Plumbing for UV Sterilizer

Reef4home · Dec 14, 2020

I'm new to the forum and have posted only once before to introduce myself. I'm still setting up my Red Sea xl300 and have some questions about PVC plumbing for additions to the basic set up that comes with the tank. Let me begin for apologizing about the detail here. I'm just trying to get this right and have absolutely no experience at any of this. First, I've purchased a Pentair 25W UV Sterilizer, a Neptune flow monitor kit, and a Varios 6 pump exclusively to service the UV Sterilizer (I have a Sicce 4.0 for the main circulation pump). My plan is to put the Varios in the sump compartment with the skimmer. My understanding is that it would be best to put it in a separate compartment after the skimmer. Is that right? If so, I don't think I can do it anyway because don't think the xl 300 skimmer's footprint allows me to put it in the compartment after the filter socks but before a third separate compartment in which I could put the Varios). In any event, my plumbing question is about the order of plumbing, pipe sizes, and fittings. The Varios has a 1.25" union fitting, the flow meter has a 1" union fitting, and the Pentair Sterilizer has a 1.5" union and a 1" barb. I believe I'm supposed to install a ball valve between the Varios and the flow meter as well, so I need to have the right size ball valve. My question is what diameter pipe I should use between all of these connections. Is it as simple as getting a union fitting that reduces out of the Varios from 1.25" to 1" and then using 1" pipe from there on out? Any advantage to using 1.25" pipe from the Varios through the ball value and then using a 1.25" to 1" going into the flow meter, and then using 1" pipe back into the sump in the compartment containing the return pump? Finally, I'm mounting the UV Sterilizer vertically in the cabinet. Should I have its bottom rest on the bottom of the cabinet (perhaps on a silicone mat), or should I plumb it so it is suspended in air, or perhaps clipped to the side of the cabinet? Also, if there's anything off about any of this reasoning or set of questions, please don't hesitate to let me know! Many thanks in advance for any assistance.

DC Reefer · Dec 14, 2020

First Welcome to R2R!!! Here are my thoughts:
1 - I would keep everything consistent at either 1.25" or 1" just to keep it simple. I think either would be sufficient. If you go 1.25 then you can still do 1" in and out of the UV.
2 - Have you considered plumbing the UV into your return? That is generally best practice. Then you would only need one of the two pumps
3 - I would not have the UV suspended without attaching it to something solid. For mine I zip-tied it to part of the sump stand. I hard plumbed my UV, just used Male adapters rather than the barb and you can easily go either 1" or 1.25"
4 - make sure you can either easily remove the UV for maintenance and or you have room to change the bulb out (do every 12 months)
5 - for the flow meter I would run on either before or after the UV so you can monitor the flow through the UV. Not sure that you need a ball valve for the flow meter unless you want to modify the flow. If you have the ball valves like mine for the UV you can control the flow with those ( would use the one before the UV to control the flow).

Below is my UV. With the three ball valves I can totally bypass the UV for maintenance and still keep my return going or remove it for maintenance. I also have room above the UV to change out the bulb. (I know need some wire management

). My flow meter is above my manifold that feeds my frag tank, so I only get the volume going to my DT. I may add a flow meter to the frag so then I will get total flow through the UV.

Reef4home · Dec 14, 2020

Hi DC Reefer! Thanks for your very thoughtful and helpful reply. My thoughts are below:

1 - I would keep everything consistent at either 1.25" or 1" just to keep it simple. I think either would be sufficient. If you go 1.25 then you can still do 1" in and out of the UV.
Thanks. I'll follow your advice and use 1.25" throughout.
2 - Have you considered plumbing the UV into your return? That is generally best practice. Then you would only need one of the two pumps.
I decided to use a second pump (the Varios 6) just for the UV sterilizer so I can set and change the flow rate on my UV sterilizer either to kill bacteria and algae (fast) or parasites (slow). The Varios 6 is also great for controlling speed. That way I can keep the tank circulating at the ideal constant rate without compromising the optimal flow rate for my UV sterilizer objective. Does that make sense?
3 - I would not have the UV suspended without attaching it to something solid. For mine I zip-tied it to part of the sump stand. I hard plumbed my UV, just used Male adapters rather than the barb and you can easily go either 1" or 1.25"
OK. I'll see what works in my cabinet.
4 - make sure you can either easily remove the UV for maintenance and or you have room to change the bulb out (do every 12 months).
I'll have to remove the UV sterilizer for maintenance, but given that I have it on a separate pump, all I'll have to do is use union fittings before and after the UV sterilizer so I can just shut off the pump and unscrew it from the pipes. Again, if I'm missing something, please let me know.
5 - for the flow meter I would run on either before or after the UV so you can monitor the flow through the UV. Not sure that you need a ball valve for the flow meter unless you want to modify the flow. If you have the ball valves like mine for the UV you can control the flow with those ( would use the one before the UV to control the flow).
I guess the ball valve is just an additional option for controlling the flow in addition to the controllable pump. I also wondered whether the flow meter should be right before or right after the sterilizer, but I've seen a few set-ups where it was installed before the sterilizer, so I was following that thought. I'm not sure whether it matters, though. Thanks for your picture. That's helpful. As to wire management, that's just the icing on the cake. I'm sure you'll eventually do it. I won't be able to think about that until I see everything piped in under the cabinet. As to your frag tank, I'm not sure I'll have one. I really don't know much about them and whether I should make sure to plumb everything so that !I can easily add one down the road. The xl 300 comes with a refugium, but will I need to add a frag tank? Suggestions welcome. Many thanks again for your reply!