Crazy thought for fresh water tank

[SS MAYFLOAT]

Just had one of those sit, stare and think awhile moments. On my cabin cruiser, I have 2 storage tanks for my potable water. Each are 17 gallons. Each one is located in each corner of the rear of the boat. They sit just above the water line as well. Presently both tanks stink and I won't even let the dog drink water from them. <br /><br />Right now I'm in some restoration. I have removed the flooring on the outter section of the first stringer.

<br />This cavity from front to rear is 16' long. Each side is the same. So here is what I'm thinking,,,, There is enough room to put 2 pcs of 4"pvc pipe 15' long. I could do this on each side for the total of 60'. Of course I would cap the ends, and do all the neccessay hardware to use them as my storage tanks. Accoring to my calculations, this will give me about 40 gallons. Presently I have 34.<br /><br />After they would be installed, I would then pour my floatation foam in and around them. I think it would spread my load out more evenly, reduce weight on the stern, and lower my center of gravity. With the bridge and several overgrown adults, the boat gets a bit tippy in rough water.<br />Plus, I don't think the PVC will end up stinking like the tanks end up doing.<br /><br />Whats your opinion? crazy or maybe a logical idea?

 

[JB]

Re: Crazy thought for fresh water tank

Maybe logical.

 

[eeboater]

Re: Crazy thought for fresh water tank

That actually sounds like a pretty good idea SS. As long as the water sitting in the PVC cannot spoil, I think you'd be good. I'd also make absolutely sure that the connectors between the PVC tubes are sealed tight... that would suck to have a leak into the stringers from your freshwater tank.

 

[tashasdaddy]

Re: Crazy thought for fresh water tank

i believe it could work very well, i think i would want some type of circulating pump to move the water thru all the tubes, so you don't have stagnate water. this could be done if you are using and water pump, just put a stop **** in it the direct the water to circulate, or turn the stop **** to supply the sink, etc.

 

[JB]

Re: Crazy thought for fresh water tank

Just thought of this. <br /><br />Weight distribution would be fine at rest, but what happens to the water when they are partially full and you start out of the hole? Sudden shift of weight to the stern might not be good for handling.

 

[Bondo]

Re: Crazy thought for fresh water tank

I think it's a Brilliant Idea...........<br /><br />Make Sure you add Drains to them........<br />That way you can Drain,+ Replace with Fresh Water,... As well as Drain for Winter Storage......

 

[SS MAYFLOAT]

Re: Crazy thought for fresh water tank

Fully loaded the boat will weigh in at 8400 to 8600 pounds. Sad thing is with this model of boat, they have been known to be underpowered. Ask SoLittle, he had one of these Victoria Snails also. A fast hole shot with this boat is something it will never see unless I repower it with a big block. With 2 people on board, 1/2 tank of fuel, and NO gear,,,,,,,this boat may get up on plane in about a quarter of a mile or so at WOT. Throttle back a little bit, and it will come off its plane quicker than it took to get her there.<br /><br />With that said, shifting of weight will be not near as noticable as before with the original tanks. Water slopped around in them quiet a bit also. <br /><br />Concerns on water becoming stagnant. When the boat is in the water for the season, that is the only time that water will be stored in them. With the constant wave action of other boaters, I don't think the water is ever going to have a chance to settle down unless it is during night time. Another ingredient that aids in sour water is the rise in temp. The present location, the heat from outside, and engine will warm the storage water where it is now located. If they are located next to the hull, the lake water will keep them cooler since they will be next to the bottom of the boat.<br /><br />Another bonus to this idea is the new aquired storage space from the old tanks. There would be room to install a future generator.<br /><br />I'm not completely sold on this idea and still looking for more options. It does look tempting to go ahead........ Thanks......SS

 

[SS MAYFLOAT]

Re: Crazy thought for fresh water tank

Thanks Bondo, you must have posted while I was typing the last post.<br /><br />I know I need to have offset caps to allow the water to be drained at the lowest points of the pipe. Also I will need to put air bleed valves to equalize the air pressure in them during use and filling. On the air bleed, I will use a filter. That way all air going in or out of the tank will be filtered to keep out contaminants. Especially those pesky dock spiders <br /><br />I won't have much room for having a drop to pitch them downward. My calculations is that I can have about 1/8" of drop for every foot. That gives me about 2" for the 15' length. This will help utilize all the water in the tanks and prevent my pump from cavitation. <br /><br />Hmmmmm, sounds better and better the more I think about it. Sad thing is, the thinking takes longer than the actual work.

