Durso Drain Question

Reef_Hobbyist · Mar 3, 2016

I am using 2 durso drains similar to this picture in my overflow box. I also have an third emergency drain pipe that is just an open pipe taller than these to prevent a flood if there was to be a clog.

The water level in my tank and overflow box higher than I want. It is coming up almost to the top of this pipe where the small hole is drilled. If I put my finger over the hole to block the air and increase the siphon it quickly brings the water level down. So I know there is no blockage anywhere. I believe the drains are sucking too much air thus allowing the water level to increase??

My question is, if the durso pipes were shorter would it result in lowering my water level or do I have to consider limiting airflow into the top of the pipe? I don't want to cut anything just yet to experiment with it.....

dbrewsky · Mar 3, 2016

what kind of pump are your trying to use? usually when the box fills like that it indicates that the return is pumping water faster than the durso can handle.

dbrewsky · Mar 3, 2016

also how far under water in the sump is the other end of the drain? if the drain is submerged too far, it can cause issues with the air purging

Reef_Hobbyist · Mar 3, 2016

True. I can close down the valves on the output from the return pumps a little and it fixes the problem. However, I would rather run them full out if I can and I know the drains can easily handle the full volume. In fact, even just one drain out of the 3 can handle the full volume. I just like the durso drains because they are quieter.

Reef_Hobbyist · Mar 3, 2016

dbrewsky said:
also how far under water in the sump is the other end of the drain? if the drain is submerged too far, it can cause issues with the air purging

That was another idea I had. I thought there would be less noise if the return pipes went under water in the sump. I could make them shorter so they are just under the sump water level but not too deep

dbrewsky · Mar 3, 2016

in all reality with the setup you have currently you could do a bean animal and have none of these issues

Whats the gph rating of the pump? dursos are pretty simple technology and they do handle limited flow compared to what to same size pipe would handle under full siphon. MY recommendation is if you want to stick with the durso setup, valve back the return pump. The system is trying to tell you that your pushing too much flow and the only real way to improve the performance of a durso is limiting air in the system and if your air hold gets clogged you will have a full siphon.

Can you post a pic of your plumbing so we can have eyes on as well?

Reef_Hobbyist · Mar 3, 2016

I am going to shorten the length of my drain pipes so that they are not quite so deep under water in the sump. I have been thinking about doing that anyway since it will make changing filter socks easier.

Based on those results, I will also dial back the valve on the return pumps a little if needed. I have been told that reeflo hammerhead pumps are good at moving larger volumes of water but at lower head pressures. Basically they are not all that great at moving water vertically but on the flip side they don't have any head pressure issues if you shut down the output valve a little. Not sure if that is true or not??

Thanks, appreciate your help!!

dbrewsky · Mar 3, 2016

yeah i would keep the drains 2" or less under the water to help purge air from the pipes.

regardless the pump and resistance from head height or valves will reduce the performance of the pump. Throttling back the valve just a bit should not hurt the pump and is the only way to fine tune AC pump outputs. Another option is you could install a valve and redirect some of that unneeded water back into the sump, however this is usually not worth the trouble.