Plumbing in UV questions

[hoytoyed]

I have a Pentair 40 on the way and I’m contemplating ways to plumb it in. I have one on a 75 gal tank that I did a closed loop on with a separate pump and then hard plumbed back into the display. These units are too large to be mounted in the cabinet and have to be mounted externally.
This new unit will be for my Cade 1500 and I while I still have to mount the UV outside of the cabinet I’d like to try to avoid a separate return to the display. It would have to go over the side instead of the back etc.
I have 3 manifolds on the return line and was trying to determine if I can do the inlet line to the UV from one of the valves directly above the return pump connection and then do the outlet either back into the other valve above it, or either to a third valve meant for a chiller further from the pump in the return. I’m shooting for a 160 gph flow rate. I should be able to control the flow rate with the valve at the location I would do the UV return. Any advice?

 

[blaxsun]

I'd try to find a way to mount it in the cabinet (maybe along the top?) and modify the manifold so that the return passes through the UV entirely before emptying into the tank (closed loop).

 

[hoytoyed]

I'd try to find a way to mount it in the cabinet (maybe along the top?) and modify the manifold so that the return passes through the UV entirely before emptying into the tank (closed loop).

I may be able to get it in the cabinet but it’s 43 inches long! To achieve a 160gph flow rate for the UV I have to run a bypass system. I’m running an L2 vectra at 75% which gives me about 14x tank turnover per hour or 2250 gph

 

[blaxsun]

I ended up going with a AquaUV 57-watt for the same reason (more compact). If you're going to run a bypass, I would probably run it off the manifold in the second image (you should be able to adjust the flow with that valve).

The tricky part is where to empty the UV. If you end up mounting it behind the tank, you could just empty it into the tank directly. If you mount it in the cabinet you could still empty it in either the tank or in the sump (probably the chamber with the overflow return). You generally don't want it emptying back into the return pump chamber.

I don't think you're getting as much flow as you think. My Sicce SDC 9 delivers just over half of its 2500 Gph rated flow after height, twists and length are factored in. And I run it @45% which nets me around 600-650 Gph.

Realistically, you're probably somewhere in the same range (600-750 Gph) - which is still more than fine (just not maybe as high as you thought).

 

[hoytoyed]

I ended up going with a AquaUV 57-watt for the same reason (more compact). If you're going to run a bypass, I would probably run it off the manifold in the second image (you should be able to adjust the flow with that valve).

The tricky part is where to empty the UV. If you end up mounting it behind the tank, you could just empty it into the tank directly. If you mount it in the cabinet you could still empty it in either the tank or in the sump (probably the chamber with the overflow return). You generally don't want it emptying back into the return pump chamber.

I don't think you're getting as much flow as you think. My Sicce SDC 9 delivers just over half of its 2500 Gph rated flow after height, twists and length are factored in. And I run it @45% which nets me around 600-650 Gph.

Realistically, you're probably somewhere in the same range (600-750 Gph) - which is still more than fine (just not maybe as high as you thought).

So this is the configuration I’d like to see if it works. Either so the UV outlet at valve 2 or 3. Sorry for poor art skills

 

[blaxsun]

I think that could work. The only thing I see you needing is a check valve (or something) at valve #2 or valve #3 to prevent backflow from the return pump.

 

[hoytoyed]

I think that could work. The only thing I see you needing is a check valve (or something) at valve #2 or valve #3 to prevent backflow from the return pump.

That wouldn’t be a problem, I would just have to plan the pvc to have a vertical section for the check valve. It would also be visual proof that there is positive flow from the UV ( in addition to a flow meter) as flow meters will indicate flow either way.

 

[Seachelle]

Hi! I also have a Cade and am struggling with how to set up my UV. Is this what is considered to be a closed loop system? If you plumb this according to the diagram, it looks like not all the water will be going through the UV - some of it would be going up the pipe straight back to the tank. Is that a problem, since not all the water going back will be treated? Also, if you did run all the water through the UV, the UV rates of flow are significantly slower than what is recommended for tank turnover rates. Would it be a problem to slow the rate of return down to match what is needed for UV treatment?

