess of fill and supply lines, manifolds, valves for isolation and supply, etc. It is a general design truth that simpler is better, and on a boat for long term sailing I think simplicity is a great virtue.....

I hear you loud and clear and agree. The bulk of the water tankage would be either side of the keel with a sump and access space between. Breaking that up into multiple compartments gives me the double bottom and the ability to transfer for trim and maintenance, in addition to all the other benefits. Pre-construction is the time to work all this out, the thought of ripping my beloved sealady to bits and welding again after she is launched makes me queasy. With a bit of careful design I could avoid too many pipes and valves and connections.

Pauls:
I don't understand your idea about compressed air in this system. Again, simplicity is a virtue. Commercially available (not marine) PVC ball valves are cheap, effective, and durable. I'd try to avoid marine store supplied anything unless it is absolutely unavailable anywhere else. Industrial supply parts will typically be better quality, more robust, and a fraction of the price.

The main benefit of the CA fittings in my thinking is the ability to quickly and reliably chop and change the routing, and simplify access to all the parts of the system for cleaning and maintenance or replacement and still keep the setup running. I suppose the ability to easily hook up the compressor to the system would be useful for flushing it out or another method of pumping, or in damage control. Also, I was toying with the idea of a water filtering system using a charge of aggregate of varying sizes, which would need periodic backwash and airing....having pre-cleaned seawater was my idea of avoiding harbourwater stinking up the head or coming out of the shower/handbasins. Maybe it's not feasible, but that's the purpose of asking and ferreting for info. I hear you on the marine markup and simplicity issues...I am a notorious scrounger, hoarder and miser, not to mention being lazy, so whatever setup gets the construction approval is going to need to be cheap, simple and idiot-proof, and as versatile as possible.

Pauls:
.....I am building a boat similar to yours, a 42' steel double ended cutter......

Great news, and would love to hear more about her!

Still wondering about the gravity-pipe up the mast for a method for pressurising the demand system simply. Useable height would be in the range of 50 feet, which would give up to about a couple of atmospheres of pressure-head on tap. With clever connections this wouldn't need to be re-pumped up all that often, and seeing the masts are going to be steel and have a built in internal channel for wiring to the masthead, stuffing a water pipe up there is not impossible. Not for having hollywood showers all the time, but to avoid having to use a pump each and every time I want some water.

Thanks for the input, shipmates! A tot of grog for all hands!

[Tellie]

Still wondering about the gravity-pipe up the mast for a method for pressurising the demand system simply. Useable height would be in the range of 50 feet, which would give up to about a couple of atmospheres of pressure-head on tap. With clever connections this wouldn't need to be re-pumped up all that often, and seeing the masts are going to be steel and have a built in internal channel for wiring to the masthead, stuffing a water pipe up there is not impossible. Not for having hollywood showers all the time, but to avoid having to use a pump each and every time I want some water.

Thanks for the input, shipmates! A tot of grog for all hands![/QUOTE]



I don't get it. If you're going to have a pump on board to fill the mast for head pressure then you have a pump on board for head pressure without the mast. Don't over complicate this water system.


"The reason I want the option of a generous store of water is to try and buffer any holdups in the supply. Also, I would have the pleasure of being able to help out cruisers low on water and far from easy sources of clean water."


OK, this one gave me the Tellie giggles. Your generosity is admirable but...First, by the time you get to the areas far from easy sources of clean water you're not going to have 211 gallons of water left in your tanks. Second, what's left in your tanks in areas far from cleam water sources is NOT something you'll be giving away to anyone except in dire emergencies Grasshopper.

[Stumble]

Your idea is vastly overcomplicated... There are a couple of issues as I see it in your proposal.

1) Multiple tanks are a great idea, but the more tanks, the more fittings, the more deck plates, ect. All of these take time and effort to maintain, and to regularly inspect. How much time, well that is a function of how hard they are to get too, and how many of them there are. On a boat your size two would be typical, either a port and starboard, or a forward and aft. Possibly with a third placed on centerline somewhere.

If you want a filtering system (which I would highly recommend for potable water) then the three tanks join a manifold, and the manifold feeds the filter. This way all potable water gets filtered, and plumbing is kept to a minimum.

2) sending water up the mast is frankly just silly. If you were to say use a 2" pipe (necessary to have enough water to matter) with a 5 gallon tank at the top to provide pressurized water, at 50' off the deck...

You would have 8 gallons in the pipe. At a weight of 24lbs. The average height would be 25' off the deck, so this water would decrease righting moment of the boat by just shy of 600 foot lbs.

The 5 gallon tank at the top would reduce it a further 250 foot pounds.

