Pentair UV Killing Flow

[JPK_Esquire]

For those of you following along at home, I finally got around to bucket testing various scenarios, and think I have arrived at a conclusion for the pressure loss. If you didn't read the original post, I am using a Sicce Syncra Silent 5.0, which allegedly provides 1321 gph. I am running 24" of 3/4" tubing just up and over the side of the sump and then prospectively into the UV laying horizontally on the ground infant of the sump. Results:

• Using the 3/4" barb thread that came with the Sicce pump into 3/4" hose into the bucket = approx. 16 seconds, or approx. 1125 gph
• Using the 3/4" barb thread that came with the Sicce pump into 3/4" hose into 3/4" barb thread on other end of the hose into the bucket = approx. 17-18 seconds, or approx. 1000 - 1058 gph
• Using a threaded 3/4" to 1" slip fitting attached to Neptune FS100 (1" flow sensor) to 3/4" barb thread to 3/4" hose into the bucket = approx. 25-26 seconds, or approx. 692 - 720 gph.

Although I probably wasn't near as scientific as I needed to be, I've concluded that the 3/4" to 1" slip fitting and through the Flow Sensor and then reduced back down to a 3/4" barb thread is where the pressure was getting lost. As I noted above, because the tank is only 200g total volume (probably closer to 15-160g because of aquascape and sand), I only need to run 600+ gph to get into the bacteria algae range I am shooting for. I don't need constant flow monitoring on the UV (only put the flow sensor on there to make sure I was getting the proper flow for the purpose I was intending). I am going to use the fittings that came with the Sicce pump and go into a 3/4" hose directly into the UV and them come out the back using a 3/4" barb.

 

[JPK_Esquire]

Ok, new problem. The UV is heating up the water. I suspect that is because the closed-loop is the small amount of water sitting in the skimmer and refugium chambers of the sump (I.e., the water is being pulled out of the skimmer chamber, passed through the UV, and then returned to the refugium chamber that is same water level as the skimmer chamber). I attempted to rectify this yesterday by moving the return of the UV to the return chamber of the sump (I.e., where the return pumps are located), but that is a real PITA. Because the UV Pump is pushing 900+ gph, I had to turn the return pumps WAY the hell up to account for the extra water that is being pulled from the skimmer chamber and bypassing the rest of the sump. The other concern I have with that setup is that it sets up for potential flooding (I.e., water is being pulled from the much bigger skimmer and refugium sections of the sump and put into the small return section of the sump). If a pump goes down, or the UV Pump doesn't shut off for a feed cycle or if the Return Pumps and UV get out of sync for any reason, I think there is an increased chance of flooding.

So......the options I am considering:

1. Just run the UV something like 12 hours a day at night opposite the eventual light schedule. This is probably the way I will go, as the UV Sterilizer is more a preventative measure than treatment.

2. Re-plumb the UV (again) and run the closed loop out of the display tank. Hard plumb two 90s up and over the side of the tank to soft tubing that will run down the back-side of the display (my glass is painted black, so it will be hidden) into the cabinet below into the Sicce Pump inline (as opposed to submerged in the sump as it is now), through the UV, then soft tube back up two 90s up and over the side of the display on the other side of the overflow from where the UV pulled the water. The concern with this option is head pressure loss. I estimate I am about 900-950 right now, but that is with like 2 feet of head pressure (just over the side of the sump). Up and over the display tank is going to be closer to 6 feet.

3. Attempt to T-the UV return into one of the main returns. This seems to be the most difficult option, and likely isn't going to be done.

 

[Dj City]

Heat can be a problem. I have not had that problem in the past with this same UV on my 110 gallon and I hope not to have it on the 180.

I spoke to someone else at BRS and they said it's perfectly fine to use the 1" meter on a 3/4 inch pipe. He even checked with others in the office and they said yes, you can use the 1" with 3/4 pipe.

 

[Ultra Aquatics]

I have the same UV on my 80g with 40g-Ish sump for about 2 years, have not noticed any appreciable heat from it.

