Water tanks

[Navatech]

OK, the old tanks are shot and need replacing. Yes, I could have the old one's repaired (cut out the rotten parts and weld in replacement pieces) but I don't like that idea. Especially as stainless steel changes properties along the welding lines.

So, my options are as follows:

1) Copies of the original tanks in stainless steel.
2) Standard plastic tanks.
3) Custom made plastic tanks (with the same measurements as the originals).

Option 1 is a viable option but the price is more expensive then options 2 & 3. Plus there's all kinds of issues with stainless steel tanks (e.g. crevice corrosion, weld corrosion etc). Option 2 is not a viable option due to the non rectangular shape of the old tanks. If I go that way I will have to give up about 40% of the previously available tankage. Option 3 is the one I'm currently favoring.

The makers specify 3/8" Polypropylene, baffled to U.S.C.G. Regulations and includes NPT standard fittings. My problem is that I have no experience with tanks that are fabricated from this material in this manner. If they had been molded I would go for them in a heartbeat. But they're not molded but rather fabricated (out of sheet material that is "welded" together).

Any opinions and/or personal experience with this sort tanks?!...

P.S. I´m going to use the tanks for drinking water. This boat will, on occasion, be more then 24 hours away from shore.
P.P.S. This is about the two water tanks that are under the cockpit deck. The one in the ER is fine!

[Tony Meola]

http://www.ronco-plastics.com/newRonco/ ... hp?catID=1" onclick="window.open(this.href);return false;

Take a look at these. They are roto molded. They used to make custom sizes not sure if they still do.

[Rocket]

We use plastic welding to repair recycling bins made out of injection molded high density polyethylene ( #2 HDPE plastic) The welds are beautiful and are as strong or stronger than the surrounding material . Polypropylene is similair stuff, although more brittle (#5 PP Plastic, same as is used the tubs in yoghurt containers, the lids are HDPE because they need to be more flexible) If it is the same process, I would have no hesitation in using it for a water tank.

[Todd Pearce]

not sure if its possible but have you thought of installing a bladder in to the old tanks??

[Navatech]

Take a look at these. They are roto molded. They used to make custom sizes not sure if they still do.

I had already checked out those guys. They don't do custom sizes anymore :-(

[Navatech]

We use plastic welding to repair recycling bins made out of injection molded high density polyethylene ( #2 HDPE plastic) The welds are beautiful and are as strong or stronger than the surrounding material . Polypropylene is similair stuff, although more brittle (#5 PP Plastic, same as is used the tubs in yoghurt containers, the lids are HDPE because they need to be more flexible) If it is the same process, I would have no hesitation in using it for a water tank.

This is a link to their web site: http://www.plasticfabricatedtanks.com/boat.html.

I like the fact that they pressure test their product to double the requirement.

[Navatech]

not sure if its possible but have you thought of installing a bladder in to the old tanks??

Yes, I considered that option but it's not viable for the same reason that option #2 isn't viable. The form factor (vertical lip on the bottom) of the original isn't conductive to this solution. The bladder WILL move and then there will be accelerated wear of the bladder.

[Todd Pearce]

Hi, I have a friend down here who makes custom tanks for chemical company`s to very high standards,out of sheet welded together,and they have never had one fail on a weld,and the stuff they build for is nasty, to me ,I`d go with the welded sheet option

[Peter]

A question:

One reason to avoid plastic fuel tanks under decks with the new E-10 was that the ethanol will permeate through the plastic leading to oders in the bilge.

This is relevant to your water tanks if you will be winterizing them with anti-freeze. Not the oder, per say, but will the water still be tastless after the tank has steeped in anti freeze for a couple of months over the winter? Or will the plastic pick up some of the antifreeze oder and taste and leach it back out into the potable water all season long?

Someone once said to me "The first Christians got the best lions" which was his way of warning me about being the first to try out relativley untested technology in critical situations.

Frankly the welding process for stainless steel is pretty good these days. It is no longer the "heli-arc" stuff of 1960's legand when welding stainless was considered a bit exotic... and when CG regfulations were written about SST fuel tanks. Nowadays any decent shop has a TIG welder and will make the welds beutifully. As for corrosion from fresh water, it would be minimal. But of course that is also true for aluminum, which would be far less expensive, and in fact easier to weld reliably.

