Municipal Well Water Destroying plumbing fixtures

I'm not an electrician and have only a passing knowledge of grounding from my experience as a mechanical engineer. Certainly not the experience needed to give you good specific recommendations. Poor connections in the grounding circuits of any water using appliance can send stray electrical currents into the water system either via the metal pipes themselves or the water if the minerals in it give it high conductivity.

Here's another possibility: Only certain mineral ions in water contribute to hardness. I don't think common salt, sodium chloride, is part of the measure for water hardness(IIRC). But chlorides are highly corrosive to metals. They also substantially increase the electrical conductivity of the water, which would facilitate an electrolysis problem if that is what you have.

You could also be having simple local electrolysis from dissimilar metals used in the plumbing acting together with highly conductive water as a battery. A common type of plumbing fitting is an insulating pipe union used in such situations where brass and zinc galvanized steel pipes or components like valves are connected together. The advice of a plumber with experience in local codes and water conditions may be helpful here.

You don't say where you live. In many parts of the world salt water intrusion from ocean waters into overdrawn municipal water sources is a common occurrence. We have this problem in parts of California. But generally the folks that manage water systems stay on top of this issue. And if that is the case in your situation there are probably complaints about the taste of the water and perhaps lesser corrosion issues from your neighbors.

In general I'd be skeptical of any offers to sell you expensive water treatment equipment. It's real easy to throw your money away on such approaches. There is a lot of genuine expertise that goes into selecting the right water treatment methods for unusual domestic water supply problems. I've been down that road with my rural home and it's wells.

Ed Weldon

I would first ask the municipal water company to provide more detail chemical analysis. You should ask for enough info to calculate Langlier's Index or LI. This index is based on Ca as CaCO3 (usually), Alkalinity as CaCO3, pH, Total Dissolved Solids mg/L (or ppm), and temperature (Usually in degrees Celcius but can be calculated from Fahrenheit). You should calculate the index at many temperatures. Google Langlier index and you will find a host of sites to help you. It is also likely that the water company has similar complaints on file and may have ready answers for your problem.

As your water comes from a well you should expect fairly stabilized raw water temperature (at or near the ambient year round air temperature) and a fairly stabilized LI. However, you mentioned you are using a tankless water heater and that suggests a high variance in water temperature ( from background well temperature to near boiling temperature on the hot water side).As the water heats the ability of the water to hold calcium in solution drops and results in scaling. This scaling then can lead to galvanic corrosion. Galvanic corrosion occurs where dissimilar metals will create a small battery cell action and minerals will migrate from from an anode to a cathode with the well water acting as the bridge between. So minerals deposited by heating the water can create the galvanic cell. Generally, cold water has higher corrosive capability and hat water has higher scale forming capability.

If the corrosion is occurring on the cold water taps you can either have a very low LI or their may even be other minerals such as iron depositing inside the pipes and again setting up a galvanic cell.

Galvanic cell is the likely culpert in your corrosion of plumbing. A few things to help you would be to use dielectric unions to connect point of use HW systems. If you use dielectric unions you will need to bridge the grounding connections used for houshold grounding (check local electric codes). A second method to help reduce the corrosion is to add a coating to the plumbing such as polyphosphate. The polyphosphate will help to sequester (keep in solution) metals such as iron and manganese. Polyphosphate or PP will also create a thin molecular coating on the piping that is protective as long as you maintain the system or cartridges that provide the PP. You can purchase cartridges to install in line that contain PP at a relatively cheap cost but would have to be replaced every couple of months or so. Softening the water (particularly the water entering the hot water system) will also help.

Good Luck

You should also ask the water company how they chlorinate the water, either continuous injection or batch addition. In batch addition a large amount of ClO₂ is added to the treated water at regular intervals. Batch treatment often results in erratic pH levels in the distribution system. The end result is a cycle where a high or low pH will strip the oxide layer from the inside of the pipe. When the pH returns to normal, the layer is rebuilt by corroding the inside of the pipe. Then the pH goes out of whack again, stripping the new layer. The cycle repeats until the pipe fails. This type of problem is usually evidenced by small pinholes in the middle of a solid piece of pipe.