Noisy Closed Loop

**Reefland** · 12-25-2002, 07:37 AM

Merry Christmas everyone!

Last night I placed my MAG 18 on a closed loop (finally) however it makes a horrible noise. I assume it is from the input side of the pump, and it sounds like the impellar is chopping bubbles. I don't know if it is a bubble though as the output produces no bubbles. Currently I have the pump cut back about half way to reduce the noise which has helped tremendously; if the ball valve is opened more than half, the noise gets a lot worse.

What are your thoughts? If it is bubbles, how do I get it out to get rid of the noise? What steers me away from it being a bubble getting chopped up is I would see bubbles from the output which is not the case.

Details of the loop:
MAG 18
1" in and 1" out
Pump is elevated about 1.5' off the ground

Thanks and again, Merry Christmas!

**kevinpo** · 12-25-2002, 02:58 PM

Scott,
If it were air there would certainly be a ton of bubbles in your tank. I believe you are not getting enough flow on the intake side of your pump and it is cavitating (creating too much of a vacuum). A larger diameter pipe (on the intake side) or a shorter distance to the intake should correct the problem as will reducing the output.

HTH,
Kevin

**Reefland** · 12-25-2002, 06:36 PM

Merry Christmas!

That could very possibly be what's wrong. So your saying do one of 3 things; keep in mind I am currently using 1" in and out and the pump is about 2.5' below the top of the tank:

Use 1.25" on the input or
Use .75" on the output or
Raise the pump closer to the top of the tank

Option 3 would be the easiest for me but will this get rid of the problem or is changing the pipe size the better option?

Thanks,

**organicreefer** · 12-26-2002, 07:12 PM

scott,

1.5 inch pipes are reccomended for the mag 18 and neccesary to acheive the flow rates listed

**reefhead** · 12-28-2002, 11:17 PM

your impeller rod could be snapped--i had this problem

**Reefland** · 01-01-2003, 01:05 PM

Ok, choice #3 did not work. I have the pump currently elevated to 1.5' from the top of the tank and "no dice". I even tried to lay the pump on the top of the tank but when I turned it on, it still made the noise.

Here is what I don't get about the increase in pipe size. If I change the input plumbing to 1.25", will that really make a difference since it has to be reduced to a 3/4" threaded male fitting to hook into the pump?

Regards,

**organicreefer** · 01-01-2003, 01:26 PM

bottom line is -mags are great little submersible pumps, they are not the best pumps when run externally-they make alot of noise and are prone to leaking-ime/o

**Reefland** · 01-01-2003, 01:41 PM

Would you think that submersing the pump in the sump but keeping it on a closed loop would minimize the noise?

**organicreefer** · 01-01-2003, 03:17 PM

thats a good idea

it just might work.

**Reefland** · 01-01-2003, 05:55 PM

Here is a picture of the closed loop as it stands. I have it on the side of the tank while I "tinker" with it.

After sealing, re-sealing and re-re-sealing all of the joints, if I crank it up to full throttle not only do I have the noise, but I have bubbles too. I have to crank it down to about ~500gph (estimate) to not get any noise or bubbles.

**ChrisIsBored** · 01-01-2003, 06:02 PM

You definately want a larger pipe for your input... doing so will create less back-pressure on your pump and should solve your problems.

Here's an easy everyday example, stick your hand behind a fan.... then put your hand in front.

The input side is getting sucked in, but not until it gets to the fan/pump does is get that extra "push". At the point of the pump, your water is expelling through your 1" tube faster than it's actually arriving. Simply creating the larger input gives you a kind of a resevoir of water than can withstand the force of the pump.

;)

**Reefland** · 01-01-2003, 06:31 PM

This will work regardless of the fitting attached to the pump being reducing to 3/4"?

Thanks,

**ChrisIsBored** · 01-01-2003, 06:58 PM

you've got an email Scott.

**Reefland** · 01-01-2003, 07:01 PM

Chris,

I am currently using 1" in and out, however the fittings that attach to the pump are 3/4" threaded. The fitting on the output threads over the pump, the fitting on the input threads into the pump. If I increase the plumbing on he input to 1.25", it will reduce to 3/4" where it connects to the pump since this is what the pump requires. Will this reduction matter if I increase to 1.25"?

**Lunchbucket** · 01-02-2003, 10:01 PM

i am interested in this also. i will be adding a closed loop saturday w/ a mag 950. i was gonna run 3/4" inlet and 3/4" outlets (2 running out of a new wavemaker on the market)

so will this be noisy? or will have to do 1" input and 3/4" outlets or should i reduce them to 1/2"...i have them in 3/4" now and 1/2 are glued together.

also, i only have a 3/4" strainer so would it do anything to ahve a 3/4" stainer..then immediately go to 1" then back down to 3/4" where my ballvalve and union hit my pump?

thanks
Lunchbucket

**jeff967** · 01-02-2003, 10:20 PM

reefland, it took 1 1/4 pipe to stop the sounds you describe, from my closed looped mag 9.5

**Reefland** · 01-02-2003, 11:02 PM

Lunchbucket,

I wouldn't use the same size in and out based on what is being said above. I know from my current experience that using the same size both directions is causing the noise when running the pump past ~1/3 throttle. I don't know if 1 size larger or 2 sizes larger would be better though (larger than the plumbing coming out of the pump that is). See below.

jeff967,

What size is the output on your Mag 9? Michelle mentioned to me last night that maybe I should go with 1.5" in and after reading your post, she is probably right. Heck if I go with 1.5", it should eliminate any possibilities of noise, granted that is what is causing it. I think Saturday I will change to 1.5" and I'll post back and let everyone know.

Regards,

**Lunchbucket** · 01-03-2003, 09:33 AM

jeff967, holy crap 1 1/4" to stop it out of a mag 950!!!! crap man.

ok, so shoud i do 1 or 1 1/4" inlet and 3/4 or 1/2" outlet. i am wondering if i add 3/4 to 1/2" reducers at the ends of my 3 outlets if that would add enough back pressure. this would allow me to not re-BUY all my outlet parts....guess that stuff wouldn't be that much

the unions and valves are what cost the most.

if i have to do 1 1/4" or 1" inlet could i get by w/ using my 3/4" strainer then right into the 1 or 1 1/4"...then reduce it back down when i get to my union and ball valve on the pump?? or would that NOT work?

crap this just throws my hole world for a loop on this.

suggestions/advice please!!
Lunchbucket

**ChrisIsBored** · 01-03-2003, 09:48 AM

Lunchbucket, generally you should use whatever size pvc piping that's on the actual pump itself for your output side. Increasing the size won't really do much for you as you're just pushing the same amount of water through a fatter pipe and you're losing pressure when it finally comes out.

On the inlet side it's a good idea to use a reducer and go larger by 1 size or more depending on the pump.

Hope that helps.

;)

**Lunchbucket** · 01-03-2003, 09:51 AM

ok i will use the 3/4" outlet. but as for the inlet i will prolly try 1.5" and reduce it at teh union and at the strainer. so the majority will be 1.5" except at the ends. sound ok???

Lunchbucket

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