Lastly, the water is already inside your hull to begin with. So what is the big worry if a weld fails and the water leaks out of the tank into the bilge? Its not like gasoline which would be a huge hazard. And it is not like it is going ot sink the boat, because it is already in the boat.

I am pleased to see the possibility of getting welded custom plastic tanks, but for my 2 cents I'd stick with the tried and true. Another thirty years on new aluminum tanks and by then it will probably be among the least of the projects to fix on the boat. And if you go stainless it will probably take 50 years before they are a worry.

Peter

[John F.]

A question:

One reason to avoid plastic fuel tanks under decks with the new E-10 was that the ethanol will permeate through the plastic leading to oders in the bilge.

This is relevant to your water tanks if you will be winterizing them with anti-freeze. Not the oder, per say, but will the water still be tastless after the tank has steeped in anti freeze for a couple of months over the winter? Or will the plastic pick up some of the antifreeze oder and taste and leach it back out into the potable water all season long?

Someone once said to me "The first Christians got the best lions" which was his way of warning me about being the first to try out relativley untested technology in critical situations.


Peter

To winterize, pump your tanks out and use the cheapest Vodka you can find to winterize. Works fine. I never used anti-freeze in any water system I was going to drink out of.

[PeterPalmieri]

Peter,

Very well thought out response. I'd think much more simply, if the tank needs to be replaced buy an off the shelf plastic tank and don't drink the water. No need to worry about ingesting the antifreeze either.. I don't care if the tank is made of glass if it's sitting for any length of time especially in the summer it's not gonna be good.

Pete

[Rocket]

To winterize, pump your tanks out and use the cheapest Vodka you can find to winterize. Works fine. I never used anti-freeze in any water system I was going to drink out of.

No wonder that first cruise of the year is so much fun...

[bbtiller]

I just bought two of these, they fit with room to spare under the cabin deck. Allows room for fittings on top for fill and vent and on ends at bottom for feed to supply freshwater as needed. 44 gals total should be adequate.

http://www.tank-depot.com/productdetail ... rt=RW-B134" onclick="window.open(this.href);return false;

[Tony Meola]

I just bought two of these, they fit with room to spare under the cabin deck. Allows room for fittings on top for fill and vent and on ends at bottom for feed to supply freshwater as needed. 44 gals total should be adequate.

http://www.tank-depot.com/productdetail ... rt=RW-B134" onclick="window.open(this.href);return false;

Hey that is a Ronco tank.

[Navatech]

Winterizing is not an issue in SEF (South East Florida). Yes, I avoid cold weather like the plague :-)

The old Stainless Steel tanks didn't last 30 years...

And no, "welding" Polypropylene isn't an exotic or new fangled technology. My concern is that I was wondering how it held up in a marine (non-static) environment where the liquid sloshing around would exert additional loads. Even with the baffles in the tank.

The current tanks are 48 gallons each and I really don't want to give up the convenience of having ample water. More often then not there will be at least 6 people on board...

[Peter]

Navatech;

FIrst let me begin by saying I am not trying to rain on your parade. My input is meant only to be another perspective on the choice. I fully respect whatever choice you make....and frankly I'd love to see how the polypro tanks would work out, but forgive me if I say I'd like to find out on on someone else's dime. Maybe you agree with me about that, maybe you don't. But that is your choice to make, not mine.


First:
Wait a minute....

Your stainless steel tanks didn't last 30 years? That begs the question, assuming you are only used them for potable water, as to what sort of stainless they were made from?

Not all stainless is equal, It isn't called "Stain FREE. It is called stain LESS because it WILL rust and stain,.... just less so than mild steel. Some grades rust more than others.

For instance the stuff used for your kitchen knives is 440 and it will rust, but is specified for knives because it takes a better edge. The very best knives are not stainless at all and cannot be left wet on the counter for even several minutes without turning black, much less put through the diswasher; so the 440 SST suits the average home ower's balance of need between dishwasher safe and holding a good edge. But it would suck for fittings or tanks on a boat.It would rust away in a matter of years in a marine environment, particualrly in the lighter gages.

Other rusting stainless grades are used where magnetic properties are important. Macining properties differ and also welding properties differ between the grades. If you want to get a rough idea if you have "rusting" stainess or not see if a kitchen magnet sticks to it. For marine grade stainless the magnet won't stick at all. But in the kitchen grade stainless the magnet usually sticks anywhere from from barely to pretty strongly.

