Lisa Westlakes gravatar image

Water tank construction in Nepal

by Lisa Westlakes | 2017-09-14 11:03:46 -0500 | related country: Nepal

Has anyone used HDPE tanks in Community Water Projects in Nepal? We need a 10 000 litre tank and I was going to use ferrocement due to availability of materials, reduced transport costs, repair ability etc, but other project team members are keen to use an HDPE tank, I don't think HDPE tanks this size are readily available and am concerned about longevity?

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kabindrapudasaini@wateraid.org gravatar image

by kabindrapudasaini@wateraid.org | 2017-09-21 20:24:31 -0500

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In Nepal ,although the availability of HDPE tank of Capacity 10000 liter is available in urban areas like Kathmandu city, Biratnagar, Birjung ect. But Main challenging is for transport in rural communities. some problem in HDPE tank big in size, difficult to installation and can be affected by Wind also and community people will realized this is the temporary solution to storage water in their system. When constructed fero cement, they realized their system are now permanent. due to easily construction with less materials, can be constructed by local workers, can be constructed in different size due to availability of land and easy to operation and maintenance and less risk by leakage due to outer activities( HDPE tank can borke down by making hole even by children during playing), so most of rural setting, most common ferocement tank. Thank you

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kabindrapudasaini@wateraid.org gravatar image

by kabindrapudasaini@wateraid.org | 2017-09-22 00:56:21 -0500

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Dear Lisa, Yes Plastic tank ( HDPE) of 10000 liters capacity can be ordered by regular suppliers, it was even supported by India after earthquake in Nepal in 2015.And limited quantity can be manufacture even in Nepal. In some communities , such tank are installed and supplying community water after earthquake.

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John Cody gravatar image

by John Cody | RedR Experts | 2017-09-20 11:41:51 -0500

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Hi Lisa HDPE tanks of that size should be fine and the life should be comparable to a ferrocement tank. There should be no problems with toxicity. You may want to factor in a sun shade into your costing, black tanks in particular get get quite hot.

HDPE tanks were avaialable outside of Katmandu in 2015, though the maximum sizes that I came across were 1,000 litres, and they were expensive. IF the construction is not time critical and the the skills and materials for a ferrocement tank are readily available I would opt for the ferrocement for a tank that size. As I recall these were commonly used by the District Water Offices in rural schemes, and there were established standards in terms of design, material and construction. The standards should be easily available from your DWO, and they are likely to be able to assist with a technician experienced in constructing ferrocement tankls to standard- you will probably need to provide a per-diem.

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John Cody gravatar image

by John Cody | RedR Experts | 2017-09-20 11:40:38 -0500

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Hi Lisa HDPE tanks of that size should be fine and the life should be comparable to a ferrocement tank. There should be no problems with toxicity. You may want to factor in a sun shade into your costing, black tanks in particular get get quite hot.

HDPE tanks were avaialable outside of Katmandu in 2015, though the maximum sizes that I came across were 1,000 litres, and they were expensive. IF the construction is not time critical and the the skills and materials for a ferrocement tank are readily available I would opt for the ferrocement for a tank that size. As I recall these were commonly used by the District Water Offices in rural schemes, and there were established standards in terms of design, material and construction. The standards should be easily available from your DWO, and they are likely to be able to assist with a technician experienced in constructing ferrocement tankls to standard- you will probably need to provide a per-diem.

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RedR TSS gravatar image

by RedR TSS | RedR Experts | 2017-09-20 10:39:08 -0500

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Hi Lisa

By "ferrocement", I presume you mean a 0.4: 1: 2 :: water: cement: sand mortar, hand applied to an armature of reinforcing bars and several layers of mesh, to form a thin (20-40 mm thick) shell deriving its strength mainly from membrane action rather than bending?

The benefits of this form of construction are that the materials and workmanship skills should be readily available in Nepal and easily transportable to the site that may be difficult to reach.

The optimum shape for such a form of construction is a membrane shell, like a boat hull, arch or, for liquid containment, circular with an inverted dome base. If a rectangular shape is required or desired for any reason, the bending is best resisted by an external structure (eg: a reinforced concrete base with gravity or reinforced concrete walls), using the ferrocement lining as a waterproof skin, able to bridge over local structural weaknesses (in the external structure). The composite action between the two is enhanced by shaping all external edges to form a curved bevel and internal edges to form a fillet, each of radius about 150 mm.

The other important thing is the mortar mix: the water cement ratio should be as low as possible that makes the mix workable; if the "sand" is too sharp (as crushed rock would be), the cement content should be increased maintaining the water: cement ratio at 0.4.

If you would like construction details, let me have details of the site, size of the tank, input flows and demand.

Look forward to hearing from you...

Kind regards, Leigh

LC Jones

RedR KnowledgePoint Moderator

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Harriette Purchas gravatar image

by Harriette Purchas | RedR Experts | 2017-09-20 09:50:46 -0500

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Hi Sarah, If you go onto the DWI website by following this link:

http://www.dwi.gov.uk/drinking-water-...

you will find that apart from the products listing, which lists all of the products certified for use in the UK, there are also sections that deal with frequently asked questions and advice on the approval process which tells you how this process works. As for the testing this is carried out by a specialist material testing laboratory which is certified to undertake these tests. Payment for such testing is the responsibility of the manufacturer of the product as they are the ones who benefit from their product being approved for use in contact with drinking water. Ie they can advertise their paint can be used in these situations. Almost certainly therefore if a product is approved for use and has been tested to get his certification then the manufacturers will want to advertise this. Clearly each country might well approach this in a different way so I can’t really help you with this.

Hope that's helpful

Regards Harriette

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ErikH gravatar image

by ErikH | WaterAid Partners | 2017-09-20 08:28:06 -0500

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Lisa

In general a high quality HDPE tank (roto moulded) should have a life span of 10-15 years. A ferrocement tank may last as long, but it also may well sprout some leaks and need repairs sooner. You could argue that this might therefore be more sustainable as repairs can be made locally, but my experience they rarely are.

At a quick check with a Nepalese colleague in the office he thinks plastic tanks are available locally (in the cities) and that these would come in from India. So you will likely pay a premium and may also have transport to arrange.

I have asked a colleague from our office in Kathmandu to add more.

Hope that helps

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Asked: 2017-09-14 11:03:46 -0500

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Last updated: Sep 20