NP overflow

The Importance of plumbing your overflow and warning pipe correctly

What happens if a GRP Sectional tank is plumbed incorrectly?


Understanding the importance of correctly installed warning and overflow pipes will help in limiting water damage in buildings.

Warning pipes and overflows that are not plumbed correctly can lead to thousands of pounds worth of damage. Failure to plumb the warning pipe to a monitored area may lead to faults going undetected for long time periods. The role of the warning pipe is to alert personnel of rising water levels in the water storage tank, indicating a fault or malfunction with the inlet or other connections. If undetected, water levels will continue to rise and exit the tank through the water tank overflow. It is vital that the overflow is correctly piped to a gully or bunded area to accommodate overflow water and avoid flooding, water damage, and possible costly repairs.


Standard plumbing example

Overflow Animation

WRAS warning pipe and overflow guidelines

‘Warning pipe’ means an overflow pipe with its inlet located in the cistern at such a height that it will start to flow before the main overflow operates and with its outlet located in a position where the discharge of water can be readily seen.

Source WRAS

Wherever possible warning pipes should discharge outside a building, however where this is not practicable owing to the design of the building, they may be discharged internally provided the discharge is conspicuous. View the WRAS regulation guide for examples of acceptable arrangements for the discharge of the warning/overflow pipe.

Source WRAS Regulations Guide

For more information please review our recommended WRAS guidelines below. We offer water storage solutions for all applications contact our sales team or view our products page for more information. For more information on our range of cold water storage tanks available visit our products page, alternatively please give our team a call for correct tank selections for your job.

Benefits of working with Nicholson Plastics

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Expert Leading

Manufacturing GRP cold water storage solutions for domestic, industrial, agricultural & commercial industry sectors since 1968. 

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CPD Training

We have created a CPD training course to develop and improve industry professionals with the correct skills in specifying water storage solutions.

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ISO Certified

Our cold water storage tanks including WRAS approved, are manufactured to the highest quality and ISO standards.

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Team Tank Care+

We provide a dedicated customer support team to help with technical queries including drawing returns, delivery, installation & site support.

Cold Water Storage Tank Solutions

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Sectional Tank

✓ Highest quality standard

✓ Bespoke design

✓ UV stabilised materials

✓ WRAS approved

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Combined Sectional Tank Enclosure

✓ Very Compact

✓ Professional enclosure

✓ GRP material

✓ Corrosion resistant

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One Piece Tank

✓ Bespoke design

✓ Virtually ZERO maintenance

✓ Can be supplied in any BS5252 or RAL colour

✓ WRAS approved

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Break Tanks

✓ Available from a standard range 

✓ Pre-insulated tanks

✓ Standard capacities are available

✓ WRAS approved

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Two-part Tanks

✓ Manufactured to order

✓ Available with insulation in varying thicknesses

✓ Fully self-draining

✓ WRAS approved

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Category 5 Tanks

✓ Uses for urinals, laboratories, drain cleaning plants, industrial cisterns and bins, etc.

✓ UV stabilised materials

✓ WRAS approved Type AB - Air gap

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City Tanks

✓ Maximise availalable floor space

✓ Quick assembly timelines

✓ Any volume of water

✓ Customisable shape configurations

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Cube Tanks

✓ Self-Assembly (1x1x1 meter panels)

✓ Easy access for restricted spaces

✓ Can be assembled against three walls

✓ Easy to transport on one pallet

Why work with us for your Water Storage Needs?

Over 50 years’ industry experience

Projects completed in the last 24 months

Nicholson Plastics is a UK GRP Cold Water Storage Tank Manufacturer with a proven track record in the supply of water tanks to all industry sectors throughout the UK. We have an expert team on hand with over 50 Years' industry experience. Our team works hard to provide exceptional industry lead times from quotes, site visits, order processing, and delivery. We are a British Standard approved company with full certification through BSI/ISO9001 including WRAS approved certified products for potable drinking water.

  • Over 50 years of technical knowledge.
  • Quality assurance at a local level.
  • UK customer support teams, backup, replacement service & advice.
  • Supporting local and sustaining UK manufacturing.
  • Regional sales representatives for site visits, emergency water requirements, and project advice.


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Government Buildings


Our Accreditations

At Nicholson’s, we pride ourselves in manufacturing and installing GRP water storage solutions of the highest quality throughout the UK. To see our certifications - Click here.


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bsi member cert
Certified ISO company
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chas accredited contractor
safe contractor approved