Anyplace in amarine environment you should at minimum use a 316 or a 316L which is a very rust resistant grade of stainless. One suitable for long term use in salt water and marine environments. Nowadays all the better fabricators know how to macine and weld it properly. But of course it costs more than a 440 grade. So if you just say "Make me a stainless steel tank" to a fab house the chances are you are going to get 440 or some variant thereof, not 316.

There are also more exotic grades of stainless even more corrosion resistant, but even more expensive.

As for winterizing; as long as the boat will never go north who cares? Until you want to sell it to someone up north.... Hmmm....

Welding of polypro might not be exotic, but I do not know how welded polypro works as a water tank in a boat. I think that was the point of your original post, i.e. asking if anyone knew anything about this particular application or had first hand experience.

The fact that there seems to be limited to no experience in this application means you are going to be the first to experiment with it if you decide to go that route. Are you prepared to risk the unforseen consequences? It is not just about material strength. It is about other factors from anti freeze compatibility, to vibration, to exposure to bilge fumes, to repeated G loading when in a pounding sea, to mounting questions, to longevity, to resale value, impact resistance, and so on and so forth. And those are the ones I can think of. It is the ones that no one has thought of yet that will bite you the hardest.

In light of these questions what are the specific upsides that you hope to gain by using the welded polypro tanks? What specific properties of the polypro lead you to expect these improvements over the currently used technology? What is your plan if it goes badly? How difficult/ expensive/ inconvenient is it to re-do the project? If you have to undergo a major re-do, is it worth it? What about 1 year in? How about 5 years in? Or 15?

I'm not asking that you answer any of those questions here unless you want to; I'm just saying that this is a way to evaluate your choice.

I am going to be very careful to repeat that I am not trying to critique your choice, whatever it might be. Trust me, I have done enough "from-scratch" designs to know that everyone has a criticism after the design is done, but none of them were helpful when there was only a clean sheet of paper.... and listening to thier reasons why it shouldn't have been done, or how it could have been done better after the fact is not appreciated.

So I am just offering you another way to look at the problem before you make your final decision. Take it for what it is worth.

I wish you the best of luck with whatever you choose. Keep us posted!

Peter

[lobsta1]

When I was hauled out this winter, there was a 42' downeast boat next to me. The new owner had the original builder come to the boat yard to do some work for him. I was talking to the builder & he said many of the downeast builders are using welded plastic tanks for diesel. These are 200 > 300 gal. tanks. I asked about the baffles. He said they were welded in & they had a zero failure rate on them. So I would guess that a couple of 48 gal tanks should be fine.

In my own boat I have waste & water tanks from Ronco plastics. They are 30 & 55 gal. tanks & are fine. Ronco does not make any tanks less than 3/8". Other manufacturers like Todd use a lot of 1/4".
Al

[Marlin]

The captain made mine,70 plus gal, fresh water head,lots of water usage especially in the Bahamas

[Navatech]

Well, I just got the new tanks and they look really good! Sturdy and durable. No smells to be noticed. I'll update as they are installed and used.

So far I think this was a good choice.















I'm very impressed with the results so far...

[Pete Fallon]

Elizier,
I was going to suggest the poly tanks I have had them in my 31 for 35 years with no problems, 25 gallon rectangular tank under the cabin sole in my boat. Now that you have them I feel that you made the right choice and you don't have to worry about winterizing them in PR. Have you had any luck with finding a base plate for the chair?
Pete Fallon

[Tony Meola]

Who did you finally use to make them up for you?

[Navatech]

I was going to suggest the poly tanks I have had them in my 31 for 35 years with no problems, 25 gallon rectangular tank under the cabin sole in my boat. Now that you have them I feel that you made the right choice and you don't have to worry about winterizing them in PR.

I (obviously) also believe I made the right choice. The boat isn't going to remain there (PR) but winterizing isn't a problem in SEF either :-)

Have you had any luck with finding a base plate for the chair?

Nothing yet but I haven't put too much effort into it. Been busy with other things.

[Navatech]

Who did you finally use to make them up for you?

Same guy in the link above. Ended up going for the thicker material. Turns out he's about an hour north of me on I-95 so I went to pick them up myself. Was there for the pressure testing :-)

The guy is originally from South Africa and has been in business for several years now. Most of his work is OEM for manufacturers. He's booked up 4-6 weeks in advance. I felt (and continue to feel) good about the whole thing.

