Skimmer ?'s

What is the difference if any between an in sump skimmer and a recirculating skimmer?

 

by recirculating, do you mean a hang on the back of tank style skimmer?

 

No that would be a HOB or HOT skimmer depending on who you buy from. I am talking a skimmer that is under the tank.

 

A recirculating skimmer has a pump that does not pump water in or out of the skimmer - It takes water from already inside the skimmer, adds air and creates bubbles (At least this is my understanding). An in sump skimmer has a pump that creates bubbles as it pushes water into the skimmer.

 

In-sump refers to where its situated. In sump, external, or hang on. All refers to placement.

Recirulation refers to water pumping. A non-recirculating skimmer pulls water from the sump, circulates it and drains back into the sump. A recirculating skimmer typically has two (or more) pumps. 1 pump pumps water into the skimmer and drains it but with no air. the second (or more) pumps draw water from within the skimmer, add air, and "recirculate it" through the skimmer body, hence its name.

 

So can I just gravity feed the skimmer from the second overflow and then have the extra water go into the sump to be returned via the return pump. Or do I have to have a second pump to push the water in/out of the skimmer etc. Not sure on the plumbing for this. I know how I am plumbing the sump but this was suggested by a fellow reefer and no mention of the plumbing.

 

You can feed it from the overflow/drain but that isn't the best option. When you feed it from the drain from the display, you are going to get a surging water level. Its just the nature of the overflow. Its going to speed up and slow down. That causes fluctuating water level in the skimmer and thats bad for the skimming. I have seen setups where the drain had a T in it with a valve under the T. The T adjusted water flow to the skimmer, the other side of the T drained into the sump.
The other major problem with feeding the skimmer from the drain is trying to take the skimmer offline. Just more work than its worth unless you have the room to do it.

The best option is simply to have a pump feed the skimmer. Then the flow is constant and you don't have to worry about it. Makes it simply to take the skimmer off line.

 

would it work If I placed a gate valve in the tubing from the drain to the skimmer?

 

Thats the "valve method" of feeding. Put a T above the gate valve. The side of the T not going to the gate valve will simply drain into the sump. As long as the gate valve is closed enough to always push water out the side of the T, there should never be air in the gate valve side and you should always have a constant flow to the skimmer. If the flow coming out of the side of the T into the sump fluctuates it won't matter, the flow to the skimmer will be constant.

I would put a union coupling after the gate valve. Then if you ever need to disconnect the skimmer for any reason, you can shut off the gate valve, undo the true union coupling, remove the skimmer, and put it back without having to shut the system down.