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PLUMBING SYSTEM INSPECT DIAGNOSE REPAIR
AGE of PLUMBING MATERIALS & FIXTURES
AIR DISCHARGE at FAUCETS, FIXTURES
ANTI SCALD VALVES
ANODES & DIP TUBES on WATER HEATERS
BACKUP PREVENTION, SEPTIC
BACKUP PREVENTION, SEWER LINE
BACKWATER VALVES, SEWER LINE
BATH & KITCHEN DESIGN GUIDE
CHEMICAL CONTAMINANTS in WATER
CHEMICAL ODOR SOURCES
CHLORINE IN DRINKING WATER
CLOGGED DRAIN DIAGNOSIS & REPAIR
DEBRIS in WATER SUPPLY, Water Heater
DEPTH of SEPTIC TANK
DRAIN & SEWER PIPING
FAUCETS & CONTROLS, KITCHEN & BATH
FAUCETS, OUTDOOR HOSE BIBBS
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOR DRAIN / TRAP ODORS
FLUSHOMETER VALVES for TOILETS URINALS
GAS PIPING, VALVES, CONTROLS
GALVANIC SCALE & METAL CORROSION
HARD WATER - SOFTENERS
HEAT TAPES, Heat, Insulation prevent Freeze-Up
LEAD POISONING HAZARDS GUIDE
LEAD IN DRINKING WATER, HOW to REDUCE
METHANE GAS SOURCES
MIXING / ANTI-SCALD VALVES
MUNICIPAL WATER PRESSURE IMPROVEMENTS
NOISE / SOUND DIAGNOSIS & CURE
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
ODORS, SEPTIC or SEWER
ODORS SEWER GAS in COLD WEATHER
ODORS, SULPHUR SMELL SOURCES
ANIMAL or URINE ODOR SOURCE DETECTION
PIPING IN BUILDINGS, Clogs Leaks Types
PLUMBING FIXTURES, KITCHEN, BATH
PLUMBING NOISE TRANSMISSION CONTROL
PLUMBING VENT DEFINITIONS & CODES
PLUMBING VENT DEFECTS & NOISES
PUMPS USED in BUILDINGS
PUMPS, WATER REPAIR
RELIEF VALVE LEAKS
RELIEF VALVE, TP VALVE, BOILER
RELIEF VALVE, TP VALVE, STEAM BOILER
RELIEF VALVE, WATER HEATER
RELIEF VALVE, WATER TANK
REPAIR BURST LEAKY PIPES
METHANE GAS HAZARDS
SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SHUTOFF VALVE LOCATION, USE
SULPHUR & SEWER GAS SMELL SOURCES
SWEATING (CONDENSATION) on PIPES, TANKS
TOILETS, INSPECT, INSTALL, REPAIR
WATER, WELLS, WATER TANKS: TESTING GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMPS & TANKS
WATER SOFTENERS & CONDITIONERS
WATER SOURCE ALTERNATIVES
WATER SUPPLY & DRAIN PIPING
WATER SHUTOFF VALVE LOCATION, USE
WATER SHUTOFF VALVE, WELL PUMP
WATER TESTS, CONTAMINANTS, TREATMENT
WELLS CISTERNS & SPRINGS
WINTERIZE A BUILDING
This article defines tundish and explains where and why a tun dish may be installed on a water heater cylinder, geyser, heating boiler or other pressurized tanks. We include a history of the term tundish and an explanation of the health and safety applications of tun dish use. We describe all of the locations where a tundish is used, including some you may have already seen but didn't think to call by that term.
Our page top illustration of a side-inlet tun dish shows the water flow pathway (red arrows) and the air gap (blue arrow) in a 3/4" tun dish produced by McAlpine Plumbing Products (citation below).
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What is a Tundish & Why, How & Where are they Used: water cylinder, geyser, heater TP valve safety devices
A tundish, or tun dish in some countries, is a fitting installed on overflow pipes to provide an air-gap and a visual window into the flow of water that may pass through the overflow pipe system. The purposes of the tundish are principally to prevent an unsanitary cross connection between an overflow or discharge pipe and a sewer line or drain.
