A Blog by Russell Armstrong

(inventor of the hotun dry trap tundish)


When I first started on product development for hotun, it was with one application in mind, that of connecting the PRV discharge from a small unvented hot water cylinder to a local waste pipe or drain, little did I know about the possibility and wide & varied applications there were going to be!

Investment – faint heart does not win the fair maiden

Once the design had been tested with 3D technology prototypes, we proceeded (at some considerable expense), to commission the relevant tooling & IP protection. For a one-man band plumber, such as myself, this was a huge investment. In fact, I could have brought a modest-sized house in my local city (Derby) for the money I put into our first product. So I put what was, in effect, our life’s savings (myself, wife and a loan from my parents) into the venture.

I assure you this is not for the faint-hearted!

Within weeks of launch, I was asked by an installer in Scotland, if hotun was suitable for boilers? The long and short of it was a split decision by two boiler manufacturers. Luckily for me, it was Worcester Bosch who said my idea had potential and could they test hotun for use on their boilers

Product Development – Upgrading

The hotun (15/22) did not cope with the full flow! We found that due to its design it would pass comfortably 12 litres per minute & at a push 16LPM but not the 18LPM that came out of the Worcester boiler.

Undaunted, I went away to develop hotun and came up with hotun hiflo (15/32). In our extensive tests, we found that the hiflo unit could easily cope with 18LPM and went upwards of 20-22LPM at a steady-state full flow volume.

The two most important aspects of the performance of our dry trap tundishes were, could it handle trickle flow (valve opens to let water pass into the waste pipe) and did it cope with water at full bore discharge, because that was part of the regulatory criterion.

Dry Trap Tundish - hotun hiflo 100C - 15x32 - White - Product Code HHW100C - Single Product - Cutout - Image with logo

Therefore we had a resounding yes from Worcester Bosch, who then stated that they would accept hotun hiflo for use with their boilers!

Happy days? – You would have thought so

However, plumbers do not appear to be happy to accept your first offerings at face value. Right from launch, the market had taken our concept and was already giving us feedback about our products, some in a constructive manner others less so. That being said we knew there were several points that would take us forward if only we could incorporate them to achieve the following design & business elements

  1. They worked better than existing
  2. Still looked aesthetically pleasing (for a tundish!)
  3. Could still be easily manufactured
  4. The manufacturing cost was within reasonable limits so as to be affordable to the end-user


What we achieved (and it took some 18 months of development work) is a remarkable collaboration with one of the UK’s best-known push-fit range of pipe connectors, JG Speedfit. They were more than delighted to be associated with our product and gave us permission to use their “Speedfit technology” branding.

We looked extensively at flow dynamics both on the inlet and outlet side to see what could be done to improve flow.

With the “100”?range we stated clearly that our units would flow 12 & 18LPM respectively and gave guidance as to what that meant but were pushed from day one to do more. The plumbers out there were putting our products on PRV’s that discharged almost 25LPM! So they demanded more from the hotun (which is an absolute compliment when you think about it,?considering that before we came along they had no other single product to do the job!)

Onwards & Upwards

Be that as it may, plumbers shouted to us to be better, if 12/18 was good, 25 would be better! Please give us more & more. It is a testament to our success that the product had found a good market and rather than say it was a rubbish product, they just wanted it to be better

Unfortunately, due to reasons of confidentiality, we couldn’t tell people about our development plans, no manufacturer would. We said we were listening and that, when the time was right, we would bring something to the market. It’s an interesting dichotomy, having introduced an invention that grabbed the market by storm, got everybody excited about the new possibilities, they demanded that it could still be better.

Funnily enough, we agreed that things could be better. If we could achieve this 25LPM landmark, our product would have an immediate wider appeal. However the market was impatient for the new product, but they didn’t understand how long it takes to go from iteration 1 to iteration 2

When you change things everything has to be re-tested, that costs money, lots of it and as an embryonic company money was in short supply, this delayed things, so much so that although we had tested and developed our new range, the cost of tooling would have to wait and wait it did (frustratingly for us)

But as the infographic (below) shows the wait and product was worth it. With flows up from 12 & 18 to 16 & 25LPM with an additional 22/32 (hotun XLSF) added into the range at a rated flow of an incredible 40LPM we now boast a market-leading range of dry trap tundishes that will cope with almost every application that there is out there! (well in the domestic to medium commercial market place)

Are we pleased with this? Hell yes!

What were we asked and what did we achieve?

We were asked to;

  1. Include a nut & olive on the 22mm outlet version
  2. Provide an inlet connection
  3. Improve flow to cope with ANY application
  4. Give alternative (less expensive) options for connection to the discharge
  5. Keep the costs of the unit affordable to the end-user (and from a supply chain point of view keep margins)

What did we achieve?

  1. All models (100 & SF) with a 22mm outlet now come with a nut & olive supplied as standard
  2. The SF range has an inbuilt speedfit connection (we still sell the threaded inlet 100 range for those that don’t want speedfit)
  3. We improved flow from 12 & 18 LPM to an incredible 16, 25 & 40 LPM?respectively
  4. The outlet on our unit is now compatible with industry-standard push-fit waste systems (as well as universal compression, it is after all universal for a reason!)
  5. The new product range sells, at a merchant near you, for between 18 & 21

Have we achieved our goals? Well, only you can decide. All we can say is that we are pleased with the outcomes


RA Tech hotun dry trap tundish SF Range Product Group Image

The market spoke, we listened, we developed!

#hotun – It’s not just a tundish


Get In Touch

Registered Address

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

T: 01332 702678
E: info@ratechuk.co.uk



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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