We at Dewey Waters will endeavour to answer all of your questions regarding legislative issues or our product range and services.

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Water Tanks, Biofilters & GRP Housings

Warranty Statement


All Dewey Waters Limited products are fully warranted in respect of workmanship and materials for twelve months from the date of installation for sectional tanks, and receipt of goods for all other products. Outside this period Dewey Waters Limited will investigate and rectify problems upon request but reserve the right to make a charge for these services to be determined at the time. Extended warranties are available by negotiation.

It would be expected under normal conditions of service that Dewey Waters Limited GRP potable water storage tanks and static associated peripherals would have a maintenance free service life in excess of twenty years. Moving parts, such as valves, would be expected to require servicing / replacement as recommended by the manufacturer thereof. Operation and maintenance statements for sectional and one piece GRP potable water storage tanks are available from Dewey Waters Limited.

What’s the difference between nominal and actual capacity?

The nominal capacity is the volume of the tank when it is filled to the brim. The actual capacity is the volume contained within the tank up to the maximum working level. This is dependent on the inlet size and air gap selection.

What does variance mean when calculating a water tank size?

Variance describes how much a random variable differs from its expected value. Variation is included on the calculator inputs to give you additional tank options if you are trying to achieve a ball park figure rather than an exact one. Example: If you needed approx 1000 litres you might put in a 10% variance and it would give you tanks between 900 & 1100 litres rather than just a 1000.

What's a type AB air gap?

This is a non-mechanical backflow prevention arrangement. The water is discharged through an air gap which has at all times an unrestricted spillover to the atmosphere. This is required to protect the mains water supply from back siphonage of a category 5 fluid application such as Process, Medical or Grey water recycling systems.

What does TIF, IFB and EFB stand for?

They are all acronyms relating to the flanges of our sectional tanks.

  • TIF – Totally Internally Flanged (all internal bolting)
  • IFB – Internally Flanged Base (externally flanged sides)
  • EFB – Externally Flanged Base (externally flanged sides)
What space do I need around my tank?

This will depend upon the type and height of tank you require, an approximate guide as follows:

  • IFB under 2m high – 500mm on all 4 sides and 750mm* above
  • IFB 2m > 3m high – 800mm on all 4 sides and 750mm* above
  • IFB 3.5m & 4m high – 1000mm on all 4 sides and 750mm* above
  • EFB under 2m high- 500mm on all 4 sides, 600mm underneath and 750mm* above
  • EFB over 2m > 3m high- 800mm on all 4 sides, 600mm underneath and 750mm* above
  • EFB 3.5m & 4m high – 1000mm on all 4 sides, 600mm underneath and 750mm* above
  • TIF – 50mm on 3 sides, 500mm on 1 side and 750mm* above

*1200mm when fitted with a Guardrail 

Please note the clearance above can be reduced to a minimum of 500mm with the inclusion of a ‘lift off kit’. The clearance around tanks over 2m can be reduced depending on site conditions. Please speak to our technical sales team on +44 (0) 1934 421477 for further information.

Can I store wholesome potable water within your tanks?

Yes, Dewey Waters have full WRAS approval and manufactured to British Standards, for our full range of one piece and sectional water storage tanks (not including underground).

Why would I need a totally internally flanged tank?

Standard access requirements request a minimum clearance of 500mm around all four sides of the tank for assembly and maintenance purposes. With the TIF design these access requirements are reduced to 50mm on three sides and 500mm on one side. The tank may be positioned up against a wall or column, allowing space for other equipment within the plant room.

Do you have stock products available?

Yes, we hold a selection of One Piece Tanks with standard insulation recess positions (areas that connections can be fitted within). 

What is your maximum height tank?

This is currently 4m for Hot Press Sectional Tanks, 3m for our Totally Internally Flanged tanks and 2.2m One Piece Specials, however, we are always striving to develop our products and manufacturing methods.

What thickness of insulation do you offer?

38mm as standard (0.57w/m2/⁰C), 50mm (0.40w/m2/⁰C) is also available

Totally Internally Flanged Sectional Tank

25mm as standard (0.85w/m2/⁰C), 50mm (0.40w/m2/⁰C) is also available

25mm as standard, 50mm (0.40w/m2/⁰C) and 75mm (0.27w/m2/⁰C) are also available

GRP Tank Manufacturer & Supplier with over 60 Year Experience

Dewey Waters is one of the UK’s market leaders in the manufacture and supply of all cold water storage tanks. We specialise in sectional tanks (1,000 to 1,500,000 litres) and one piece tanks (from 30 to 9000 litres) we offer standard size tanks or custom built tanks to suit individual project requirements. We also provide a range of other GRP manufactured products including housings and biofilters, as well as kiosks and cabinets. We provide full project management for jobs of all sizes and also offer our clients training on the installation of water tanks. GRP Tanks are ideal in the storage of cold water offering a durable solution which can withstand heavy impact, weather conditions and heavy loads.