Of course, the actual proof of the pudding is in the taste (no pun intended) and I will report back on that.

[PeterPalmieri]

What's the concensus on Potable water? I do not drink the water in my tank, besides provisions for my intended trip I keep a couple cases of bottled water or gallon jugs on the boat. I realize you guys running to the Bahamas or other places have more logistical concerns.

Water in my tank can be laying around for a while, what's the shelf life in a tank on board and are you treating the water?

Do sinks drain to the same holding tank as the toilet? Pump out station isn't my favorite place, so I tend to limit usage

[CaptPatrick]

Do sinks drain to the same holding tank as the toilet?

Sinks usually drain directly overboard. The drain should still have a goose neck to prevent diamond rings from loss or insects from entering if the drain is above the waterline.

[IRGuy]

On my boat the sinks ("grey water") drain directly overboard.. only the head ("black water") drains to the waste holding tank, on which I have a deck pumpout fitting and a diaphragm pump for overboard discharge when at sea.

Lots of excellent info above! I am getting ready to install a complete fresh water system on my B33.. the previous water tank was removed by the PO when it started to leak, but never replaced, and the piping he installed is a mess, so everything will be replaced. I plan on using a ready made tank from Ronco.. have done some business with them before and liked their service.

As an aside.. I did a lot of offshore sailing on a 36' sailboat.. the boat had a flexible bladder fresh water tank, which had been in service for about 8 years, It started to leak midway between Boston and Bermuda, so we saved as much of the water as we could and dumped the rest. When we got to BDA we removed the bladder, which was semi-transparent. The inside surfaces seemed to have a brownish coloration, so we cut the tank open.. the inner surfaces were completely coated with a brown slime that smelled bad.. up to that point we drank the water from the tank.. now I always bring bottled water from home.. either store bought bottles or tap water from my house in empty gallon milk jugs, reserved for drinking. Tank water is used for washing and rinsing, but we don't drink it any longer. The good thing about plastic bottles and jugs is that you can store them in small odd shaped spaces which otherwise might be wasted.

[Navatech]

What's the concensus on Potable water? I do not drink the water in my tank, besides provisions for my intended trip I keep a couple cases of bottled water or gallon jugs on the boat. I realize you guys running to the Bahamas or other places have more logistical concerns.

Water in my tank can be laying around for a while, what's the shelf life in a tank on board and are you treating the water?

Potable water on a boat has several uses: hygienic usage (showering etc), cooking, drinking. obviously external usage (e.g. shower) doesn't require the water to be as "good" as internal usage (teeth brushing, drinking etc)... Cooking is an internal use but the water does get boiled pror to ingesting the result so aside from possible bad taste you're mostly going to be OK...

Back when I was in the (Israeli) navy we had a complement of 40-50 guys and 2 tanks of 6,000 liter (1,500 gallon) each onboard... Obviously, that's not enough for longer travel... So we had water makers that ran of the waste heat of the main engines... Basically, seawater was boiled (in a vacuum to lower the boiling point) by the cooling water exiting the engines... When we ran those the water tanks were set up to operate individually (commonly they were interconnected) and ALL the newly made potable water was directed into one of the two... That way a faulty water maker wouldn't contaminate ALL the water onboard...

As far as shelf life of water goes, the more you use it the better... Sealed (bottled or canned) water being the exception... Usage keeps the water useable... When you put the boat away for a while you should FILL the tank(s) completely as the air/water interface would be a source of contamination... I would dump all the existing water when I came back, fill the tank and add some disinfectant (e.g. bleach, chlorine, bromide, baking soda)... After letting the disinfectant work I'd dump the water and then refill with a fresh batch... Depending on the disinfectant you used you might have to repeat this... In any case, a sediment (particle) and taste (charcoal) filter after the tanks would be a good idea...

If you only go on day trips sealed jugs of water to be used for internal purposes might be the best idea... However, for multiple day trips that's not really practical (assuming there's more then 1-2 persons onboard)...

Do sinks drain to the same holding tank as the toilet? Pump out station isn't my favorite place, so I tend to limit usage

The law requires only that "black" water be directed to the holding tank... I.e. "gray" water is exempted and may be discharged most anywhere... This may be different in areas other then the US where there are different laws...