Head pressure on a closed loop?

[NasotheHutt]

How is head pressure figured on a closed loop? Since water floods the entire system when the pump is not running is the head pressure less?

[theatrus]

You will lose some pressure due to fittings, outlets, and pipes. You can use the headloss calculator on this site to figure out how much (use 0 vertical feet of pipe). It will be very minimal though.

[seattlerob]

I believe with a closed loop, there is no "head" pressure loss at all (but loss due to friction thru fittings, 90 degree bends, etc are still valid). I believe normally you would calculate head loss based on the difference in water level height between 2 systems (i.e. sump & tank). With a closed loop, there is zero water level height difference, since it's coming & going into the same system. hth, rob

[rigleautomotive]

if the pump is mounted 5 feet below the tank this would be 5 foot plus any elbo's.

[NasotheHutt]

I trying to figure what pump to get to run a closed loop with an OceansMotions, 2 outlets on each side of the tank, and the inlet off the back. Powered by a pump below, say, 5 feet below the top of the tank. I fugured there would be loss due to the fittings, just unsure about lateral, or vertical runs.

Theatrus's explanation makes sense, thanks!

[theatrus]

Originally posted by rigleautomotive
if the pump is mounted 5 feet below the tank this would be 5 foot plus any elbo's.

Since the pump has the input side at the same level as the output (in the tank), you won't actually. Any loss coming from pushing the water up is made up by the fact that the water is pushing down on the input side.

But then again IANAME (I am not a mechanical engineer )

[NasotheHutt]

But then again IANAME (I am not a mechanical engineer )

Did you stay at a Holiday Inn Express last night?

[rigleautomotive]

i like the blue line 40x.iwalki 30x or 40x will work nicely.i believe you will still have head pressure if you are pushing water up.i have read no info stating the flow down offsets the head pressure.

[RichConley]

Originally posted by rigleautomotive
i like the blue line 40x.iwalki 30x or 40x will work nicely.i believe you will still have head pressure if you are pushing water up.i have read no info stating the flow down offsets the head pressure.

Again, that is incorrect. You are NOT pushing water up. The output and input are the same body of water. You are essentially running a powerhead.

You could mount the pump 300 feet underground, and other than additional friction from the huge length of pipe, it would still work fine.

[smcdonn]

There will be no VERTICAL HEAD LOSS. There will be some losses due to fittings and such though. Very minimal though compared to Vertical Head. Just so everybody knows and I believe it has already been stated, VERTICAL HEAD LOSS is calculated from the height distance between the intake and outlet of a pumping system. As RichConley said, you can mount a pump 300 feet underground and as long as the inlet and outlets don't move, the vertical head loss is the same. Cheers

[MCary]

Ditto...

BTW, Nasothehutt, what size tank and what are you keeping in it. I am slowly deveoping a SPS tank and I hooked my OM on a Sequence Dart. 3600 gph, quiet, reasonable price, and reasonable electrical use.

I also run a Tunze power head. The small one. 1800 gph I think, a small closed loop with a mag 7.5 from the overflow and a 1200 gph return pump, prob 800-1000 gph with head loss.

Mike

[NasotheHutt]

Mcary - My plan is for an Oceanic 58. I was thinking of drilling two holes in each side and one in the back. The two in the sides would be outlets from the OM. Based on what I've seen on the OM website I'll plumb 1&3 on one side and 2&4 on the other, and use the respective drum. That way I can try to replicate a "wave" motion across the length of the tank. I plan on housing SPS. My 1st thoughts were to use 2 Dolphin 2800's, one for the sump return and skimmer, and the other for the OM. Now I am starting to think that will be to much, of both. I was going to go with a down draft skimmer, but have decided to go NW, which looks like NW skimmers require less GPH, so the 2800 would be way to much for the return/skimmer. I also noticed that the OM I was looking at had a 2500 GPH threshold, so I'm back to the drawing board. This tank will signal my re-entry into the hobby after about 4 years off, so I really want to get this right the 1st time. Otherwise my wife will have my head.

N

[navajo]

I don't mean to "muddy the waters" but I have a question I have been turning over in my mind for a bit...

On the surface, it would seem that there is no headloss (due to pushing water up) in a Closed Loop. BUT, on mine at least, the water is being SUCKED into the input of the pipe. So isn't that actually creating a vacuum of sorts, which in turn would actually cause there to be some head pressure on the return line?

In my way of thinking, there would be no headloss if the water was pushing out the return at the same rate that it was being GRAVITY fed into the input of the pump. But since it is being sucked in, does it, in fact, create some head pressure? Just some food for thought.

[NasotheHutt]

Interesting...

I guess having multiple lines running to a T into the pump would allow a greater volume to the pump, and less suction from a single point in the tank.

Mcary - Are those two 1.5" Tee'd together supplying the pump.

N

[MCary]

There is no head loss. I don't know the calculations behind it. But I trust the physics on this one. The is some friction loss.

Yes I tee'd off the intake to reduce the suction in the tank. I didn't want things sticking to it. I could further tee them again on the inside if the suction is still too high.

Which OM are you looking at? I have the OM4 and it works with a 3600 gph dart just fine. It is even used with the barracuda which I believe is over 5000 gph.

Mike

[NasotheHutt]

I was looking at the the super squirt, 2500 GPH. If I max that out I'm turning the tank over 42 time per hour, and that's not including the return from the sump. So I was think that with a reasonable amount of head pressure the Dolphin 2800 would be throttled back to 2000gph or less. Their website claims the pumps can be throttled back via ball valves also, and the power consumption will diminish also.

Another thing...

Do ya'll run your closed loops 24/7, or turn them off during the night cycle?

N

[rigleautomotive]

i run a blue line 40x on 22 hours a day.i had a iwalki 70 for a return pump for a week until i decided it was adding 2 degrees of temp daily.went back to a 40x return and 40x closed loop thru eductors.almost too much flow but i sent it through a squid and i am pleased.nice random flow for amount of power consumption.

[MCary]

I run mine 24/7. I have a Neptune, I could turn it off at night. What have you heard?

[rigleautomotive]

my own observations show the corals put out feeding tenticles when i shut pumps off .i assume it replicates slack tide.but the acros exhibit feeding when closed loop is off for 1 hour or so.i shut it off at 5 am and at 5 pm for an hour eadh.

[NasotheHutt]

I haven't heard anything specific. I was just thinking that the waves crashing on the beach are allot bigger in the daytime, and are reduced to a gentle lap at night. I figure this may be a more natural environment for the inhabitants. I just wonder if the daily start/stop would be to much for an external pump. Heck we time our lighting and add LED's for moon light, why not cycle the current in our tanks accordingly too.

On that note, does anyone change the cycle of their lighting, and LED lighting to mimic the changing seasons, or moon phases?

Sorry to go off in so many directions here, I want to get all this mapped out before I get to far in...

N

[ppurcell]

There may be no vertical head loss, but according to the head loss calculator there is substantial head pressure created if you use less than 2" pipe on the output.

[theatrus]

A daily start/stop shouldn't be a problem for any pump.