Oil slick on tank while water testing

[ScottD]

I’ve started filling my tank with RODI water to leak test it and planned to mix salt in afterwards. While filling it up I’ve noticed an oil slick on the surface of the water. I’ve been skimming water off the surface to try and get rid of it and it’s helped, but there is still some there. Is it something to be concerned with?

 

[Dom]

Yes. I'd want to identify the source of the oil. A layer of oil on the surface with impede gas exchange between the room air and the tank.

What did you use to clean the tank?

 

[Mr. Mojo Rising]

Did you add anything to the water? If not, then it might concern me, I would probably empty it and clean it out.

I know you don't want to hear it, but I'll be 'that guy' and say it anyways lol - that's why you use tap water for the leak test. Cheers - at least its Friday

 

[thedon986]

Looks like powder from filling up the first time with dry rock and sand. Expected. Make sure your filtration has a surface skimming component.

 

[ScottD]

Yes. I'd want to identify the source of the oil. A layer of oil on the surface with impede gas exchange between the room air and the tank.

What did you use to clean the tank?

I used vinegar to clean the tank before putting anything into it.

 

[ScottD]

Did you add anything to the water? If not, then it might concern me, I would probably empty it and clean it out.

I know you don't want to hear it, but I'll be 'that guy' and say it anyways lol - that's why you use tap water for the leak test. Cheers - at least its Friday

I put my rock in and filled with rodi water is all, nothing else added. I’m not worried about wasting rodi water if I need to empty it and start over. I wasn’t over concerned about it leaking, so that’s why I filled with rodi and not tap water.

 

[Sumbub]

@thedon986 is right. It looks like fine particulates to me.

 

[ScottD]

Looks like powder from filling up the first time with dry rock and sand. Expected. Make sure your filtration has a surface skimming component.

At first it seemed like more powdery stuff but once I got that out, it’s been an oil slick. The tank has an overflow so that will skim the surface but haven’t filled the tank enough for it to drain into the sump as I wanted to minimize contamination if it is contaminated.

 

[Sumbub]

At first it seemed like more powdery stuff but once I got that out, it’s been an oil slick. The tank has an overflow so that will skim the surface but haven’t filled the tank enough for it to drain into the sump as I wanted to minimize contamination if it is contaminated.

You could use plastic wrap/cling wrap and touch the water surface to remove it.

 

[ScottD]

You could use plastic wrap/cling wrap and touch the water surface to remove it.

So just lay it on top of the surface and let it stick to the cling wrap?

I was considering trying something like this:

https://a.co/d/fiaGTub

 

[Sumbub]

So just lay it on top of the surface and let it stick to the cling wrap?

I was considering trying something like this:

https://a.co/d/fiaGTub

The oil will cling naturally to the plastic. They do this in cooking when they need to get oil off the surface of the water/soup. Just lay it gently on top then pull upward. Should get most of it.

I'm not sure about the pads. I feel like it should be for spilling onto it?

 

[ScottD]

The oil will cling naturally to the plastic. They do this in cooking when they need to get oil off the surface of the water/soup. Just lay it gently on top then pull upward. Should get most of it.

I'm not sure about the pads. I feel like it should be for spilling onto it?

Thanks I’ll give that a try.

 

[Dom]

I used vinegar to clean the tank before putting anything into it.

Then I would run the pump on the tank and shove some polishing media into the filter media rack to trap it all.

 

[ScottD]

Then I would run the pump on the tank and shove some polishing media into the filter media rack to trap it all.

I was also thinking about putting some gac in a filter sock and running that for a bit too as a precaution, forgot to mention that before.

 

[Dburr1014]

Cling plastic is a good idea, I was going to say use paper towel to float on top.

If you have a sump it'll eventually it will get skimmed right out.

 

[Dom]

I was also thinking about putting some gac in a filter sock and running that for a bit too as a precaution, forgot to mention that before.

Yes, that might be a good idea until you figure out what it is and the source.

I was thinking, to rule out oil, maybe try trapping some of it in a plate. Then, place one drop of Dawn dish washing liquid in the middle. If it scatters, then I would think its oil.

 

[ScottD]

Yes, that might be a good idea until you figure out what it is and the source.

I was thinking, to rule out oil, maybe try trapping some of it in a plate. Then, place one drop of Dawn dish washing liquid in the middle. If it scatters, then I would think it’s oil.

I just did this and it disappeared from the surface.

 

[Dom]

OK!

So I think it’s probable that you’re dealing with an oil slick. Now the question becomes what is the source?

Is it possible that perhaps you had hand cream on your hands when you placed your hands in the tank?

Anyway, I think the best thing to do is to filter it out as best as you can.

If it returns, then the source is probably somewhere in your equipment. If it doesn’t return, then it was probably something on your hands.

 

[ScottD]

I don’t usually use hand cremes but maybe something was on them from work or something. I tested with a piece of cling wrap and it seemed to work so now going full scale with it.

 

[Dom]

I don’t usually use hand cremes but maybe something was on them from work or something. I tested with a piece of cling wrap and it seemed to work so now going full scale with it.

Interesting. Keep us posted.