Can you see chlorine bubbles?

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
4,694
Damascus, MD
The other day I had some small bubbles coming out of my returns in the pool. I had the SWG on but had the flow pretty low probably 1000 rpms. Was I seeing the chlorine gas?
 

domct203

Bronze Supporter
LifeTime Supporter
TFP Guide
Jun 3, 2015
3,959
CT
I would think yes. I can see small bubbles coming out of my returns when my SWG is running.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,964
Tucson, AZ
It depends. Most bubbles coming out are hydrogen gas NOT chlorine. Chlorine gas is highly soluble in water. Only in a short pipe run from the SWG to the pool can you get chlorine gas evolution. In that case, the pH of the pool will go up very fast.

In general, the answer is no.
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
4,694
Damascus, MD
It depends. Most bubbles coming out are hydrogen gas NOT chlorine. Chlorine gas is highly soluble in water. Only in a short pipe run from the SWG to the pool can you get chlorine gas evolution. In that case, the pH of the pool will go up very fast.

In general, the answer is no.
How can I tell? Light the bubbles?
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,964
Tucson, AZ
How can I tell? Light the bubbles?
Yes. If you hold a lit cigarette lighter over the bubble stream close to the water you might hear a slight popping sound. You could also collect the bubbles in a plastic tube.

But it's really unnecessary. It's not chlorine gas. If it were, you'd choke from the smell as chlorine has a very low odor threshold and induces coughing and reflexive gagging pretty quickly. As I said, chlorine gas has very high solubility in water and is almost totally absorbed by the water at the SWG plates. One would need the SWG output set to 100% and a very short pipe to capture chlorine gas. This is why running an SWG with no flow can cause an SWG to explode - the hydrogen and chlorine buildup very quickly and form concentrated gas pockets. H2/Cl2 gas mixtures are highly explosive and easily detonated (shock, electricity, blue light, sparks, etc).

As JamesW has said, it's hydrogen.