I have some 12 V garden lighting and pond pumps all of which are run through 12v transformers with wiring that shows it had been extended. The wiring was put in place some years ago and the person who did it used what I will describe as "Block connectors" to connect the wire extensions wrapping them waterproof tape which was then buried. When I was re-routing the wiring I found that to put it mildly, the block connectors had deterioted. Is there a waterproof device that one can use that could be used to connect these wires placing it under about six inches of soil?
There are many ways to make water proof connections. Most involve removing the air as expansion and contraction of air tends to draw in moisture.
With both extra low voltage (below 50vac) and low voltage (below 1000vac) there are tried and tested methods like epoxy resin lined shrink sleeve and resin filled plastic boxes sold as cable joints. These should have crimped connectors inside as of course not re-enterable so has to be maintain free.
However even the block connector once encapsulated in resin can't really work loose. Careful use of self-amalgamating tape of even denso tape can keep items dry for years but it is rather hit and miss and both the amount of water and temperature will have a marked change in the life of the joint.
But under the ground the main type of cable used is steel wired armoured and steel will rust if not protected. So although there may be cheap options that will work with ELV cable often to stop rusting underground a proper cable joint will be used.
But one problem is the cost so likely it will be cheaper to run new cables than buy the cable joints. Any so called water proof connector will underground leak, but using petroleum jelly I have found reduces the number which leak. Not grease as it can contain things which conduct use petroleum jelly.
What you have to consider it only 12 volt so unlikely to injure anyone and last lot did last for years. So is it really would spending loads of money on proper joints. I have used standard shrink sleeve as squirted up a little silicon sealant before shrinking. This will in time go hard and stop water and cost effective for 12 volt.
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