Decreasing diameter of drains?

[meermann]

Guys, I have Aquatlantis Aquaview 65, around 45G (slightly bigger than Reefer 170) and undecided yet should I change the drains or not
Originally it came with ~ 1 1/2" (actually 40mm, but it's pretty close) both main drain pipe and emergency. But bulkheads itself are 1 1/2"only (32mm actually but it's almost the same) and the hoses also have 1 1/2 inches diameter.

For return line I use Jebao DCP 2500 at the moment (around 50% +/-), it's more than enough. Also I keep the main drain at least on 50% closed using ball valve, otherwise it's gurgling and making a lot of bubbles and becoming much more noisy.

The main goal is: to reduce amount of noise that's produced by current setup.
So the idea is: to replace main drain pipe with 1", before and after bulkheads, as well as replacing gate valve to 1".

Will it help guys or better to move forward with original setup?

 

[Beau_B]

I used to have a similar size set up and used a dcp3500, drains were 1” and I didn’t have any issues.

However, with your drain on full siphon I'm unsure how sizing down would reduce the noise. For the same volume of water it would need to increase velocity, which may increase noise (theoretically, probably not noticeably).

My guess is your noise is related to water height around the pipe/overflow.

 

[meermann]

I used to have a similar size set up and used a dcp3500, drains were 1” and I didn’t have any issues.

However, with your drain on full siphon I'm unsure how sizing down would reduce the noise. For the same volume of water it would need to increase velocity, which may increase noise (theoretically, probably not noticeably).

My guess is your noise is related to water height around the pipe/overflow.

Well, I was trying to make it a bit more quiet in different combinations.

The problem is: when it's in full siphon mode, it's really silent but (at least my) DCP-2500 has a kind of fluctuations in performance, so if the level fallen down, I hear slurping sounds. And if it works a bit more hard than expected, emergency drain will be used. Between these 2 modes everything is quiet and fine. I investigated a bit and found that the problem with fluctuations is pretty common for Jebao pumps.
My overflow is not completely sealed by design, it has "ventilation" holes near the bottom of the box, so the level in the overflow box = the level in the tank.

So the idea was: convert full siphon to Durso, in that case there are bubbles in the drain pipe, but water level is more predictable (at least it's not expected to be raising up).

With Durso, I've noticed if I reduce the pipe diameter after the gate valve (32 => 25), amount of bubbles will be slightly decreased. Have no idea why it happens.

Because of this I thought that decreasing the inner diameter will help, maybe I was wrong.