Beginner Plumbing Question

[Lark]

So, I got a great tank for very little, even though the set up is not ideal. One of the loops (closed loop to cannister filter -- no sump) runs from a drain inside the built in overflow box to a return. The drain is a 1 1/4 bulkhead and the return is a 3/4.

Anyway, the problem is that the pump is draining my overflow faster than it will fill. The slots at the top of the overflow can't keep up, basically. So I get a waterfall noise and the overflow comes close to running dry.

I would like to figure this out with the least amount of retrofitting. Perhaps it wasn't the wisest choice, but from the bottom of my drain, I used 1 1/4" spa flex, which I reduce right at the inlet to the pump. I also have in line there, though, a ball valve. If I close the ball valve a bit (on the intake side of the pump), I fix the problem. It reduces the flow enough that the overflow box can keep up with drain. I have heard, however, that ball valves are not great for reducing flow -- that you want a gate valve for that. This would be a very difficult plumbing change for me to make. Anyone see any long term problems if I just close the ball valve a bit to reduce flow to my pump?

The other two options I though about are (1) reducing the size of the intake strainer inside my overflow box. I could use a reducer to go from, say, 1.25" to .75". Not sure if this would work. (2) Opening up or enlarging the spaces on my overflow box -- I'd probably use a dremel or something and this would obviously be difficult since there is water in the tank and there would presumably be little acrylic shards flying all over the place.

Any other thoughts?

 

[Anonymous]

First, do not block the intake side of you pump. You will damage the pump. Only restrict the flow on the out put side.

For our application a ball or gate valve is just fine for regulating flow.

I think you do not have enough water in your tank. Since it is just a closed loop it should not be doing what you are describing. You need to fill up the tank and canister filter completly before you turn it on. You piping is more than large enough. Make sure you keep your top up water up or thie will happen again and you will burn up the pump.

 

[PJsea]

I agree. Don't restrict drain flow with either a valve or by making the lines smaller. Place the ball vallve on the return line. You could also get a smaller pump. You didn't say what you were using.

 

[Lark]

I agree. Don't restrict drain flow with either a valve or by making the lines smaller. Place the ball vallve on the return line. You could also get a smaller pump. You didn't say what you were using.

It's an iwaki 30 rlt. So, just to be clear, if I slightly close the ball valve that comes after my cannister filter, you think this would be ok? This raises the psi in my cannister filter, which is probably a good thing anyway.

 

[PJsea]

You should be fine.

 

[Lark]

That doesn't seem to be working. Reducing the flow on the output side of my pump doesn't seem to make the water drain out of the overflow any less quickly.

I'm actually not quite sure what people mean when they say not to restrict flow on the input side of my pump. The pump has a 3/4" inlet, but my bulhead is a 1 1/4". Why is using a reducer on the overflow side of my bulkhead (or close the ball valve a bit) any different than if I'd just used a 1" drain? Why would the pump care? I also have a strainer in the bulkhead inside the overflow box. Isn't this also "reducing the flow." How is this different from closing off the ball valve just a bit?

Put another way, if I used bushings to just make my drain a 1" drain, and then used 1" spa flex instead of the 1 1/4", would this make a difference?

I guess maybe the answer that I need a smaller pump is the right one, but I've never really heard of an overflow box not keeping up with an iwaki 30. Maybe I have something else going on here, but I can't figure it out.

 

[PJsea]

Agreed, there are many restrictions on the suction side of the pump and likely won't affect the pump performance. It is a general rule/practice not to restrict the pump suction. Centrifugal pumps can cavitate if the suction is throttled. Not a real problem with these pumps. In any case, throttling the outlet should work.
Your pipe size is fine. Either you need to throttle more or look at your overflow to make sure nothing is wrong. Start with it closed and open it until you start having problems.
Check for blockage.
How many linear inchers of overflow do you have?
Also, not having enough water volume in the tank could be contributing.

 

[Anonymous]

That doesn't seem to be working. Reducing the flow on the output side of my pump doesn't seem to make the water drain out of the overflow any less quickly.

I'm actually not quite sure what people mean when they say not to restrict flow on the input side of my pump. The pump has a 3/4" inlet, but my bulhead is a 1 1/4". Why is using a reducer on the overflow side of my bulkhead (or close the ball valve a bit) any different than if I'd just used a 1" drain? Why would the pump care? I also have a strainer in the bulkhead inside the overflow box. Isn't this also "reducing the flow." How is this different from closing off the ball valve just a bit?

Put another way, if I used bushings to just make my drain a 1" drain, and then used 1" spa flex instead of the 1 1/4", would this make a difference?

I guess maybe the answer that I need a smaller pump is the right one, but I've never really heard of an overflow box not keeping up with an iwaki 30. Maybe I have something else going on here, but I can't figure it out.

The water will drain out the overflow as fast as gravity will allow it. You do not restrict the flow on the input side of the pump because it will lower the input pressure and cause the pump to cavitate, which damages the impeller over time.

You piping is sized find. It is what I would do with that set up.

From what you are describing you do not have enough water in your tank.

When you turn the pump on the water level in the tank will rise due to the losses of going throught the overflow teeth. Since you are running this as a closed loop the only place the water can be made up from is your overflow. Add water and you should be fine.

 

[Lark]

Ok, will do. Obviously, my concern if I add much more water and the overflow doesn't keep up is the water coming up to the top or over the tank. I'm pretty close to that point right now, but maybe I'm just not understanding.

I don't really want to be in a position that every time there's a little evaporation, my overflow stops being able to keep up. Also, what if I want to be gone for a weekend and can't add water every day? Auto top off is not really an option for my set up.

I'll try more water and see what happens, though. Thanks everyone.

 

[Anonymous]

If it really is a closed loop you will not be able to overflow. With the way you are set up evaporation will be an issue. Your overflow area is acting like a sump. The water in the tank goes up when you turn on the pump so the same volume of water goes down in the overflow (sump).

If you are concerned about overflowing add the water while the pump is running and see what happens.

 

[Lark]

This make sense. Thanks Mark.

I wonder whether I could just drill a hole in the side of the overflow box and put some kind of screen on it to make sure that the overflow stays flooded even with evaporation.

 

[Anonymous]

You could but then you SG woulf swing. It would be better to come up with some way to top off automatically. With your small system you would probably do well with a float switch that would turn on a small pump that is in a tub of fresh water. When you get that far post to get some ideas.

 

[Lark]

What does it mean that my SG would swing?

 

[Anonymous]

The specific gravity (how much salt is in the water) when you get eveaporation only the water goes, the salt stays behind. If enough water evaporates the water will get more salty (SG goes up) if it goes high enough it can cause problem. When you add fresh water back the water becomes less salty (SG goes down) The the swing is wide enough or often enough it will stress out your tank critters and kill them. To have a healthy tank you need to keep the SG, Temperatuure, Ph etc stable. The reef environment is the most stable environment on earth. Reef critters are not use to large flucuations in any thing.

 

[Lark]

I gotcha. I plan to top off frequently, but just wouldn't mind a little safety zone if I need to be gone for a weekend or something.