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Overflow sizing


Merrittna
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I am looking at an overflow box on an undrilled tank. The question is for noise purposes is it better to oversize the overflow or max out the flow for you return pump for quieter operation? If your return pump is 800 gph would it be better to go with an 800 gph overflow or go to like 1200 or 1600 gph overflow and run it and 75% or even 50% of the capacity to keep it quiet?

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On my undrilled 55 i have a life reef hob overflow. It has to be sized to the pump. If the flow is too slow then there's not enough velocity in the siphon tube to clear air bubbles. If they collect in the tube you'll eventually lose siphon and your tank will overflow. The one i have is rated at 900 gph or so. Had a 650 pump on it and it collected bubbles. Never enough to stop flow but enougb to get me to go buy a Mag 9.5 to make sure the issue didnt get worse. With the Mag I have had no bubbles collect at all.

To kill the noise.. Add a stand pipe. It won't be silent but it helps a lot. Better yet.. Drill the tank - or take it to your local LFS and pay them a few bucks to do it. It'll be cheaper then a good overflow. It looks nicer (my overflow box is a big ugly pig in my tank) and it will probably be a bit quieter. Definitely worth doing.

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In my experience, a HOB overflow can be noisy at both lower and higher flow rates.  And, as MBS points out, the main key to keeping all the water where it belongs (in your tank and not on your floor) is sizing your pump to your utube siphon capacity.

 

For example, I have an eshopps PF1200 dual drain overflow rated at 1200 GPH.  I was running it for a while with a Jebao DC3000 return (3000 liters / ~800 gph) but I could only run one siphon tube or they would both collect bubbles.  Now I am using a Jecod DCT-8000 (8000 liters / 2100 gph) and I have to use two siphon tubes to handle that volume.  Keep in mind those flow numbers are a 0ft head so I'm not really pushing that much through the overflow.  My overflow could be noisy with either pump size, so I added a silencer (Hofer gurgle buster) in ONE of the two drains in the overflow.  The other is for emergency / relief when the gurgle buster gets restricted.  Right now I clean the gurgle buster every two weeks or so because we are doing a lot of cleaning and pulling hair algae off the rocks which inevitably slows down the flow through the gurgle buster).

 

With HOB overflows you are dealing with the sound of the water flowing into the internal box, water going over the wier in the external box, and the sound of air gurgling in the drain pipes.  It's a delicate balance but there are ways to quiet a HOB overflow.

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Never thought of thought of the air bubble issue. Was considering the CPR devise with a vacuum hose attached so that didn't cross my mind. Tank is full so I don't know how comfortable I am with drilling now. Anybody on here drill with a tank operational from the inside out? How often does drilling fail, in my situation causing a huge mess.

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I run a Hob style rated for 1200 gph with two drains using only one overflow tube. My pump is only rated for 575 gph with the return height. I get some noise from the water going into the overflow box. I made two stockman standpipes for the drains and they run great and are pretty darn quite. I am not as picky about noise as most people either though. Muttley has heard my tank and seen it he is all about drilling so his opinion on the noise level may be useful to you. My previous overflow box was a pf 800 with the same pump I am using now and never had any issues with air in the tube or noise.

Sent from my SM-G920V using Tapatalk

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