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Tunze Osmolator Universal 3155 Auto Top Off

Tunze Osmolator Universal 3155 Auto Top Off
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  • Tunze Osmolator Universal 3155 Auto Top Off
  • Tunze Osmolator 3155

Tunze Osmolator Universal 3155 Auto Top Off

97% Recommend this to a friend (215 of 221)

SKU: 202307

reg. $209.99

Special Price: $188.99

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Quick Overview

One of the safest ATO’s available. Utilizes an electronic eye sensor to monitor water levels and a backup float switch sensor with audible alarm. A controller protects the quiet metering pump from running dry and reports an empty storage tank. Two magnetic holders for sensors and multiple mounting brackets included.

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Previously Asked Questions

  • by Jeff on November 28, 2013, @2:50 PM

    How much head will the pump push

    Bulk Reef Supply Hey Jeff,
    The pump on the osmolator has a max head height of 7ft.

    Do you find this question helpful?  Yes   No

  • by David on May 10, 2014, @11:50 PM

    Would you happen to know the max head pressure of the Tunze Osmolator's pump?

    Bulk Reef Supply Hi David,
    The max head pressure on the osmolator pump is 7ft.

    Do you find this question helpful?  Yes   No

  • by Spencer on April 29, 2014, @12:54 PM

    I have a litermeter 3 that has failed. It pushes water about 30 feet from the litermeter to a sump tank. Will this pump do the same?

    Bulk Reef Supply Hi Spencer,
    The max head pressure on the included pump is about 7ft. It likely wouldn't be well suited to this application. That said though, you can get the additional switch socket adapter which would allow you to control any pump via the osmolator system. That way you can use a pump that can handle the head pressure.

    Do you find this question helpful?  Yes   No

  • by Ronald on January 13, 2014, @2:32 AM

    Just wondering if I need 2 ATO. I know you can place it either in the sump or in the tank, but my question is if I place it in the sump will it also refill my tank in that process. I don't see that happening but if it does please let me know.

    Bulk Reef Supply Hi Ronald,
    If you have a sump, it MUST go in the sump, in the chamber where your return pump is. This is the only area of your tank that will have a changing water level depending on evaporation (unless its far too late!). Only one ATO would be necessary but it must go in that location if you have a sump.

    Do you find this question helpful?  Yes   No

  • by Christian on July 17, 2014, @9:40 PM

    If i have a wave maker and this ATO in the same tank (I don't have a sump), would the waves cause the pump to turn on and off constantly? Thanks

    Bulk Reef Supply Hi Christian,
    In theory it could present a problem but the circuitry in the Osmolator should help to prevent that. Every time the ATO is triggered it runs for a minimum of 15 seconds. It adds overfill to prevent short cycling. In most cases this should be sufficient unless the height of your waves is constantly changing.

    Do you find this question helpful?  Yes   No

  • by Daire Fontaine on January 17, 2014, @12:23 AM

    My Tunze Osmolator ATO keeps getting stuck in the ON position. I soaked the electronic eye in vinegar and it was fine for a week, but then it stuck on again. Do these electronic eyes fail after many years of use? I've been using it for about 4 years. Is there any way to replace the eye without having to buy a whole new system?

    Daire Fontaine

    Bulk Reef Supply Hi Daire,
    We run into very few issues with these but after that length of time I would imagine its possible for any component to fail. We don't have individual parts like the optical eye, but if you give Roger and company a shout over at Tunze USA, he might. At the very least he could likely help you narrow down exactly what it is. The number I have for them is 512-833-7546 tunze@sbcglobal.net

    Do you find this question helpful?  Yes   No

  • by Mark on June 5, 2014, @8:39 AM

    Does the pump get placed directly in the top off water reservoir? If so what are the dimensions of that pump? I am trying to decide what kind of reservoir I can use before purchasing a ATO.

    Bulk Reef Supply Hey Mark,
    That is correct. Its a submersible pump that gets stuck right into the top off water. If your interested in this ATO system you should give this blog article a quick read. It goes into a lot more detail on the system (which is one of my favorites).


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  • by BILL on November 13, 2013, @7:37 AM

    what pump do you suggest to go with the3155 osmolator?

    Bulk Reef Supply Hey Bill,
    The Osmolator actually comes with the pump right in the package so you don't need to buy one!

