Excellent installation of hotun hiflo with a boiler, by Luke Beard

For boilers hotun hiflo dry trap tundish with hotun shield provides the perfect solution

Connect the boiler’s pressure relief valve (PRV) through hotun hiflo dry trap tundish (with hotun shield as a safety feature) and then direct to a local waste or foul drain, without odours ventilating back into the building.

Worcester Bosch, Vaillant UK, Glow Worm Club, Ideal Heating, Ariston and KD Navien all allow the use of hotun hiflo dry trap tundish (with shield if boiler is located in an accessible location) to safely discharge the boiler’s PRV and, when applicable, to combine the condense into the same single pipe discharge below the hotun for a compliant* connection.

Product Features – hotun hiflo

  • 126mm tall x 57 mm wide
  • 1/2″ flat face tap connection on inlet
  • 32mm HDPE or universal/compression compatible outlet
  • Allows trickle** and full-bore discharges up to 18 l/m
  • Temperature rated up to 100?C
  • Air break to drain
  • Safe and visible means of discharge
  • 5 year warranty (T&C’s apply)

Product Features – hotun shield

  • Discharging water can be seen clearly
  • Made from 100?C temperature rated clear temperature rated thermoplastic (SAN – Styrene Acrylonitrile)
  • Makes siting tundish in accessible areas safe
  • Ultra tough
  • Simple and secure drop-over design
  • Once top connection is made, shield is held securely in place
  • Any discharging high-temperature water cannot be touched

Commonly called: odour seal tundish, dry trap tundish, trap tundish, tundish boiler, tundish valve, overflow tundish trap, dry odour seal tundish, sprung valve tundish, non return tundish

hotun’s patented and simple, but visually appealing style, has many advantages over other more expensive and bulky options

  • To go to the alternative compliant options page, click here
  • There?are no specific regulations governing the discharge from the boiler PRV. However good practice should always be followed and it is our view that guidance from G3 (unvented) regulations should form the basis of installation? for boiler PRV’s with one major difference, the total discharge of water from a boiler is significantly less than the potential from an unvented T&Prv, therefore the choice of waste pipework material may be wider. With this in mind, however, it is still down to the installation engineer to ensure a fit for purpose installation.
  • To see some video clips of hotun discharge flow tests (trickle and full-bore), click here
  • To view the full operation, installation, service and warranty instructions, click here
  • For typical boiler installation types, click here

* Provided that the waste and/or foul stack can be demonstrated to be able to withstand the effects of the expected temperatures, pressures and volumes being discharged.

Note. A sealed system, such as a heating circuit, will only discharge to the waste system to relieve the excess pressure. The amount of water released will equate to the volumetric increase in relation to the temperature/pressure rise governed by the co-efficient of expansion of water. In a boiler circuit, the volume discharged to relieve the pressure build up will vary with the system volume and should be calculated to suit the individual installation.

Therefore, unlike Unvented cylinder systems that are mains connected, sealed, pressurised systems will only release minimal discharges of water at intermittent intervals. The ability of the waste discharge system to be able to withstand these volumes and temperatures should be viewed in a different way to the way a discharge from an unvented cylinder D2 waste pipe is looked at.

Please note, Polypropylene (PP- push fit and most mechanical couplings), High Density Polyethylene (HDPE) and MuPVC?or more latterly labeled PVC-C or C-PVC (solvent weld) are generally accepted by building control to be suitable for use on Unvented cylinder D2 discharges, therefore the use of these particular materials would be preferable because they are accepted to be capable?of withstanding far more onerous working conditions than boiler applications.

For other pipework materials, consideration must be given with regards to the above physical conditions of operation. However, if in doubt, please contact your local building control for advice before installation.

** The spring/valve/diaphragm assembly is precisely engineered to hold the diaphragm shut under normal operating conditions (to prevent odours being ventilated back up from the foul waste pipes or drain), but still allow the valve to open with a minimal quantity of water in the upper chamber. We call this the trigger point and is set to release at between 5ml and 25ml of water. The upper chamber will hold 50ml of water before overflowing.

hotun hiflo – the tundish evolved