Assuming you had a 6' deep fin keel, this would have the same effect on righting moment as 285lbs in the keel.

Assuming you use PVC schedule 40 pipe, it weighs in at .68lbs/foot, so you have another 34lbs at an average height of 25' so another 850 foot pounds... Which requires another 285lbs in the keel.

So whatever the weight of your keel, add an extra 570lbs just for your pressurized water system. Plus whatever the specs are for the delivery tubing.

3) I have never seen a compressed air system hooked up to water system, nor can I really imagine a need for one. Back flushing can be done with water, just add a tap at the manifold from the tanks.

4) without a water maker you will always have an issue with water availability, unless you are at the dock. Fresh, untreated water goes bad relatively quickly, giving away some of yours is likely to be a bad idea, unless you just filled up from a rain they missed.

5) it is always prefered to have a smaller number of full tanks than a large number of partially filled ones. For stability reasons half full tanks will drain to the low side of the tank, and exacerbate heel. This is referred to as 'pressing tanks' and should be done whenever possible.

If you do decide to add multiple tanks, consider adding two water tanks to the outboard edge at the widest point of the boat. This will allow you to use them for trimming and ballast tanks (only one should be full at a time). Similarly to a water ballast system. In a pinch you could drain them both into the main tanks, and use salt water to provide ballast.

Personally I think you have made this much more complicated than it really should be. A reasonably sized tank is a good thing, split into two mains and a third day tank, to hold water until it is approved for consumption. Is as complicated as I would consider, or want.

The only thing I might add is a water maker that can draw from the fresh water tanks to purify the water. In the event that I got a bad fill somewhere.

[micah719]

Tellie:
I don't get it. If you're going to have a pump on board to fill the mast for head pressure then you have a pump on board for head pressure without the mast. Don't over complicate this water system.

Ok, the brain fart in that direction is over....was already a bit leery of the weight so high and how to get it to work. Stumble's calcs helped though eventually I would have got there myself and frightened myself into dropping it. Trying to think outside the box, got a little too far off. No in-mast water pipe.

Tellie:
OK, this one gave me the Tellie giggles. Your generosity is admirable but...First, by the time you get to the areas far from easy sources of clean water you're not going to have 211 gallons of water left in your tanks. Second, what's left in your tanks in areas far from cleam water sources is NOT something you'll be giving away to anyone except in dire emergencies Grasshopper.

What's wrong with water you can chew?!? Ok, point taken. I'd still like the multiple redundancy of reserve tank space, though.

Stumble:
I have never seen a compressed air system hooked up to water system, nor can I really imagine a need for one. Back flushing can be done with water, just add a tap at the manifold from the tanks.

The main reason for CA fittings is that they're cheap, easily available, are airtight, robust and designed for a lot of use. The ability to hook up a compressor is merely a side-benefit, and seeing I'm brainstorming some outlandish stuff is to be expected. Having plumbing fittings that are semi-permanently sealed freezes the system in place, and having the "marine" pricetag doesn't mean it really is marine.

Stumble:
it is always prefered to have a smaller number of full tanks than a large number of partially filled ones.

Yes, the free surface effect does feature in my thoughts on the system...hence the multiple tanks, and narrow on the beam seeing as how it's unlikely I'll be pitchpoled by the sloshing in the tanks. A clever choice of tank sizes means I can reduce the amount of half-full ones.

Stumble:
The only thing I might add is a water maker that can draw from the fresh water tanks to purify the water. In the event that I got a bad fill somewhere.

The watermaker is on the cards, but I do not want to make it something I am overly relying on...the energy budget and spares being the main consideration. The use of the tanks for trim: I was intending to have the batteries on racks, securely bolted but with the ability to be shifted so all that lead can be used to get the trim reasonably level, and the tanks for easy and quick adjustment.


Summary: No mast pressure-head pipe, no free slime giveaway to dehydrated cruisers. Still no conclusive reason to drop the CA fittings.

Thanks for the input! Happy sails...

[Tellie]

I like outside the box thinking. Most of it does end up useless, but then there's that gem every now and then that moves mankind forward.

[bobconnie]

Thinking outside the box is great ! BUT I and others have found out that The KISS princple is still the best for boats !! If Connie did not insist on her showers, I would still have nothing but cold water and a hand pump for my on board water system LOL just my 2 cents

[Cruisingscotts]

Your concept is not new, the over engineered simplicity. If you are dead set on a no power fw system your best bet is to go in the way back machine and pic up some older 60s and 70s cruising how to books, don street matte etc. one of the most basic setups was a couple integral storage tanks and a warm day tank on deck painted black filled with a hand pump gravity fed. There is actually a lot of info out there on solar hot water boxes. You can make low tech burn yourself hot water boxes, A friend did one for his engineering thesis. We started with a bare hull and for fw and other things I took the boat telling you what to do approach. We have two small 35. Gal tanks in the otherwise unusable space under our outboard sette seats. These are not enough capacity for long term passages. After a few years of living on the boat as a family with guests etc we will have a good idea of how much more tankage we need weather we want a water maker etc. I have ample accessible bilge space for more tankage and all the thru hulls etc to put in the wm. If you layout your boat with this in mind it gives you lots of options.