 

[JPK_Esquire]

I have the same UV on my 80g with 40g-Ish sump for about 2 years, have not noticed any appreciable heat from it.

How is yours plumbed/setup?

 

[Ultra Aquatics]

How is yours plumbed/setup?

Currently it’s plumbed with 3/4” barbed fittings and tubing. Going to be re-doing it though with my new tank upgrade, try to make it a little neater

 

[JPK_Esquire]

Currently it’s plumbed with 3/4” barbed fittings and tubing. Going to be re-doing it though with my new tank upgrade, try to make it a little neater

Can you be a little more specific? Are you running a separate pump? Running inline with the return? Flow rate?

 

[Ultra Aquatics]

Can you be a little more specific? Are you running a separate pump? Running inline with the return? Flow rate?

I have it running off a manifold on my return line. Flow rate...never calculated it, I set it to a somewhat slow flow 2 years ago and just let it do it’s thing...

 

[bct15]

Fittings add substantial pressure drop, each fitting or bend you pass through will reduce your flow...and some of them very much so. Setup your plumbing with as few fittings as possible.

it sounds like the sterlizer is dumping wateR in front of its feed pump, essentially recirculating sterilized water through it. Each time it passes through the sterilizer it will heat a little, the slower the flow the more it will heat with each pass (your adding energy to the water via Uv bulbs). You could try to have a longer run of pipe at the outlet to cool the water a little, or dump the sterilized water directly into your display to hopefully cool it down and not send it immediately back through the sterilizer.

you may ultimately need a smaller sterilizer, faster flow through it, or intermittent operation.

Ps, sorry for odd punctuation and capitalization, my phone doesn’t like my fat fingers

also, it could be the extra new pump adding heat as well

 

[JPK_Esquire]

I have it running off a manifold on my return line. Flow rate...never calculated it, I set it to a somewhat slow flow 2 years ago and just let it do it’s thing...

Thanks. I think that is why you're probably not having the same issue. Being plumbed into the manifold (presumable on the way back to the tank) means any increase in the water temp after it leaves the UV is going to likely be cooled or have a dissipated effect by the display tank volume. In my case, the heated water (leaving the UV) is being put back into a small volume of water (approx. 15 gallons) and then at least some of that water is being put back through the UV. The heated water then passes through to the return chamber and back up the display tank.

The result: (1) My display tank temperature is showing about .4 degrees warmer than the water in the sump, and (2) all of the water increases in temperature over time.

 

[JPK_Esquire]

Fittings add substantial pressure drop, each fitting or bend you pass through will reduce your flow...and some of them very much so. Setup your plumbing with as few fittings as possible.

it sounds like the sterlizer is dumping wateR in front of its feed pump, essentially recirculating sterilized water through it. Each time it passes through the sterilizer it will heat a little, the slower the flow the more it will heat with each pass (your adding energy to the water via Uv bulbs). You could try to have a longer run of pipe at the outlet to cool the water a little, or dump the sterilized water directly into your display to hopefully cool it down and not send it immediately back through the sterilizer.

you may ultimately need a smaller sterilizer, faster flow through it, or intermittent operation.

Ps, sorry for odd punctuation and capitalization, my phone doesn’t like my fat fingers

Close. Its not QUITE dumping it in front of the UV feed pump (the feed pump is in the skimmer chamber earlier in sump, and the return is in the refugium chamber on ballast over) but it effectively probably the same volume of water. I agree that I what I think it happening is the water keeps getting heated up each time it passes through the UV. AND....since its only 15 gallons in those two chambers, its easier to heat up.

 

[bct15]

You can increase your return pump size, attempting to have significantly (2x) more flow through your sump than your sterilizer. That should keep mostly new water passing through your sterlizer

 

[DCR]

You must have a relatively low return flow rate if it is heating up your sump. Or is it heating up both the sump and the display? A 40W sterilizer is the same as a 40W heater running continuously in terms of heat input.

 

[JPK_Esquire]

You must have a relatively low return flow rate if it is heating up your sump. Or is it heating up both the sump and the display? A 40W sterilizer is the same as a 40W heater running continuously in terms of heat input.

