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#2578 07/13/01 03:00 PM
Joined: Jul 2001
Posts: 599
J
JBD Offline OP
Member
One of my customers has an indoor swimming pool. The copper pipes in the pool are being eaten away to the point of failure. Sacrificial copper pieces were placed in the pool and have also corroded. This pool is not plumbed to the house water system. The pool is filled from well system and uses bromine as the base chemical.

All metal parts are grounded and no potential can be measured between any two different metal surfaces. However, there is a +0.5VDC potential between the water surface and the ground grid. It appears that this pool has become a battery.

Any suggestions?

#2579 07/13/01 06:58 PM
Joined: Oct 2000
Posts: 5,392
S
Member
Hi JBD !

so you have a battery created by chemical means, quit the chemicals...?

#2580 07/13/01 08:06 PM
Joined: Feb 2001
Posts: 60
S
Member
That's exactly what a battery is. A big pool giving up electrions.

#2581 07/13/01 09:40 PM
A
Anonymous
Unregistered
The most obvious solution is to eliminate any surfaces of dissimilar metals.

Plating, enameling, painting, replacement with non-metallic, etc., are possibilities.

You can't mix copper and any other metal.
If the pool is aluminum, no metal except aluminum in the pool.
If the pool is steel, no metal except steel in the pool.

Proper grounding can make the corrosion worse!

You could try applying a strong negative bias onto the pool, like -30 V DC. But getting rid of the all but one metal is the only real solution.

#2582 07/14/01 05:07 AM
Joined: Apr 2001
Posts: 21
P
Member
I'd look for too much bromine and/or low pH (acidic) first. If the pool is carbon steel or aluminum with copper piping, the steel/alum are more anodic and would more likely be the victim of galvanic corrosion rather than the copper.

Dsparks, are you aware that the purpose of the bonding grid in a swimming pool is to eliminate voltage gradients. And, if there is water in a swimmers ear, voltage gradients as low as 4V is enough to cause disorientation and drowning. Have you ever seen impressed current cathodic protection or similar used in swimming pools, I am aware of it's use on tanks, pipelines and boats. My gut instinct is to strongly oppose your casual suggestion to toss a charge into the pool and see if it stops the corrosion.

Phil H

#2583 07/14/01 05:13 AM
A
Anonymous
Unregistered
>are you aware that the purpose of the bonding grid in a swimming pool is to eliminate voltage gradients.
Yes, I was just musing that bonding won't stop corrosion.

>Have you ever seen impressed current cathodic protection or similar used in swimming pools, I am aware of it's use on ... boats.
...boats with people swimming around them.

>toss a charge into the pool
I meant to say 'onto' the metal/bonded part, not 'into' the water!

#2584 07/16/01 12:25 PM
Joined: Jul 2001
Posts: 599
J
JBD Offline OP
Member
The pool is a "poly-concrete" construction. The plumbing is copper, PVC, and ABS. The only metal surfaces in the water are: a stainless steel ladder connected to brass fittings (which are bonded), the cast iron drain grates, and the lighting fixtures. This is basically a typical in-ground construction, the only difference is bromine instead of chlorine.

We are checking with water professionals, but we wanted to rule out basic electrical possibilities.

#2585 07/17/01 07:31 PM
Joined: Jul 2001
Posts: 1
M
Junior Member
Copper pipes in pool plumbing and pool heaters usually start to "rott away" and corrode because the ph and alkalinity of the water is very low and the chlorine or bromine is very high. Once the ph gets lower than about 7.4 and the alkalinity gets lower than about 70ppm, the oxidizer (in this case bromine) becomes very reactive.

Most pool pipes and fittings are plastic and this water condition will not adversly affect them - however if copper pipes are used - or if the pool has a heater on it - the copper will start to corrode. I believe this is what is probably happening to this subject pool. I would take a water sample to a local pool store and have them do a complete water test on it.

I predict it will be low ph & alk and high in bromine. I would add a sequestering agent / demineralizer to the water to try to lock up the existing chemical reaction. Then I would adjust the ph & alk a little on the high side (7.8 PH and 150 alk). Then I would adjust the bromine to about 2.0 ppm. This should keep the water relatively odorless, clear and non-corrosive to the pipes.

Quote
Originally posted by JBD:
One of my customers has an indoor swimming pool. The copper pipes in the pool are being eaten away to the point of failure. Sacrificial copper pieces were placed in the pool and have also corroded. This pool is not plumbed to the house water system. The pool is filled from well system and uses bromine as the base chemical.

All metal parts are grounded and no potential can be measured between any two different metal surfaces. However, there is a +0.5VDC potential between the water surface and the ground grid. It appears that this pool has become a battery.

Any suggestions?


#2586 07/17/01 07:47 PM
A
Anonymous
Unregistered
>My gut instinct is to strongly oppose your casual suggestion to toss a charge into the pool
http://dailynews.yahoo.com/h/wjla/20010717/lo/no_charges_to_be_filed_in_lake_electrocution_1.html

#2587 07/17/01 07:55 PM
Joined: Oct 2000
Posts: 4,081
Likes: 3
Member
Moose,

Thanks for the Comments.
Original Name !! [Linked Image] (his dog's name)

I know "Moose" you can visit him at:
http://www.poolandspa.com/
Biggest Pool & Spa site on the net!


Bill

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