Why Do We Use GRP Water Tank - Landyoung Group Co., Ltd.

25 Aug.,2025

 

Why Do We Use GRP Water Tank - Landyoung Group Co., Ltd.

GRP water tanks, short for Fiberglass Reinforced Plastic water tanks, are the market-leading standard water storage devices for industrial and residential use. With many advantages such as lightweight, robust construction, modular and sectional assembly with standard panel design, GRP tanks provide a safe environment without the risk of bacterial corrosion.

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In addition, the raw materials used to manufacture the tanks themselves are resistant to harsh weather and high temperatures, which means that the tanks have a long service life. At the same time, the properties of all the raw materials determine the flexibility of the tank for any particular visit or need.

FRP (also known as fiberglass or GRP) is a fiber-reinforced polymer made from a plastic matrix reinforced with fine glass fibers. It is an inexpensive, lightweight, extremely strong, and robust material that can be easily molded using a molding process. This is the reason why more and more traditional water tanks are being replaced by GRP water tanks.

 Stainless Steel Water Tank

The individual glass fiber structure is stiff and strong in both tension and compression, that is, along its axis. While one might think that the fiber is weak in compression, it is actually only the aspect ratio of the fiber that makes it appear so; that is, because the typical fiber is long and narrow, it bends easily. On the other hand, glass fibers in shear-that are, across their axis-are not stiff and strong. Therefore, if a collection of fibers can be permanently aligned in the material in the preferred direction, and if the fibers can be prevented from flexing in compression, the material will become preferentially strong in that direction.

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Sounds good, which is why so many companies choose to replace old water tanks with GRP tanks. However, most of our rework is done on GRP tanks and we would like to share why.

Mastic erosion

Cement erosion occurs when the joints and steel bolts holding the panels together begin to corrode and subsequently provide a safe harbor for bacterial growth. The permeable blistering of the GRP substrate due to water penetration can also lead to deterioration of the gel coat and subsequently, the surface is highly likely to harbor and promote the growth of microscopic aquatic organisms. This can be a very serious situation because if ignored, this internal water-permeable blistering can eventually rupture and release its contents into drinking water. Not only do these chemicals have a very unpleasant odor, but they are also dangerous if they come into contact with people.

 GRP Tanks 

Fungi and molds

Black spore fungus is often found in worn-out GRP tanks that need repair. It can be extremely difficult to remove if not treated at the right time, which is why regular audits of the tank are recommended. Black spore fungus, like all molds and fungi, is very common in the UK as it is often cold and wet, which is a perfect breeding ground - much like water tanks. Mould is a health hazard and should be dealt with appropriately.

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New Water Tank - Stainless or GRP? - Cruisers & Sailing Forums

Registered User
Join Date: Aug Location: Houston, Texas Boat: Morgan Out Island 416
Posts: 157 Images: 1 New Water Tank - Stainless or GRP? I just removed the port side (75 gal) water tank from my Morgan 416. Old polyethylene Tank came out largely intact (had to cut one upper corner off so it would fit thru hatch).

Question is: should I replace with a stainless steel fabricated tank or build a fiberglass one, using vinylester resin with an FDA approved catalyst to kick it off and building the glass tank over the old poly tank as a mold (with appropriate mold preparation). Registered User
Join Date: Oct Location: Cruising the southern coast of Portugal and Spain Boat: Leopard 40
Posts: 764 Some of the newer cats are going to stainless steel as a safer option than either plastic or poly. I don't know if chemicals leach into the water from the poly but if you decide to use plastic I'd check to see if it is made with BPA.

Maje Moderator Emeritus
Join Date: Aug Location: Carlsbad, CA Boat: Sabre 28-2
Posts: 7,505 Stainless suffers from external pinhead corrosion if they are constantly in salt water such as tanks in the bilge. Mine only lasted 4 years. They also can suffer internal pinhead corrosion which is what usually kills SS fuel tanks.

The fiberglass tanks on my current boat are still going strong after 40+ years.

I'd still think about plastic tanks if one is available. Would assume that would be the case since your previous tank was plastic. Registered User
Join Date: Jan Location: Usually where the boat is... Boat: Pearson 40
Posts: 557 Images: 7 If you can build a tank out of epoxy and glass and coat the inside with a food grade epoxy (to avoid the amine blush released by the epoxy curing process), the tank should last virtually indefinitely. I can give you the address of a good, commercial grade epoxy tank coating used for drinking water if interested.

Only problem would be from reverse osmosis, i.e water penetrating from the inside to the outisde of the tank. However with an epoxy tank and proper coating this should not be the case.

Building a tank out of glass is time consuming, however. Materials should be about half of what a new poly tank would cost but with those, welds are sometimes an issue and are not always an easy fix. Moderator Emeritus

Join Date: Sep Location: Eastern Tennessee Boat: Research vessel for a university, retired now.
Posts: 10,405 I replaced two stainless steel fresh water tanks that corroded out. I replaced them with polyethylene tanks. I thinks it's the best material for this application. The fiberglass tank you are considering could quite possibly cause your water to taste or smell like the resin you use.

Here is an idea of the cost. I can't imagine it being worthwhile to make your own unless the space is not a rectangular shape and you are trying to maximize the tank volume
http://www.plastic-mart.com/class.php?cat=12 __________________
David

Life begins where land ends. Registered User
Join Date: Jan Location: Usually where the boat is... Boat: Pearson 40
Posts: 557 Images: 7 Epoxy Coating Hello

Are you still in West Palm Beach?

If so, Glue Products (I remember they were on Australian Ave) might still deal with food grade coatings.

I know they are still in business, we used to buy epoxy from them back in the late 80s...

Let me know if not, there is a good place in NC that we used about 5 years ago when we coated our tanks (with good success).

Regards Registered User
Join Date: Jan Location: Bundaberg, Australia Boat: 57ft Steel Expedition Vessel
Posts: 174 From a health point of view I would go stainless, We have poly tanks (with no BPA) however plastic leaches into your water (even if you cant taste it) the hotter the tank the more it leaches. Yes stainless has its draw backs (cost etc etc) however why risk cancer for a few hundred bucks...


I know this wont be a popular opinion (and it is just that) however health is a factor that's never really factored in.

Damien