 

[hoytoyed]

Hi! I also have a Cade and am struggling with how to set up my UV. Is this what is considered to be a closed loop system? If you plumb this according to the diagram, it looks like not all the water will be going through the UV - some of it would be going up the pipe straight back to the tank. Is that a problem, since not all the water going back will be treated? Also, if you did run all the water through the UV, the UV rates of flow are significantly slower than what is recommended for tank turnover rates. Would it be a problem to slow the rate of return down to match what is needed for UV treatment?

What flow rate are you targeting with the UV? What size tank? What UV unit? Mine is a Pentair 40 and my target flow rate is 160 gph. I have 180 total gallons tank, minus rocks and sand so I’d like a tank turnover of at least 900 gph or so. That leaves my options as a separate pump for the UV controlled by a valve to reach my target gph, and then emptied back into the display. Or, the picture you see above that keeps my tank turnover high and still pulls water from the sump through the existing L2 pump and runs some of it through the UV using valves to reduce the flow rate, and back into the return line to the display to reach my target gph. Not all water has to go through the UV at the same time; it will eventually all be treated.
I would always recommend that the treated water go back into the display instead of the sump so you’re not continuously treating water that was just treated.

 

[Seachelle]

I didn't want to hijack your thread, but since you have the same set up with the Cade plumbing as I do, I thought I'd ask! I have a Cade 900, which also has the chiller output and the two dosing (?) outputs. I was thinking of running a separate pump in the return section to go to the UV, and then have it join back to the return line going to the display tank. I was thinking I could use one of these outputs to run it back to the return line. My concern is what happens to the water flow because the rate of flow from the UV line is going to be much slower than the water coming straight from the return pump. Will there be a tendency for the water at this juncture to slow or back up into the UV line? I hope this makes sense. I'm pretty confused about how to hook this thing up.

 

[Seachelle]

I realize I didn't answer some of your questions - the tank is a 85 gallon display with a 13 gallon sump. I have a Pentair 18 W with a 219 GPH suggested flow rate for algae/bacteria, which is what I'm wanting to target. I have a Sicce Synchra SDC 6.0 pump 530-1450 GPH rating. If I decide to get a second pump, I'll get something compatible with the UV unit.

 

[hoytoyed]

I realize I didn't answer some of your questions - the tank is a 85 gallon display with a 13 gallon sump. I have a Pentair 18 W with a 219 GPH suggested flow rate for algae/bacteria, which is what I'm wanting to target. I have a Sicce Synchra SDC 6.0 pump 530-1450 GPH rating. If I decide to get a second pump, I'll get something compatible with the UV unit.

I’m a little concerned about water backing up the return line from the UV too. Someone suggested a check valve to stop it from happening. Im hoping that will work.
If you do get a second pump get something larger than you think you’ll need. On my 75 gallon I’m running a Sicce 3.5 and it only will flow about 190-200 gph due to headroom, pipe restriction and length of run etc., even though it’s rated at 3 times that amount.

 

[Reefer Reboot]

Per your diagram in post #5, plumbing the outlet of the UV into Valve #2 won't work because you will have equal pressure at Valve #1 and Valve #2. (Remember, flow is developed by a difference in pressure between two points.) As far as plumbing the UV outlet in to Valve #3, how would you accomplish that? It already has an inlet and an outlet plumbed to it. Is valve #3 a three way valve?
Option #1. What you could do is change the elbow downstream of Valve #3 to a tee and plumb the outlet of the UV into there. Then with Valve #1 open you can throttle Valve #3 to force the water through the UV at the rate you wanted. A flow meter at either the inlet or outlet of the UV will allow you to measure the flow rate. Doing it this way will become a balancing act which will change slightly over time.
Option #2. Just let the outlet flow back to the beginning of the sump. Just like skimmers, nobody runs 100% of the turn over flow rate through it. There will be enough mixing for it to do the job IMHO.
Or Option #3 (the best) Use a separate dedicated pump.
Hope this helps.