    Do you find this question helpful?  Yes   No

Full Details

Bulk Reef Supply tried many different water level switches and auto top off solutions before giving the Tunze 3155 Osmolater Universal Auto Top Off BRS Recommended status. Despite its higher price this is by far our favorite solution. Spending the extra money on a Tunze Osmolater will give you that extra peace of mind and insurance from having a disaster that ruins carpets or hard wood floors.



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  • Super Product By RDM on 2/20/2015

    This was easy to setup and get working. I never realized how much I hated having to manually top off my water until I put this in my system. Now I just check my water levels and the fresh water supply and this takes care of adding water as and when it's needed.
  • EASY and works great By Jeffrey on 2/15/2015

    So far so good ! Have this set up on roughneck bin I'm using to cure my dry rock in. Works perfect and secondary safety offers great piece of mind. In the room one day when pump came on.. manually lifted float and audible alarm sounded and pump shut off. Very comforting to have a piece of equipment like this that is looking out for me ! If you are on the fence, JUST GET IT, you won't be disappointed.
  • fantastic ATO By Hawrasser on 2/11/2015

    this ATO is great. keeps the water level in my sump constant. the only thing i would change is to make the amount of travel on the floating switch a little bit larger. if i turn on my protein skimmer it will sound the alarm but my skimmer is also huge haha
  • Hoping to get it working By Andrew on 1/16/2015

    I have had this on an AIO tank (40 gallon) worked great the first week, now it keeps overfilling my tank( alarm going off) in the process of troubleshooting it with Tunze, hope i can get it to work correctly. I wish it worked right out of the box, but based on reviews the Tunze auto top off is suppose to be the best. I have owned other Tunze products before with no problems. Not bashing the auto top off but its not working out of the box. But Tunze customer service is great at helping.
  • Great ATO! Never missed the target! By Alec on 1/15/2015

    I don't need to add anymore to those 200+ reviews but I put mine on a timer that only turned on once a day for 10 mins. That way it's not pumping all day long and will never over fill.
  • Works Great By John B on 1/10/2015

    Easy set up and I love the optical sensor. My old ATO float valve would often not register the water level depleting and I'd have to refill the sump manually. No issues so far and don't anticipate any. I did have to run the top off line into the tank overflow since my storage container is taller than the sump, but there was plenty of supply hose and I actually like it better.
  • Best ATO ever By Seadog09 on 1/7/2015

    The name alone represent quality so you know from start to finish that's what you'll get. I'm happy with my purchase and I know you will be too..
  • Works flawlessly. By DivingTheWorld on 1/5/2015

    I've had this running for about 4 months now and it works flawlessly. It's really a set it and forget it product. The one quirky thing is that when it first turns on, it will pump water for a few seconds to purge the pump of any air. This is normal and not a but per say, but something to be aware of. I initially had this programmed on my Apex to only turn on a few times a day, but found that it was pumping too much water (due to the starting purge). So now I just leave it on 24 hours a day and it works fine.
  • Works as promised By Jay B. on 1/4/2015

    I bought this to regulate the level in my sump, using RO/DI feed. I also purchased the optional valve. The setup is easy, especially because of the way that the two level sensors are cleverly mounted with the magnetic holder. I turned the water feed on on and everything worked like it was supposed to. Now I don't have to keep fiddling with my protein skimmer to get the right quantity skimmate.

  • Almost perfect By Jim on 12/27/2014

    This is a really great ATO system. There is one downside. If you are pumping the water into your sump, the top level of the top off water container supply cannot be higher than the sump water level. The pump is centrifical, and allows water to flow through the pump when it is off. If the top off water is higher than the sump water, a siphon will occur, and water will continue to flow until the water levels equalize (including over-running the sump, and onto the floor. You simply need to select the right top off container.
  • ATO's Don't Get Better Than This! By Bernie on 12/20/2014

    The Tunze was superior to my first ATO set up which used a float valve and lifter pump. The optical sensor is great and having the second float valve to protect against overfilling is just a smart investment to protect not only your tank but the flooring around it.

    I have a controller in which I could probably have set something up myself but for an all in one package this system is great.
  • Very Cool! By Trent on 12/16/2014

    This is a great product. Easy to setup and trouble free.

    One funny thing is that the way that the LED indicator lights are mounted inside the control box allows for "bleed over" from one light to another. So, in my particular case, the way that I have it mounted inside my cabinet makes the "Too High" appear to be lit when in fact it's the "Level" light. It took me a couple of plug-unplug cycles to figure that out.

    But, it's great product. Recommended!

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