0

I have a titanium immersion element in my water tank. It sounds as if it's on it's way out and I'm looking to replace it with another titanium one. How long should it be?

Currently I'm using an 11", but I've seen 14" ones. They are both BEAB approved 2.25 BSP thread and either would fit the size of my tank. They're both 3kW, and there is only a few pounds extra for the longer one. It mounts horizontally.

My thought is that a 14" element will run cooler per unit length. Might it therefore last longer as thermal effects will be less? Am I right, or does experience prove otherwise?

6
  • I assume that the outer envelope of the heating element is titanium but the actual heating coil is some other metal, right? If the power is the same and the length is longer that would suggest longer lifetime. Is the normal failure mode burning through of the heater coil itself or the failure of the outer envelope? As a point of inquiry since I'm in the US, what is the construction of the tank, shape and material? What volume of water does it hold? Is the tank pressurized and operating automatically or is it batch? Jan 13, 2017 at 11:34
  • Failure of the outer envelope from what looks like corrosion, although to be honest I've not yet seen a failed titanium element . This is my first, but from the sounds it's making, I suggest that the outer casing has already been penetrated. You can hear little bangs as the water flash boils inside the element. Probably not long left. The tank is unpressurised copper, about a metre high and operates thermostatically. I take it you're not English then?
    – Paul Uszak
    Jan 13, 2017 at 16:14
  • Is this tank a water heater for your house, or something else? I'm not English, but here in the US, the water heater is plumbed into the water supply system and IS pressurized (because water supply systems must be pressurized in order to get water to go uphill).
    – William S.
    Jan 13, 2017 at 17:03
  • @Paul Uszak I'm American but I have some familiarity with how things are done in Britain. Sounds like a very nice copper tank. Are the joints soldered. Is it high in the structure and delivers by gravity feed or is there a pump? Sounds like you had better get the new element in ASAP. What is the normal lifetime and how long has the current one been in? Jan 13, 2017 at 17:30
  • I have not had a TI element fail. Lower wattage per inch / Cm would reduce the thermal stress on the TI jacket and increase the life. In some equipment I support I will use a higher voltage / wattage element to produce the same heat at lower voltages with well over 3 times the life.
    – Ed Beal
    Jan 14, 2017 at 16:47

2 Answers 2

1

The lower watt density on the longer element will reduce the thermal stress on the heater as long as it will fit. Having a lower watt density should equate to longer life with all other things being equal. Make sure your anode is in good shape when replacing the element for maximum life of the element and the tank. Added:Your heater life may be short because the anode has eroded away. Usually they are attached on the top of the tank a rod that is made out of metal designed to be consumed instead of the tank, heater, and plumbing being erroded. The anode should be checked every few years, I find they usually last ~3 years and many are gone in 5 years. Check the anode and probably replace much cheaper than a new heater, and you just might find your heat rods lasting twice as long or longer.

3
  • Er, what's an anode?
    – Paul Uszak
    Feb 26, 2018 at 17:27
  • 1
    The anode is a rod that is inserted into the tank usually from the top it is a sacrificial material like zinc or combinations of less Nobel metals that are consumed by stray currents. If your anode has failed the heat rods and tank will have a shorter life because the cheap anode material is gone so more expensive metals get eaten away at. Some sediment in the bottom of tanks is from the anode in many cases. Boats have anodes usually zinc blocks attached to the out drive and sometimes to the hull. This protects or reduces damage from dissimilar metals, or galvanic corrosion while in the water
    – Ed Beal
    Feb 26, 2018 at 18:56
  • Ah, no. Most UK cylinders don't have those. We typically have full copper or stainless steel ones. Mine's copper. I think that you'd need a pretty large residence (or commercial premises) to have a plain steel tank + anode.
    – Paul Uszak
    Feb 27, 2018 at 2:26
0

The 14" long heating element may or may not last longer, but it's reasonable to give it a try if the 14" element is from just as reputable a source as the 11" element.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.