 

[tommays]

Re: Crazy thought for fresh water tank

My only thought would be to use # 80 PVC we have a lot of problems with the 40 stress cracking <br /><br /><br />tommays

 

[SS MAYFLOAT]

Re: Crazy thought for fresh water tank

Thanks Tom, The stress cracking your talking about, is it due to them being pressurized with the water pressure? These wouldn't be under any pressure, would that still cause stress problems? The pipes will be encased with foam and will offer support of them. Actually, you maybe right. With them being ridgidly fastened/encased into the floatation chamber, they would act as a structural support.<br /><br />What is the weight difference between schedule 40 and 80?

 

[tommays]

Re: Crazy thought for fresh water tank

# 80 has about doubble the wall thickness <br /><br />We use a lot of PVC in are chilled water and are PURE water systems<br /> <br />#40 = even regular valve turning causes cracks<br /><br />#80 = put it once and pretty much never worry about except that time the delivery tanker hit he water chiller and moved it 3' off its pad<br /><br /><br />tommays

 

[studlymandingo]

Re: Crazy thought for fresh water tank

SS, I have a 29' SportCraft (don't use it much because of the 454 Mercruiser that drinks 28 GPH). The PVC pipe for Freshwater is exactly what is used on this boat. The guy I got the boat from redid the stringers 10 years ago, and that is the way he did the freshwater system. Works great, and I don't really notice the weight shift when taking off.

 

[mattttt25]

Re: Crazy thought for fresh water tank

only question i'd have is will the pipes be level when the boat is at rest? and where will your pickup be? want to make sure you can actually get the water out of the pipes.

 

[SS MAYFLOAT]

Re: Crazy thought for fresh water tank

Matt,lucky I still have a bit of a water line marking on the antifoul paint. I've jacked and blocked the boat so that the water line is level.<br />For the whole 15' length, I'll have a 2" drop. That should be plenty to get it to drain. Might be a problem if I'm going down hill, but I don't think I'll be driving my boat in hilly country.<br /><br />Was also thinking that I could also use them as a ballast tank system when sitting and fishing. If I have a couple of heavy weights onboard, I could move water from one side to the other to level the boat out. Of course that is going to be more $$ for pumps & switches. I'll put that idea on the back burnner for now. I gotta get this back together before winter comes back.

 

[Silvertip]

Re: Crazy thought for fresh water tank

Regardless what type of storage method is used for fresh water, the system needs to be sanitized regularly or you will still have skunky water.

 

[blouderback]

Re: Crazy thought for fresh water tank

Check your math. Volume of a cylinder is:<br /><br /> Pi * R Squared * length<br /><br />The radius of a 4" PVC pipe is 2", so <br />that's 3.14 * (2 squared) * 180 inches = 2,260 cubic inches.<br /><br />There are 231 cubic inches per gallon, so 2,260 divided by 231 = 9.7 gallons. If you do 2 of these PVC pipes, that's less than 20 gallons.<br /><br />Did I do the math right?

 

[blouderback]

Re: Crazy thought for fresh water tank

Nevermind, I just saw that you are doing TWO per side. You're right, that gives you just about 40 gallons.

 

[SS MAYFLOAT]

Re: Crazy thought for fresh water tank

Thanks Bob, I just asked Jeeves and it put up all the different conversions to figure it out. Just put in my measurements, clicked and got the results. I drove my wife nuts trying to get her to figure it out. Sad part is, she just finished her algebra courses about 6 months ago! <br /><br />Thanks for double checking for me, it is appreaciated very much!

 

[flashback]

Re: Crazy thought for fresh water tank

Is the glue for the end caps safe?

 

[SS MAYFLOAT]

Re: Crazy thought for fresh water tank

Flashback, Yeah, it should be, I'll be using what is normally used to glue it together, PVC cement. Its used in residential and commercial applications for water supplies. The PVC I have has the NSF (National Sanitation Foundation) which is recognized by health departments.<br /><br />I'll get some pics here fairly soon when ever the weather breaks from rain. Its been 6 days now. Quack quack..........SS