Home made swimming pool heat pump

[frank]

I would have agreed with you some years back, but the truth is, there is really no problem at all with Chlorine treatment of pools and copper. However, strangely as it seems, if the pool operator doesn't keep the chlorine level right, ie high enough, then there would be a problem with corrosion. The Chlorine oxidises organic material in the pool, if there is insufficient free Chlorine then Chloramines are produced. It's these Chloramines that give the "chlorine" smell in pools and also causes sore eyes.

Children are a common factor here!

So when you smell chlorine in a pool hall it indicates the treament is off or not being kept up to adequate levels to combat the chidren

Some years back, a friend asked me to have alook at his fathers pool heater.

A basic set up with a condensing unit, maybe 1hp, situated within his large green house and a stainless steel cylinder with copper discharge pipework coil running through it. It looked like a home made jobby.

When I connected my gauges on the suction rotolock, water came out

When It was stripped in our workshop, the discharge copper coil was disintegrating,

I managed to replace it, dry out the existing condenser, rebuild it and re-install it back into his greenhouse. It's still going strong

I used 316 S/S tubing though, not copper in the re-build.

I haven't worked on any S & T HX's for pools since, only brazed plate HX's

[Gary]

Some years back, a friend asked me to have alook at his fathers pool heater.

A basic set up with a condensing unit, maybe 1hp, situated within his large green house and a stainless steel cylinder with copper discharge pipework coil running through it. It looked like a home made jobby.

When I connected my gauges on the suction rotolock, water came out

When It was stripped in our workshop, the discharge copper coil was disintegrating,

I managed to replace it, dry out the existing condenser, rebuild it and re-install it back into his greenhouse. It's still going strong

I used 316 S/S tubing though, not copper in the re-build.

I haven't worked on any S & T HX's for pools since, only brazed plate HX's

I'm wondering if the corrosion might have been the result of using dissimilar metals.

[Acuario]

I'm wondering if the corrosion might have been the result of using dissimilar metals.

Sounds like it to me - according to nobility table stainless steel is quite anodic and far away from copper which is cathodic with the result being that the copper will corrode.

[nevgee]

Sounds like it to me - according to nobility table stainless steel is quite anodic and far away from copper which is cathodic with the result being that the copper will corrode.

There is always that possibility but the majority of corrosion in swim pool apps is not due to electrolytic wasting but chemical reaction. That's why it is essential the chemical balance of the water is kept spot on.

[frank]

I'm wondering if the corrosion might have been the result of using dissimilar metals.

The corrosion was not at the point where the copper entered the s/s cylinder. It was the majority of the coil within the cylinder which was in constant contact with the circulating chlorine water.

[Acuario]

I've seen this happen with copper cold water pipes that were connected to galvanized iron fittings. I went into a customers garage and there was a fine mist of water being sprayed from the numetous micro perforations in the pipe. How it hadn't burst I'll never know. The whole length was pretty much the same. Water conducts electricity.

Also, years ago my dad worked for the gas company in the UK. In the late 60's/early 70's there was a shortage of copper pipe so they decided to install central heating with steel pipe. Total disaster, it all had to be ripped out and replaced due to electrolysis destroying the steel pipe.

[nevgee]

Some years back, a friend asked me to have alook at his fathers pool heater.

A basic set up with a condensing unit, maybe 1hp, situated within his large green house and a stainless steel cylinder with copper discharge pipework coil running through it. It looked like a home made jobby.

When I connected my gauges on the suction rotolock, water came out

When It was stripped in our workshop, the discharge copper coil was disintegrating,

I managed to replace it, dry out the existing condenser, rebuild it and re-install it back into his greenhouse. It's still going strong

I used 316 S/S tubing though, not copper in the re-build.

I haven't worked on any S & T HX's for pools since, only brazed plate HX's

I have come across many situations simillar to that you mention. We find if we test the water the PH tends to be down below 0.7. At this level the water leeches all metal components. In some cases I've had to return and redo the whole wash out within months of the first repair. One guy was an industrial chemist and thought checking his water 6 monthly would be adequate? every week is essential at the min.

I find worse case is when there are lots of children using the pool for other than swimming. Air born Chloramines rot all the metal work, stainless as well.

[nevgee]

I have come across many situations simillar to that you mention. We find if we test the water the PH tends to be down below 0.7. At this level the water leeches all metal components. In some cases I've had to return and redo the whole wash out within months of the first repair. .

Sorry for my error ..... should have read 7.0 not 0.7.

The ph of a swimpool water should ideally be 7.4