The hotun dry trap tundish story

The hotun dry trap tundish, has been developed by RA Tech UK Ltd, a company founded by experienced and respected plumber Russell Armstrong (Member of the Chartered Institute of Plumbing and Heating Engineering – CiPHE) and this is his hotun product development story

Russell’s long experience in the building industry has led him to understand the practical problems that installers and tradespeople face when driven by the demands of certain regulations. The introduction of new products to meet those regulations is a challenge in itself and to devise a simple and effective way to solve a problem is what Russell set out to do.

Having come up with the idea of hotun, he formed his company, with fellow director (and wife) Ally Armstrong, RA Tech UK Ltd. He has invested in patenting the product, testing it fully, and getting it approved by all relevant industry bodies. A major investment in design, development, testing & tooling and then, commissioning all manufacturing to local ISO9000 companies. This means that hotun can be specified and installed with confidence, and is offered with a 10-year warranty.

The Story – The Start 2012

In his plumbing role, Russell was carrying out an unvented hot water heater, that had a pressure relief device as a safety feature to prevent over-pressures from developing in the unit. To provide that, the installation required a tundish (to provide the regulation required visibility of water dripping from a safety valve) but also some sort of product that allowed flow but stopped smells coming back up from a foul drain, as the discharge line had to be connected to a drain. It had to be in a compact design that fitted the space available. Russell wanted a simple all in one product solution and despite scouring the market he could not find something that fitted the bill.

As a designer and not finding a suitable product available, an idea was born and armed with his skills in drafting and design, Russell took pen to paper and sketched out a drawing that, to this day, bears all the hallmarks of the original concept, those concepts went on to become hotun, the product was so original it became patented.

To find out more about Russell please view his LinkedIn profile 


Original design & the Regulations

The issue that Russell faced was to make sure that the product complied with all Building & Water Regulations, which during the design phase was the most tricky part to do.

There were 7 major regulations (for unvented water heaters) that he had to overcome, to provide a one-product solution are laid out on the page, here 

Not only did hotun have to comply, and work, but also needed to be value for money and easy to install

With the aid of 3D printing technology, Russell produced his very first prototype (see picture left) with its bolt, spring and valve.

Every component in hotun is a bespoke design. He has used British based companies to work with to help develop the product, from a spring and diaphragm to the bolt assembly, all uniquely designed specifically for the product.

We are proud to boast that all of our hotun products are 100% designed, manufactured and assembled in Britain and are members of the official Made in Britain organisation community

Design development & launch – 2015

The original design turned out to be the easy part. Turning the concept into a product that could be injection molded was a job 18 months in the making. 3D printing allows designs to be produced quickly but does not reflect the mass production process in terms of injection molding limitations.

Russell commissioned a local company to carry out that design and after several iterations we were ready to place an order for the very first hotun tooling

In April 2015 RA Tech UK Ltd introduced to the market the hotun dry trap tundish, it was to become, and is, an industry revolution – The hotun revolution

In every aspect of the story, the introduction of hotun has irrevocably changed the way that pressure relief valve discharges are now fitted in the boiler market and, to coin a phrase;


hotun – its not just a tundish


Eternal thank you’s!

To Tex Plastics (Derby) for believing in me as a budding inventor and for supporting me with the manufacturing skills, through all the intervening years

To Willbond (Derby) for having the faith and becoming the very first commercial plumbers merchant to take my products on board in the #hotunrevolution 

To Travis Perkins and City Plumbing for our very first accolade and professional industry success being the “Travis Perkins Innovation Awards” (TPIA) Winner 2016

and most of all, to all of our tens of thousands of installers who, without you, our product wouldn’t be the success it is


Since developing the hotun product, Russell has spent more and more time away from his actual plumbing business, to the extent that he is now working full time at RA Tech. His plumbing business has taken such a back seat that it no longer makes sense to keep the company running and as such, he has closed that business.


Patented, Pioneering Products

Get In Touch

Registered Address

RA Tech UK Ltd
6 Nottingham Road
Long Eaton, Nottingham, UK

T: 01332 702678



In one simple fitting, hotun solves the problem of compliantly running a PRV valve discharge from a pressurised hot water cylinder relief valve or boiler pressure relief valve to a local waste or soil pipe.

hotun combines a tundish and a non-return valve to make a dry trap tundish which acts as a visible early warning device and prevents foul odours from escaping from the waste/soil pipe.


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