Poly vs stainless tanks ?

cameronsturgess

Active member
Any recommendations regarding fresh water tank ? Considering a 70 gal fresh water tank inside box over rear axle. Pros and cons of stainless or poly ? How to stop sloshing water ? Interior baffles or baffle balls ? Vendor suggestions ? Similar questions for grey tank to be mounted under truck between frame rails. Likely around 40 gal. Thanks. Cameron
 

Alloy

Well-known member
I can build stainless tanks but I paid someone to build my poly tanks.

Poly is lighter, cheaper and inert.
 
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SkiFreak

Crazy Person
Some say that plastic tanks do not taint the taste of water, but I am not of that opinion. I have stainless water tanks for that reason alone.
That said, stainless tanks are normally heavier and more expensive than plastic tanks and require fixation in an area that does not stress the welds. In a truck the baffles should run north/south.
My grey and black tanks are plastic.
 

luthj

Engineer In Residence
I have used a number of PP and PE tanks. All were food grade, and has zero taste after a few fills. If you are concerned, you can add an in-line carbon filter at the faucet. Stainless can sometimes interact with dissolved solids in water to make scale or rarely taste. It also needs to be designed to avoid all oil canning, or similar flexing, as it will work harden and stress crack. Roto molded, or even welded PP/PE tanks are not terribly expensive, and are 100% resistant to bleach. If you regularly use high dose chlorine/bleach to sterilize the tank (some folks pump surface water for showering), then you need to beware of stress corrosion cracking in stainless. The chlorine at higher levels causes the micro corrosion which can cause crack formation in some cases.
 

Howard70

Adventurer
If you go with poly tanks, consider a "welded" in metal insert threaded to accept your drain plug. It's pretty easy to foul threads in plastic materials if one even slightly over tightens a bung. If you have the space you could also consider a low profile valve for your drain plug and avoid thread problems all together. We've found we use the drain plug more than expected:

1. Removing all water from external tanks in winter.

2. Accessing water in the tank when some plumbing/pumping problem develops.

Howard
 

billiebob

Well-known member
Any recommendations regarding fresh water tank ? Considering a 70 gal fresh water tank inside box over rear axle. Pros and cons of stainless or poly ? How to stop sloshing water ? Interior baffles or baffle balls ? Vendor suggestions ? Similar questions for grey tank to be mounted under truck between frame rails. Likely around 40 gal. Thanks. Cameron
So you are adding 900#. How does that work with your GVWR ?
But to the question, I'd go with a "Potable Water Food Grade" poly tank.

Might depend on how far, often, remote you travel. Heading for 3 years in Africa or South America I would likely pick SS
 
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steve66

Observer
I went with 10mm HDPE welded tanks. I have 6 tanks of various shapes and sizes to make maximum use of the available space, about 600 lts of fresh and drinking all up plus a grey tank, no black. Didn't fit any baffles

The guy who made them gave me a lesson in how to repair a crack if ever needed but hopefully not.

Stainless was dearer plus was worried about corrosion.

I have one tank above the DPF so fitted a heat guard.
 

gait

Explorer
I made my own, welded from food grade PP. It was cost effective after 3 tanks. Cost of welders has fallen considerably since 10 years ago.
 

Peter_n_Margaret

Adventurer
I have 2 commercially sourced HDPE water tanks (70L each and 3mm wall thickness) plus 2 DIY rotationally moulded HDPE water tanks (55L each and 5mm wall thickness) plus 2 DIY rotationally moulded HDPE fuel tanks (80L each and 10mm wall thickness) plus one commercially made SS water tank (100L).
The SS tank fatigue cracks and I will replace it with another DIY rotationally moulded HDPE tank.
I use spin welded threaded fittings in the HDPE tanks. The DIY HDPE tanks have all been in use for 14 years.
Never had a taste issue and we regularly add chlorine as we fill.
I think the "sloshing" problem is not as bad as some predict and one way to eliminate it if it bothers you is to install multiple smaller tanks which also provide increased security for the water supply.
Cheers,
Peter
OKA196 motorhome
 

cameronsturgess

Active member
If you go with poly tanks, consider a "welded" in metal insert threaded to accept your drain plug. It's pretty easy to foul threads in plastic materials if one even slightly over tightens a bung. If you have the space you could also consider a low profile valve for your drain plug and avoid thread problems all together. We've found we use the drain plug more than expected:

1. Removing all water from external tanks in winter.

2. Accessing water in the tank when some plumbing/pumping problem develops.

Howard
great idea Howard.. thanks
 

cameronsturgess

Active member
So you are adding 900#. How does that work with your GVWR ?
But to the question, I'd go with a "Potable Water Food Grade" poly tank.

Might depend on how far, often, remote you travel. Heading for 3 years in Africa or South America I would likely pick SS
thanks for recommendation.. yes we should be ok with weight
 

cameronsturgess

Active member
I have 2 commercially sourced HDPE water tanks (70L each and 3mm wall thickness) plus 2 DIY rotationally moulded HDPE water tanks (55L each and 5mm wall thickness) plus 2 DIY rotationally moulded HDPE fuel tanks (80L each and 10mm wall thickness) plus one commercially made SS water tank (100L).
The SS tank fatigue cracks and I will replace it with another DIY rotationally moulded HDPE tank.
I use spin welded threaded fittings in the HDPE tanks. The DIY HDPE tanks have all been in use for 14 years.
Never had a taste issue and we regularly add chlorine as we fill.
I think the "sloshing" problem is not as bad as some predict and one way to eliminate it if it bothers you is to install multiple smaller tanks which also provide increased security for the water supply.
Cheers,
Peter
OKA196 motorhome
Peter I had no idea you could roto mold your own tanks.. very cool !
 

cameronsturgess

Active member
I went with 10mm HDPE welded tanks. I have 6 tanks of various shapes and sizes to make maximum use of the available space, about 600 lts of fresh and drinking all up plus a grey tank, no black. Didn't fit any baffles

The guy who made them gave me a lesson in how to repair a crack if ever needed but hopefully not.

Stainless was dearer plus was worried about corrosion.

I have one tank above the DPF so fitted a heat guard.
thanks Steve :)
 

Peter_n_Margaret

Adventurer
Peter I had no idea you could roto mold your own tanks.. very cool !
Well, not quite.:rolleyes: Although it is technically possible.
I made the moulds (from 2mm bright mild steel sheet) and had a moulder do the rest for me.
Some of the benefits of rotomoulding are that there are no seams at all and a single simple mould can be used to make multiple tanks, all with different wall thicknesses if that is desired for different applications.
I do my own spin welding of threaded fittings.
Cheers,
Peter
OKA196 motorhome
 

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