A question about riser vents.

[Avast Marine]

On skimmers with a riser tube what is the purpose of the riser vent?
I have two skimmers with gate valve mods. A octopus nw2000 and a css125. By design the octo is very easy to incorperate the riser vent and I have done so. This skimmer performs excelent. The css125 has a tee with a red valve built into the riser so the gate valve is done after the tee and there is no riser vent. This skimmer performs moderately.
Here are some pictures:
octo...
<a href="http://www.flickr.com/photos/58279226@N00/212894378/" title="Photo Sharing"><img src="http://static.flickr.com/83/212894378_3b24056160_o.jpg" width="600" height="449" alt="gate1" /></a>
css...
<a href="http://www.flickr.com/photos/58279226@N00/185084427/" title="Photo Sharing"><img src="http://static.flickr.com/62/185084427_4c49a812d6_o.jpg" width="600" height="449" alt="wc2" /></a>

So I am wondering if it has any benefit to cut off the riser tube on the css and put in a tee so I can vent it?

 

[Avast Marine]

Anyone want to chime in on this one?

 

[Avast Marine]

Someone just guess.................lol

 

[DaveBrader]

The riser prevents back pressure in the skimmer body... makes it flow better with less work for the feed pump to feed the skimmer, and makes it stay in adjustment since back pressure can change...

Dave

 

[toddmcgill]

it looks to me like both skimmers have a method of breaking siphon which is i beleive the main goal of the riser,if i am understanding what you are talking about, one has the large pvc going strait up which will draw air to stop siphons and the other looks like it has the riser capped off for some reason and then has a smaller piece of clear poly tubeing drilled and inserted in the effluent tube to draw air and break siphon, without some sort of siphon break like this you would never be able to maintain a constant level in your skimmer,

im not sure which one of your skimmers is which in your description but my guess would be that if you arent having problems maintaining the level in your skimmer then whatever issues you have arent anything to do with the venting of the effluent line but more likely just diffrences in the effiencency of the two diffrent skimmers.

 

[toddmcgill]

also if you are having maintaining a constant level in the grey and red skimmer i would look at either enlarging the poly tube vent on the elbow , or examine the red cap on the riser to see if it can either be remover to allow venting or has some type of twist to align holes drilled in the side to allow adjustment of airflow into the effluent pipe, sometimes they incorporate adjustments like this to help tweak things to avoid slurping noises.

 

[Avast Marine]

Thanks todd, yes my main problem is maintaining a consistant level in the grey and red skimmer. There is no way to unscrew the cap so I was thinking of cutting the riser tube on this skimmer and installing a tee with a vent, so the output was identical to the other skimmer. Is there a possibility that by doing this I will gain more consistancy?

 

[DaveBrader]

That is exactly what the riser tube is for. It keeps the system open, so there is no back pressure. Back pressure is what causes the level in the skimmer to change, and changing levels effects skimming..

Dave