 

[hoytoyed]

Per your diagram in post #5, plumbing the outlet of the UV into Valve #2 won't work because you will have equal pressure at Valve #1 and Valve #2. (Remember, flow is developed by a difference in pressure between two points.) As far as plumbing the UV outlet in to Valve #3, how would you accomplish that? It already has an inlet and an outlet plumbed to it. Is valve #3 a three way valve?
Option #1. What you could do is change the elbow downstream of Valve #3 to a tee and plumb the outlet of the UV into there. Then with Valve #1 open you can throttle Valve #3 to force the water through the UV at the rate you wanted. A flow meter at either the inlet or outlet of the UV will allow you to measure the flow rate. Doing it this way will become a balancing act which will change slightly over time.
Option #2. Just let the outlet flow back to the beginning of the sump. Just like skimmers, nobody runs 100% of the turn over flow rate through it. There will be enough mixing for it to do the job IMHO.
Or Option #3 (the best) Use a separate dedicated pump.
Hope this helps.

This is valve # 3 with the barb pointing down. It’s meant to be a chiller connection.
the concern is having positive flow back into the main return line. I don’t know that it’s possible.

 

[Reefer Reboot]

Okay, a little different than the diagram but I see what you've got now. So if you were to plumb the UV outlet to Valve #3 you will still be in the same pressure path as Valve #2, which is to say, it won't work as you want it to. (Disclaimer for the nit picky like me, there will be a very slight pressure differential between V1,V2 and V3 due to plumbing tare but not enough to matter for this situation.)
I still think you would be better off with option 2 or better yet, option 3.
If you are dead set on plumbing it all in to the return line and don't mind cutting into your plumbing to add another valve, I could draw up a diagram for you.

 

[hoytoyed]

Okay, a little different than the diagram but I see what you've got now. So if you were to plumb the UV outlet to Valve #3 you will still be in the same pressure path as Valve #2, which is to say, it won't work as you want it to. (Disclaimer for the nit picky like me, there will be a very slight pressure differential between V1,V2 and V3 due to plumbing tare but not enough to matter for this situation.)
I still think you would be better off with option 2 or better yet, option 3.
If you are dead set on plumbing it all in to the return line and don't mind cutting into your plumbing to add another valve, I could draw up a diagram for you.

This is metric plumbing and I’d prefer not to go the route of cutting up the existing plumbing, and having the hassle of sourcing metric parts, or mating up imperial to metric. I’ll still pull the inlet to the UV from valve 1 or 2 but as the unit will be mounted vertically outside of the cabinet, I’ll either hard plumb the outlet or return of the UV back to the sump, where the current overflow pipes are, or possibly hard plumb it right into the display. I’ll have to add a cutout in the top if I go back to the display, but it’s not a big deal. I’d really like to avoid a separate pump again, though that’s what I did on my current 75, and it works well, but it’s just more noise etc.

 

[Reefer Reboot]

Very good! If you really want to make it easy on yourself add a flowmeter in there to dial in the flow rate you're going for. Best of luck to you.

 

[hoytoyed]

Very good! If you really want to make it easy on yourself add a flowmeter in there to dial in the flow rate you're going for. Best of luck to you.
I’ve got an apex on my smaller tank and am using the flow meter in the UV there. I’ll need to buy another apex, flow meter and another FMM module.
Things add up in a hurry with this hobby.

 

[dlai]

My Lifegard 55w UV just came in today and my head is also spinning from all the different options.

At this point I'm most likely leaning towards just tapping off my return and plumbing the UV output back into the sump. I know not the most ideal but it's the simplist thing for me to do at this point.

Had also considered doing what OP suggest in post #5 of tapping back into the return to display but was worried it would cause pressure issues and then I just wasted all my time redoing my return plumbing.

 

[Seachelle]

My Lifegard 55w UV just came in today and my head is also spinning from all the different options.

At this point I'm most likely leaning towards just tapping off my return and plumbing the UV output back into the sump. I know not the most ideal but it's the simplist thing for me to do at this point.

Had also considered doing what OP suggest in post #5 of tapping back into the return to display but was worried it would cause pressure issues and then I just wasted all my time redoing my return plumbing.

I spoke to someone at my lfs and he recommended just running the UV on a separate pump and running it back to the return section of the sump. He said the uv will be running so much slower than the return pump, so you won't really be recycling the same water through the UV, which was my concern about setting it up this way.