High zinc level from well drop pipe

[Mark1061]

Four years ago I had an 860 ft deep well drilled in western north Carolina. Last year they installed a galvanized drop pipe and pump about 800 ft down. The county water test showed high zinc at 20mg/litre (should be less than 5) but everything else including lead was normal. pH is neutral. I have done several tests and samples have always been taken at the well head. The water tastes like zinc lozenges for colds do, kind of astringent.

I have checked with the County and they say they never see high zinc. I have also checked with the State department that oversees water quality and their opinion is it must be coming from the drop pipe and maybe stray electricity may be involved. The steel casing is bonded to the drop pipe and the driller says that is connected to the 3 wire pump.

The driller is suggesting schedule 1 1/4" 120 pvc to 650 feet to replace the metal pip but I am nervous as his experience is mainly with galvanized. I'd like to check out stray electricity first to save changing the pipe but neither my builder or the driller know how to do this.

How would I go about testing for stray voltage? Thanks for any help anyone can give me.

 

[Valveman]

Stray voltage is very possible if you have one of those Variable Speed Pumps? I know of one variable speed pump that was hung on PVC pipe, but had a galvanized bushing going into the pump. In a matter of a few months the galvanized bushing had completely dissolved. The lady in the house got very ill, and they are pretty sure it was from drinking the dissolved galvanized bushing.

If you do not have a variable speed pump, then I have only seen stray voltage one time when a water heater was not properly grounded. This actually caused multiple holes in the copper pipe throughout the house.

 

[Sponsor]

 

[Mark1061]

Stray voltage is very possible if you have one of those Variable Speed Pumps? I know of one variable speed pump that was hung on PVC pipe, but had a galvanized bushing going into the pump. In a matter of a few months the galvanized bushing had completely dissolved. The lady in the house got very ill, and they are pretty sure it was from drinking the dissolved galvanized bushing.

If you do not have a variable speed pump, then I have only seen stray voltage one time when a water heater was not properly grounded. This actually caused multiple holes in the copper pipe throughout the house.

Thanks for your reply. The pump is a Grundfos 5S15-31 81545315 4", I don't think that one is variable speed.

 

[Reach4]

I'd like to check out stray electricity first to save changing the pipe but neither my builder or the driller know how to do this.

I don't know if it would be effective, but it would be easy to see if there is current in the green wire to the pump. I would expect near zero. I don't know how near.

 

[Valveman]

There is an entire industry in stray voltage. I think it can also come from fluorescent lighting. It is a big problem in Dairies. Cows feel a 4V shock when they take a drink of water, so they don't drink. Milk is just water processed through a cow, so no drinky, no milky.

 

[LLigetfa]

It is a big problem in Dairies.

The disparate ground potential in those cases are usually due to long service wires between buildings and inadequate bonding of protection grounds. I have experienced so much ground current where a service was only bonded to a water pipe that it warmed the water in the pipe.

When I built my home, the electrical inspector would not sign off until I ran a bond wire from my protection ground to my well casing. I was concerned that my well would be a conduit for stray ground current from my neighbors. I tried arguing with the inspector to the point where I asked him to show me where in the code it was a requirement. I even asked "what if my well casing was PVC?". He could not provide a code reference, but still would not sign off until I bonded to the casing.

 

[Mark1061]

I don't know if it would be effective, but it would be easy to see if there is current in the green wire to the pump. I would expect near zero. I don't know how near.

How would I do this, one multimeter probe on the pump green and the other test lead would go where? Thanks.

 

[Reach4]

You would put the clamp around the single wire.

 

[Valveman]

I think the amperage would be very small and hard to detect. I would think you should be looking for 1 to 4 volts between the pipe and a ground.

 

[Craigpump]

We run 1" sch80 PVC to 680' with sch120 PVC couplings all the time with no issues.

 

[Mark1061]

I think the amperage would be very small and hard to detect. I would think you should be looking for 1 to 4 volts between the pipe and a ground.

Yep, I get 5 volts from the plate that supports the pipe to the service ground rods. I would have thought the pipe would have been grounded through the pump motor if only because it is physically connected. If I bond the pipe to the service ground would that possibly solve the zinc problem?

 

[Mark1061]

We run 1" sch80 PVC to 680' with sch120 PVC couplings all the time with no issues.

Do you use a length of stainless pipe either at the top or the bottom? I have read it is good to use one stick of ss pipe to connect to the pump to protect the drop pipe from starting torque.

 

[Craigpump]

No, sch 80 all the way. You should find out why you have stray current and fix that, maybe your problem will go away. No way to tell how much damage has been done to galvanizing on the pipe though.

 

[Valveman]

Do you use a length of stainless pipe either at the top or the bottom? I have read it is good to use one stick of ss pipe to connect to the pump to protect the drop pipe from starting torque.

You don't need SS pipe or torque arrestors if you don't let the pump cycle on/off too much. With only a 5 GPM pump I would fill a 1000-2500 gallon cistern storage tank. That way the pump only has to run like one time per day to fill the cistern. Then you could have a 20 GPM pump in the cistern pumping to the house. This gives you a lot more water available to the house and keeps the well pump from cycling.