Tempering valves are required to be installed in the following situations (in accordance with the Plumbing Code of Australia):

The way I read it is that Dyelectric fittings are not to be used becase the SAME type of pipe is required throughout. Correct?

The corrosive product often fills the pipe diameter restricting the water flow and is often the source of rusty water. Our company does not promote the use of dielectric unions, because they do not effect the corrosion characteristics of the water heater. Due to our cathodic protection system, the juncture of the supply piping and the tank fitting is adequately protected by the cathodic protection system against corrosion without the buildups which occur in the dielectric union.

A dielectric union is designed to break the electrical contact between two dissimilar metals (to prevent galvanic corrosion). Most of the flexible copper connector hoses on water heaters have a plastic washer that acts as a dielectric union.

Dielectric unions may have been used many years ago and were installed with the thought to assist in reduction of corrosion that could develop at the piping connections. From time to time, this inquiry is brought to our attention stating the use of dielectric unions may be suggested required or should be, perhaps used.

The installation of unions on the inlet and the outlet waterlines and a shut-off valve in at least the cold inlet waterline is recommended, so the water heater may be easily disconnected for servicing.

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A dielectric union is designed to break the electrical contact between two dissimilar metals (to prevent galvanic corrosion). Most of the flexible copper connector hoses on water heaters have a plastic washer that acts as a dielectric union.

When there is a concern with using dielectrics, a plastic lined nipple have the ends of the plastic fold over the end of the nipple which provided an excellent dielectric. The plastic engages the thread of the fitting a attached, whether it be the tank of the piping, thereby insulating the metal nipple from the water. This prevents corrosion on either part. These nipples have been certified as dielectrics in numerous areas of the United States.

The corroded, leaking dielectric union in the back was installed by a ‘licenced plumber’. I installed the copper tube/hose and fittings. I paid quite a bit more for the brass fittings, I guess that is why people like the galvanized steel ones (cheap).

TMVs are generally used in environments that include high-risk persons, such as children, the elderly and the sick, that require a lower water delivery temperature (usually 45°C or 113°C as a maximum).

If you have any further questions regarding tempering valves, TMVs or other hot water arrangements, give Brisbane Plumbing and Drainage a call on 1300 616 203 and we would be happy to discuss your hot water needs.

I did not look at the picture on your post earlier. the nipple on the cold water connection in the photo is shipped by the water heater mfg that are delivered to plumbing suppliers and are used to prevent a galvanic reaction. Because the fittings add about $5.00 to the cost of the heater retail stores such as Home depot buy their heaters with out the nipples. Most of the problems occur when water heaters are installed by homeowners that do not know any better or by the plumber that works out of the back of his truck

The way I read it is that Dyelectric fittings are not to be used becase the SAME type of pipe is required throughout. Correct?

A tempering valve is a temperature-sensitive 2-inlet or 3-inlet mixing valve which pulls water from your hot water system, mixes it with cold water and delivers it to a faucet. General household use requires hot water to be no hotter than 60°C, however, appliances such as dishwashers and washing machines may have differing settings.

Visual inspection means just that. If you were unscrewing plumbing to check for missing parts , you, would have worse problems than lack of a proper dielectric union.

Tempering valves are generally used in residential homes for personal hygiene purposes, where water delivery is a maximum of 50°C (122°F)

The way I read it is that Dyelectric fittings are not to be used becase the SAME type of pipe is required throughout. Correct?

You can typically see part of the plastic washer/flange sticking out at the top of the fitting. This plastic fitting is frequently damaged when the fitting is tightened too much, causing a loss of the dielectric properties.

Tempering valves are adjustable and temperature-activated, meaning they moderate hot water flow when necessary to ensure water isn’t too hot when it is delivered to a tap. Hot water that is stored in a hot water storage system should be kept at a temperature of at least 60°C, however, water should be delivered through a faucet at a maximum of 50°C. A tempering valve works by blending hot water with cold water so it flows through your tap at the correct temperature, within 3°C +/-.

A TMV works by mixing hot and cold water together to achieve a particular temperature (within 1°C +/-) to be delivered in various. The temperature is usually preset by a plumber or a qualified tradesperson who has installed the device, and the element within a TMV that is sensitive to thermal activity automatically arranges the appropriate levels of hot/cold water to create the correct temperature of the liquid.

Probably better for the TX SOP to call out actual corrosion rather than all of the dielectric / non-dielectric scenarios or we’ll wind up with another SOP standard as silly and confusing to the public as the no AFCI defects in older homes.