[micah719]

Bob & Connie:
Thinking outside the box is great ! BUT I and others have found out that The KISS princple is still the best for boats !! If Connie did not insist on her showers, I would still have nothing but cold water and a hand pump for my on board water system LOL just my 2 cents

Yep, the less to go wrong is better. The more options one has when it does go wrong is also good. I can add all the comforts if life becomes unbearable....or, can be used as evidence of a deep and abiding love e.g. (look, darling! I love you so much I'm ripping the guts out of my, er, our boat and scorching up the paint to fit a lovely bathroom, just for you...cringe grovel please speak to me again).

Your concept is not new, the over engineered simplicity. If you are dead set on a no power fw system your best bet is to go in the way back machine and pic up some older 60s and 70s cruising how to books, don street matte etc. one of the most basic setups was a couple integral storage tanks and a warm day tank on deck painted black filled with a hand pump gravity fed. There is actually a lot of info out there on solar hot water boxes. You can make low tech burn yourself hot water boxes, A friend did one for his engineering thesis. We started with a bare hull and for fw and other things I took the boat telling you what to do approach. We have two small 35. Gal tanks in the otherwise unusable space under our outboard sette seats. These are not enough capacity for long term passages. After a few years of living on the boat as a family with guests etc we will have a good idea of how much more tankage we need weather we want a water maker etc. I have ample accessible bilge space for more tankage and all the thru hulls etc to put in the wm. If you layout your boat with this in mind it gives you lots of options.

The bit about the boat telling you what it wants appeals to me; hence all the thought-experiments so that whatever goes down on the "build!" plan is functional, robust, and leaves as many options as possible. For sure there will be alterations later, but I'd rather have already done them in the simulator and bounced them of the experienced folk first...probably less grief that way. Two wise folk on this thread have already done themselves out of a free gift of Micah's Vintage Pondscum....they'll have to make do with rum.

Btw, I was strongly considering having only one through-hull below the load waterline....the intake to the seachest. With a grey water holding tank and a brown water holding tank, both either pumped out at disposal points or dumped out where it won't dilute the pristine outflows of towns, I don't need a submerged outlet. Probably need to keep an eye on the above-water outlet to avoid unsightly stains, but one hole to watch is better than two. I like the idea of having it all as simple and robust as possible...I can always add holes later if really needed.

Is it possible to have a seawater holding tank and filter/treat it to prevent it stinkng up? That way I can even keep the intake thruhull closed when I'm not filling the SW tank.

[Cruisingscotts]

A seachest is standard on any vessel of size or ship. You have 2 thru hull valves going to strainers which connect to a common manifold. It does not make sense on a small vessel unless you are going to have all kinds of stuff coming off of it pumps gen etc. Discharging black water above the waterline, would certainly leave its mark. I'm a big fan of a gravity draining holding tank built in to a false bulkhead or such a very simple setup that is easy to flush out when outside of 3 miles. A grey water tank is a must on a new build as 100% no discharge zones will only be growing, plus it makes your plumbing much simpler and gives more flexibility on layout. The down side being you will have to empty the tank manually or electrically.

[micah719]

A seachest is standard on any vessel of size or ship. You have 2 thru hull valves going to strainers which connect to a common manifold. It does not make sense on a small vessel unless you are going to have all kinds of stuff coming off of it pumps gen etc. Discharging black water above the waterline, would certainly leave its mark.

Why two valves? I thought a standpipe and gooseneck with a vent would work.

Seawater requirements would be the head and sinks; and was considering having the electric and emergency diesel bilge pump set up with the option of a hose hookup to the deck: anchor muck washdown, seawater shower, dinghy rinse, etc

When pumping out, a brush on a stick and a good rinse right after should surely prevent any stains? The vent through-hull would be near the stern and on the lee side when discharging, so there is an overhang, not too much dribbling.

Also, I'm a bit leery of having that stuff anywhere other than as low as possible.

The down side being you will have to empty the tank manually or electrically.

Attention, crew to pumping stations! I'll supervise....and fiddle about with my handheld anemometer, so I'll have to go over here to the windward rail....