It’s heating up both. But your question does raise the thought of potentially increasing flow through the sump. Currently, I’m running about 980 gph. The UV pump is about 900-950. So if I increase flow through, then maybe that will move more of the water up to the display. Will try and see if that addresses the issue.

 

[JPK_Esquire]

So I increased the flow through the sump. I’m currently running about 1050 gph through the sump, which is about the max with 1” drains. Temperature still ticked up with the UV on. I am somewhat convinced it’s because the water is being heated and put back I to the same approximate 15 gallons. If I put a 40w heater in a 15 gallon tank it would certainly heat it up.
Next thought is to give returning the UV to the return section of the sump another try.

 

[ca1ore]

Hard to see how the way you plumb the UV could have any bearing on the heating. If you were seeing the sump warmer than the display then you don’t have enough flow to the display. Otherwise it’s simply a matter of the UV adding 40 watts of heat to the tank continuously.

 

[JPK_Esquire]

Hard to see how the way you plumb the UV could have any bearing on the heating. If you were seeing the sump warmer than the display then you don’t have enough flow to the display. Otherwise it’s simply a matter of the UV adding 40 watts of heat to the tank continuously.

The UV is heating water in the sump (like the heaters do) and then that heated water is sent to the display tank. The problem is that instead of the UV return water (which is heated from flowing through the UV) being sent to a large volume of water where the heated water is dissipated, it’s put into a small amount of water, a portion of which is then resent through the UV.

 

[ca1ore]

Your explanation before was clear, but I think you misunderstand how thermodynamics work in a closed system. If you have such poor flow between the sump and display such that the former is warmer than the latter then that’s a problem. One of the principal reasons to run at least 2-3 times display volume through the sump is to avoid precisely this temperature differential problem. Assuming your flow is adequate and temperatures of sump and display are the same, the fact that your UV closed loop may be recycling a small percentage of sump water is immaterial. Its really just heat input and heat output. Your system loses a certain amount based on ambient temp, humidity, volume and surfaced area and it adds heat from all generating sources. Your tank is running hotter because you have additional sources of heat generation, not because a small amount of water is being recirculated.

I remember years ago when the lifeguard modular system first came out. LFS explained to me that I could run a much smaller heater because it only had to heat the half gallon of water contained within the heater module. Nonesense of course because whether one uses a heater module or not, the system still loses the same amount of heat from all radiating surfaces as it did before.

 

[JPK_Esquire]

Your explanation before was clear, but I think you misunderstand how thermodynamics work in a closed system. If you have such poor flow between the sump and display such that the former is warmer than the latter then that’s a problem. One of the principal reasons to run at least 2-3 times display volume through the sump is to avoid precisely this temperature differential problem. Assuming your flow is adequate and temperatures of sump and display are the same, the fact that your UV closed loop may be recycling a small percentage of sump water is immaterial. Its really just heat input and heat output. Your system loses a certain amount based on ambient temp, humidity, volume and surfaced area and it adds heat from all generating sources. Your tank is running hotter because you have additional sources of heat generation, not because a small amount of water is being recirculated.

I remember years ago when the lifeguard modular system first came out. LFS explained to me that I could run a much smaller heater because it only had to heat the half gallon of water contained within the heater module. Nonesense of course because whether one uses a heater module or not, the system still loses the same amount of heat from all radiating surfaces as it did before.

I appreciate the comments, but how do I explain that when the UV Pump and Sterilizer are off, temperature is stable. As soon as i turn it on, it begins to rise?

 

[JPK_Esquire]

Update: Return from the UV Pump/Sterilizer now goes into the Return chamber of the sump. The issue I was running into was water level getting too high in the return chamber (I.e., because 950 gph is bypassing the sump and running straight into the return section). The solution? Raise the baffle (a little annoyed at myself that i didn’t think about it sooner). Now, however I only have technically 1x turnover through the sump that isn’t the UV Sterilizer.

If it’s not one thing, it’s another!