Determine the use of the second hole in my skimmer

Oct 10, 2018
6
Canada
#1
I am closing my pool for the first time. I've figured out a good game plan for blowing out the lines, except I am not sure what to do with the second hole in my skimmer.
The second line can be used for 3 things (anyone who uses the first 2 is a moron :hammer: )
#1 A balance line (as per drjames) as was said it's a below water line that "supposedly" keeps the water in the skimmer at the same level as the pool. It's a great idea on paper but the pump is drawing more water than the atmospheric pressure can refill - hence, the skimmer doesn't refill, air is sucked into the line and the damage that this is 'supposed' to prevent happens anyway. (they are also a PITA to winterize!)

#2 Plumb a main drain via the skimmer (as per Jason) - :grrrr: :grrrr: :!: What a moronic idea!!! The valve in the skimmer to control the flow between the skimmer and main drain is highly susceptible to failure and if the main line from the skimmer breaks - you are SOL! Also, it's far better to have the suction lines separate - it allows more flow to feed the pump. It also has the same problem with keeping the skimmer 'fed' with water if the water level drops. It's also a PITA to winterize!

#3 A reserve line - this is about the only option that makes any sense. When you plumb the pool you run 2 parallel lines from the skimmer to the filter pad, you only plumb one to the pump, but leave the other stubbed up (capped and plugged) to be used if the original line fails for whatever reason. The problem with this is that since the pipes are run together, what breaks 1 will probably break the other, unless it's freeze damage and the reserve line has been kept dry.

As far as I know those are the only reason for the second port in the bottom of a skimmer, if yours is open it's not a reserve line.

For winterizing it needs to have the water blown out of it and be plugged. If it is a balance line or a main drain line, let me know and I'll tell you a way to winterize it :)
Based on this information, I think it is #2.
If I blow air down this second line, if air comes out the main drain, I take it that means it is #2 ?

I am going to try to blow out the line with my Shop Vac, is there any risk ?
 

Catanzaro

Platinum Supporter
TFP Guide
Jul 30, 2014
3,207
Monmouth County, New Jersey
#2
I am closing my pool for the first time. I've figured out a good game plan for blowing out the lines, except I am not sure what to do with the second hole in my skimmer. Based on this information, I think it is #2. If I blow air down this second line, if air comes out the main drain, I take it that means it is #2 ? I am going to try to blow out the line with my Shop Vac, is there any risk ?
There is no risk with the shop vac. Although, you will have to trap air in the line. If this is the main drain, you may want to consider purchasing blow thru plugs with a Schrader valve. I do not know if they ship to Canada. The shop vac may not have enough air volume to accomplish the task. You will have to be very quick in plugging up the port. With the blow thru valves, an air compressor can be used.

Blow-Thru Valve Winter Pool Plugs - Various Sizes
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
10,547
Bedford, TX
#3
kp,

Welcome to TFP.. a great place to find the answers to all of your pool maintenance questions, even if you live in the frozen North... :shark:

If your pool is over 10 years old, the most likely scenario is #2.. One hole goes to the pump and the other hole goes to the main drain.

I can't help with closing questions, because I live in a place where most of us don't close our pools.

Let's see if we can get one of our closing experts to chime in..

That said, I do not understand the theory of blowing out the main drain line when it is connected to the skimmer.. Seems like the water in the main drain line would be the same level as the water in the pool?? Also, unless you have a way to prevent water from flowing back into the main drain, it would just fill up the pipe again??

I'll also be interested in the answers you get..

Thanks,

Jim R.
 

Catanzaro

Platinum Supporter
TFP Guide
Jul 30, 2014
3,207
Monmouth County, New Jersey
#4
That said, I do not understand the theory of blowing out the main drain line when it is connected to the skimmer..
I always tell people to follow the plumbing. If there are 2 connections, one going down to the pool and the skimmer going back to the pump, both in the skimmer housing, then to clear the lines, air will have to be trapped in the main drain and water completely removed in the line from the skimmer going back to the pump. If not threads for a Gizzmo, either antifreeze for expansion or foam rope. The plugs with the valve work real well.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
10,547
Bedford, TX
#5
I always tell people to follow the plumbing. If there are 2 connections, one going down to the pool and the skimmer going back to the pump, both in the skimmer housing, then to clear the lines, air will have to be trapped in the main drain and water completely removed in the line from the skimmer going back to the pump. If not threads for a Gizzmo, either antifreeze for expansion or foam rope. The plugs with the valve work real well.
Cat,

So you add a plug with a valve in the skimmer and then use an air compressor to add air into the skimmer side, until all the water is forced out of the main drain pipe. Is that correct?

If you don't do this I assume the water in the main drain line would freeze?? Does this mean that all the plumbing lines have to be dry when you close?

I am worse than a new-be when it comes to closing questions..

Thanks,

Jim R.
 

Catanzaro

Platinum Supporter
TFP Guide
Jul 30, 2014
3,207
Monmouth County, New Jersey
#6
Cat,

So you add a plug with a valve in the skimmer and then use an air compressor to add air into the skimmer side, until all the water is forced out of the main drain pipe. Is that correct?

If you don't do this I assume the water in the main drain line would freeze?? Does this mean that all the plumbing lines have to be dry when you close?

We have to figure out where the 2 skimmers ports go. The way I explained everything appears to be one run, when I believe they are independent of each other. I believe that if the skimmer level falls, the main drain works as protection. I would wait to hear back from the pool owner.

Best way is to lower the water below the skimmer (with regular pump), then blow air and see which way it travels. If one port goes to the bottom of the pool, the main drain, then you will need to trap air in the line (blow tru plugs). The other line will need to be emptied of water either working backwards to the pump or from the pump to the skimmer. This is the beauty of lowering the water 1" below the skimmer.

I am worse than a new-be when it comes to closing questions..
My knowledge is no different than yours. Today, I just added a schematic in my detailed closing thread that shows travel of air (See below). Then again, a combination skimmer (which I believe is somewhere linked in the thread) is not drawn out on paper. There are many variables with the skimmer/main drain combinations.

Air Travel (Suction & Return).jpg
 

tomfrh

Well-known member
Jan 30, 2018
380
Australia
#7
I have #2 and I agree it’s moronic. Our old pool we built had separate line going to drain and going to skimmer, which made vastly more sense.
 

tomfrh

Well-known member
Jan 30, 2018
380
Australia
#8
Re. The shop vac. I think you’ll struggle to push air down to the main drain!

id just shove some food colour into the hole and plug a garden hose in there.
 
Oct 10, 2018
6
Canada
#10
Is there ever two lines from the main drain ?

I think I have a line not being currently used (I have a picture at home) beside my skimmer line near the pump.

So if my skimmer connects to the main drain, is it possible they would hook up two connections to the main drain ?

Re. The shop vac. I think you’ll struggle to push air down to the main drain!

id just shove some food colour into the hole and plug a garden hose in there.
If food colouring comes out the main drain, I'd have my answer. I'll try it ! Thanks.
 
Oct 10, 2018
6
Canada
#13
Re. The shop vac. I think you’ll struggle to push air down to the main drain!

id just shove some food colour into the hole and plug a garden hose in there.
Only had Soya Sauce. And that worked.

My second hole is connected to the main drain, as that is where the soya sauce ended up.