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Tutorial on how to change Red sea Reefer downflow valve to a gate valve


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Hi reefers,

To those who owns a Red Sea Reefer tank will know how painfully annoying the diaphragm downflow valve can be when detritus and mulm clogs the valve. I spent lots of time and effort constantly tuning the valve and at times, the valve can get stuck and become very difficult to make minute changes.

I decided to change the stock valve to a proper gate valve, do note that the sizes are applicable for RSR170, RSR250 & RSR350 only, bigger RSR will likely require different size pipes.

The parts required will be:

- red sea reefer return pump adapter

- 25mm gate valve

- 25mm PVC pipe

- 25mm PVC elbow x2

- 25mm PVC screw adapter

- PVC glue

 - PVC cutter


The RSR return adapter can be bought from red sea dealer and i purchased mine from RMS.


For the other parts, i believe Madpetz carry most of the parts but i bought all of those from taobao.


The first step is to use a spanner to unscrew the return pump fitting from the adapter.


Next, replace the O-ring from the Red Sea return adapter onto the PVC screw adapter, remember to apply a layer of teflon tape to prevent leakage.


Screw the 25mm PVC screw adapter onto the red sea adapter.


Next, measure, cut and dry fit all of the piping to ensure the replacement fits well before glueing.


Next, apply a layer of PVC glue on to the PVC pipes, i usually apply a generous amount and wipe off any exccess. Remeber to always wear glove when dealing with chemicals!


Once all glued and done up, remove the original downflow valve and its time to replace them! 

Oh and i ran out of the blue PVC pipes so i simply connected some left over PVC connectors to make sure the pipe is below water level in the sump.


Replaced and up and running after just 30 mins of drying, usually PVC glue are not real glue but just chemicals that soften the PVC to bond them together, ideally it will be better to leave it to dry overnight but i have not encounter any issue just letting it dry for 30 mins.



The gate valve makes minute changes effortlessly, and my experience from the past few days is that it does not fluctuate at all unlike the original red sea valve. My only regret is not doing this DIY mod when i first bought the tank.

Do note that this 'tutorial' should only serve as a guide if you want to do the same to your RSR, i am not responsible for any wrong part size purchased or any leakage because of this mod.


Thanks for viewing!



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EvolutionZ's Floating Reef:

(Decommed) EvolutionZ's 4ft shallow Mixed Reef Build :

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Hey @Evolutionz I was just reading through this, i have a question, so you used 25mm pipes for all of your fittings. The original pipe on the RSR170 is 32mm, does it matter that the pipe is being downsized? If not, can this be done with 32mm fittings etc, or does the reefer return pump adapter only fit onto 25mm? Any help would be greatly appreciated!

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