For two reasons – for safety and in accordance with the regulations. For the safety of those using a tap and to avoid injuries such as scalding, a tempering valve or TMV ensures the water being released from the faucet is not above 60°C (140°F) for tempering valves or 45°C (113°F) for TMVs. Additionally, in accordance with Australian regulations (National Plumbing and Drainage Standard AS/NZS 3500.4: 2003), various water installations are not permitted to deliver water at a temperature higher than 60°C/45°C for different fixtures.

When you turn the tap on in your home or workplace, you expect water at the correct temperature to be delivered – whether that be hot, cold, warm or something in between.

I’ve attached and old tech bulleting from Rheem on the topic. I’m not sure if it’s still accessible on their site. Also note that the nipples on top of the water heater are supposed to be dielectric, but as far as I know you can’t tell visually once the plumbing is hooked up.

A thermostatic mixing valve, or TMV, is a great little gadget that blends both hot and cold water together to achieve a particular, predetermined water temperature when delivering water through a faucet.

The theory that is in practice is described as follows: All metals when immersed in an electrolyte, such as water, have a voltage potential. This voltage potential varies from approximately +3.0 volts to a –3.0 volts. The relative activity of the metal is determined by voltage potential with those metals with negative voltages being most active and more likely to corrode. Magnesium, for instance, has a slightly negative voltage, approximately –2.0 volts, and will corrode very rapidly in certain waters. Iron has a voltage potential of –0.4 volts and rusts (corrodes) very rapidly when exposed to a moist atmosphere. Copper on the other hand has a voltage potential of +0.350

Ya I thought of that. Seems like the water heater would fail before serious dielectric corrosion. They only last 6 to 10 years here.

The wonderful little device that helps achieve the right hot water temperature is either a tempering valve or a thermostatic mixing valve, which can easily be mixed up but are actually two different things. To help you decipher between the two and figure out which one is best for your needs, take a read of the below information or give Brisbane Plumbing and Drainage a call on 1300 616 203 and we would be happy to assist.

A qualified plumber can install a tempering valve, however, a plumber with a TMV licence is the only one who can install a thermostatic mixing valve.

Any metal with a negative voltage when coupled with a metal with a more positive voltage potential will sacrifice (corrode) itself to protect the metal with more positive (noble) voltage. By placing a dielectric (insulating) fitting between two dissimilar metals, i.e. iron and copper, there is a break between the two. Therefore, in theory the iron will not corrode to protect the copper. In fact, the circuit is generally completed through the water, and depending on the water conductivity the iron will corrode at various rates.

I hear ya. All you can do is your best. Kinda like how in Illinois we observe the plumbing which is worded differently from the other systems that we are required to inspect. Everyone says it is because of the plumbing union , but my opinion is it also has to do with not unscrewing and turning shutoff’s. Plumbing is like that as we all know.

This means that all hot water system replacements should have a tempering valve installed. Some hot water system repairs do not require a tempering valve to be installed, but we suggest speaking to your plumber anyway to see if this is an option (it should be!).

TECHNICAL SERVICE DEPARTMENT Technical Service Bulletin 1-800-432-8373 Dielectric Technical Competence, Product Confidence Page 1 of 1 1221.doc Dielectric – an electricity, especially a substance with electrical conductivity less than a millionth (10 to the –6) of an MHO.

IMO Dielectric unions have very limited benefit as the water within the pipe also conducts current, effectively defeating the “isolation” provided by the dielectric device. I see corroded nipples and fittings on and around water heaters all the time, regardless of whether dielectric isolated unions, couplings, connectors, etc. are used. Sometimes it’s caused by the copper flex connector with the integral isolator itself. Brass seems to have more universal compatibility, which is why I prefer to see brass nipples.

The required use of dielectric unions on our water heaters is not necessary. With this in mind, uniformity of piping material must be administered by the installer. What is meant by this is “the piping used in the system i.e.: copper, etc. must be the same throughout, to and from the water heater”. When different piping material connectors are used, corrosion can be immediate and will commence deterioration within days of installation Why is this? When two or more different metallic piping materials are used there can be some level of electrical current flow between the materials due to their different levels of electrical voltage potential. By uniformly using the same material to pipe the water heater, there is essentially no difference in electrical potential between the piping and the water heater tank. Therefore, dielectric fittings are not required when following the uniformity of piping material.