Equipotential bonding

[Freegs]

Hi, Can someone enlighten me.. why am I getting 0.01 MOhms on pipework with mdpe incomer?

 

[VoltagexV]

That reading of 0.01 megaohms is 10 kiloohms, which is a relatively low resistance. You're seeing this because even with an MDPE plastic incomer, the internal metal pipework is still likely being earthed by other paths, like the boiler or central heating system which has its own protective conductor. The 10 kiloohms reading is the total resistance back to the main earthing terminal through all those parallel earth paths in your home, which is completely normal. You must still main bond the pipework because it remains an extraneous conductive part that needs to be part of the equipotential zone, regardless of what your meter shows.

 

[electr0roy]

Hi, Can someone enlighten me.. why am I getting 0.01 MOhms on pipework with mdpe incomer?

It's all about the 'Fortuitous Earth.' That low reading means your pipework is connected to the ground/earth somehow, but not through the MDPE. It's called a 'fortuitous connection'

 

[PGB1]

Hi Freegs,
In addition to the good information provided by VoltageX and elect0roy, the dissolved ions & other impurities in the water inside the MDPE will conduct electrons to earth.

Non-Conductive tubing, such as MDPE, won't stop electron flow once water is inside it.
One path is the water in the tubing goes to something well grounded. It could be the city water main (malleable iron usually), the curb stop (brass), the corporation stop (brass) or a lead service line. The "other end" of that water is also connected to something grounded in the house- boiler, water heater, etc. Now you have a medium to low impedance path for electrons to flow.

The Dissolved Solids meters we use utilize electron flow to test water. Only 100% pure water shows no conductivity. For those with a meg ohm meter, a fun trick to try is to fill a plastic bowl with tap water & test. Lots of conduction!

Paul