Durso standpipe issues with addition of new pump

[rudy]

I have ran a mag 1200 on my system with a 1.5 inch fitted bulhead as a drain. I have a durso standpipe on the drain to minimize the noise. I have just added a mag 500 for extra flow and to run a u.v. sterilizer and upon doing this my durso is not working any more. The water will fill up in the overflow and then drain rapidly into the sump. Any ideas on what is going on and what I can do to correct it?

[Chin_Lee]

i suspect you may not have enough air getting into the drain to allow the water to exit smoothly therefore causing a siphon at a certain level when filling up. Also check the air hole for salt creep which in turn decreases the air into the durso. If the hole is unobstructed, drill a hole the next size up on your drill bit set and test it out.

[rudy]

Thanks Chin Lee. That worked.