[Click to enlarge any image]
Shown at left is a vertical Tun Dish produced by Ariston (citation below). Our arrows show the water pathway and the air gap that prevents unsanitary cross-connections between potable water and building drainage piping (CROSS CONNECTIONS, PLUMBING).
A secondary benefit of a tundish when installed on a pressure or pressure/temperature relief valve and discharge tube is to provide a visual indication that water is flowing in the overflow pipe - an important safety observation where the discharge tube is piped to a termination that is not visible.
In our adapted illustrations above, the air gap (blue arrow) permits observation that water is flowing through the device. If for example a tun dish is installed on the discharge tube of a water heater cylinder, geyser, or hot water tank, and should that valve open - indicating an unsafe condition as well as attempting to avoid a catastrophe - the building occupants can both hear and observe that water flow.
A tundish is basically a funnel. The origin of the term Tundish is from the brewing industry where casks or tuns were filled from the outlet of the brewing facility by routing the brew through a pipe that discharged over a funnel, originally a shallow wooden dish with an outlet channel that directed the brew into the inside of the tun or cask. The term tundish as a plumbing component is currently used to describe any funnel or hopper that is fed by an outlet pipe and that directs a liquid flow somewhere. - Wikipedia (2014)
Watch out: the use of a tundish may be required or even prohibited by local codes and where used is regulated by building codes such as section G3 in the U.K. as are requirements for temperature & pressure relief valves, relief valve discharge piping, and cylinder, geyser or water heater labeling.
Where is the Tun Dish Device Used & Where is it Required by building code?
Our photo (left) illustrates a U.S. installed clothes washing machine drain connection that almost functions as a tundish. In-wall tundish devices are provided by Britex - in our product source list given below.
Watch out: a tundish or other air gap device can be a source of sewer gas entry into a building. The connection shown at left was indeed asserted to be the source of sewer odors in that home.
Watch out: some service providers or communities do not permit discharge of air conditioner waste to the main sewer line out of concern for the volume of water discharged.
Watch out: as noted in our New Zealand references below, the choice of materials for handling hot water discharge must take the water temperature into account.
Building & Plumbing codes citing the tundish
Other Safety Controls on Water Heating Equipment besides the TunDish
In the U.K. an un-vented cylinder (water heater) and similarly in the U.S., Canada, Australia, New Zealand, and in the E. U., must be protected by at least the following three devices
The purpose of these safety controls is to prevent dangerous BLEVE EXPLOSIONS as water under pressure in a heated cylinder flashes to steam in a tremendous release of energy should the cylinder or tank rupture.
Gas fired heating equipment requires additional combustion-related safety controls such as gas spill sensors and oil fired heating equipment requires corresponding safety devices that monitor the condition of the oil burner.
Tundish Installation Details
By far the most complete detailed advice on proper installation of a tundish for water heating equipment that we have found to date is provided by Main, a U.K. heating equipment manufacturer cited just below. Scotland, Mandatory Standard 4.9.4 also describes tundish installation specifications.
Watch out: These excerpts adapted from Main's advice for tundish installation provides useful information. But be sure to check with the tundish installation requirements in your model and local building codes as well as the installation details supplied by your equipment manufacturer and by the tun dish manufacturer.
"Unvented Mains Pressure Water Heaters 120, 150, 170, 210, 250 And 300 Litre Capacity Indirect Models And 170 & 210 Litre Capacity Direct Models Installation And Servicing Instructions", Main Heating Ltd., Brooks House, Coventry Road, Warwick CV34 4LL, Tel: 0844 871 1532, 36005994 Issue 06, Website: http://www.mainheating.co.uk, retrieved 5/21/2014, original source: http://www.mainheating.co.uk/docs/Main_Unvented_Cylinders_Fitting_Instructions_36005994_issue_06.pdf
Where to buy a Tundish
In Australia, New Zealand, U.K.
Suggested citation for this web page
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