Air Lock Skimmers and Returns -- why not?

[KNIGHTCAP]

I understand the concept of airlocking the main drain. You can't plug it, so blow air until it bubbles, then close the valve at the equipment pad. Its like putting your finger over the top of a straw. On the other hand, we blow out the returns and skimmers, then plug them, so water cannot go back into the line. The conventional wisdom says to leave these valves open all winter.

Would there be any harm in closing the skimmer and retun valves at the equipment pad? That way, if one of the plugs fails for some reason, you have your "finger on the straw", and water cannot back up into that line.

If the valves are best left open during the winter, why is it okay to close the main drain valve? If its okay to close the valves, why not close the skimmers and returns?

Thanks for your thoughts!!

 

[mas985]

Your analogy works well if the straw is kept under water like the main drain. This is a static situation. But with skimmers, the pool is usually drained below the skimmer line so the end of the line is not kept under water. If the pool should then fill with water over the winter above the skimmer lines, the lines would also fill. If then there should be a hard freeze, you risk the lines freezing.

Another problem is that the skimmer lines are closer to the surface where it is colder so even if the pool was not drained below the skimmer line, the lines would not stay evacuated and would fill back up because the lines are more horizontal so it would be tough to trap the air. This is not a problem for the main drain because it is deep and less likely to completely freeze but a potential hazard for the skimmer.

 

[KNIGHTCAP]

I am not suggesting only an airlock for the skimmers and returns. Still blow them out and plug them. But in addition, would it hurt anything to close the valve back at the equipment pad? Is there a good reason to keep the valves open? If there is a good reason (such as, it could freeze if its closed?), why doesn't that reason apply to the main drain valve?

 

[mas985]

Sorry, I missunderstood.

Probably the only reason the skimmer valve isn't closed is because there is no reason to close it. The plug prevents water from entering the pipe so why close the valve. If the plug leaked, the valve wouldn't help anyway.

 

[waste]

Welcome to TFP!!

Here's my understanding of this situation. (biased on experience and some deep reading)

You do the MD that way because there really aren't other options (unless you'd care to dive down and plug the MD while it's blowing and then again in the spring to unplug it ) It's not 100%, but is about the best you can do. Also, as Mark said, that line is probably deeper than your frostline.

Depending on how your pool was plumbed, there is a good chance that the other lines are not deeper than the frostline. Since you can cap them and better freeze protect them, you should!

Some 'old school' pool dudes don't even blow nor cap the lines on the assumption that open ends will allow any ice that forms to expand laterally through the pipe But, according to one article I read, it's possible for the ice to form a plug in the line that causes the liquid water to not be able to expand laterally in the pipe, therefore causing the pipe to break

To set your system up with 'no room for freezing water to move' would be a BAD idea

You would do well to cover the pipe ends at the equipment pad so that no critters or water can enter, but I'd leave the valves open.

 

[X-PertPool]

I would leave them open much like waste said, it's the same reason why you leave the drain cap off the filter and the drain plugs out of the motor. In case water gets in it has a way to get out. Although in some circumstances we do airlock the skimmer line when airlocking the main drain as kinda a backup so if the valve leaked it would have to leak into a pressurized skimmer line. Anyways I still don't like maindrains, I hate having to rely on a valve to be airtight when I've seen them leak. Maybe one day someone will make an electronic valve to shut off the main drain at the bottom of the pool when blowing out the lines. OR! you could just not have a main drain since I question how well they work anyways.