Durso flushing effect question

[typhoonreef]

I have a 300 gal tank with a dual durso drain line with a single overflow box,1in bulkheads.Just installed a 100 gallon sump through the wall in another room.Had been running with a large sump directly under the tank,was fine.My problem is I am getting a back pressure ,flushing effect, in the durso,not solved by drilling end caps,Durso website says it is caused by a possible dip in the line ,which is my case .Even though it is much lower than the tank water level,going a longer distance and a slight dip has created this issue.Don't think it is possible to change it ,the way I had to put it through the wall.Does anybody know any ways to relieve this back pressure,possible in line relief valve or any other solutions to try.Thanks

 

[typhoonreef]

Anyone?

 

[nauticac4]

have you tried to drill the holes in the caps bigger. Sounds like more air needs to get into the line to prevent the flushing (siphon) from happening.

 

[typhoonreef]

yes, I have drilled holes,

 

[Entropy]

I don't suppose you have any pictures? Are you using flex hose, or hard PVC?

 

[typhoonreef]

Flex hose .Sorry no pictures.About 8ft of hose x2drains

 

[BangkokMatt]

<a href=showthread.php?s=&postid=14464795#post14464795 target=_blank>Originally posted</a> by typhoonreef
yes, I have drilled holes,

You need to make the hole bigger - the flushing will then stop.