Alamak!!! Cannot Balance Sump Flow To Main Tank!!

[hoppinghippos]

Hi, I've just done the plumbing to my sump after many days of hard work, and connected everything and started the flow, but have a prob tho, just how do you ensure the flow of water from the main tank to the sump is exactly equal to the flow of water from the sump back to the main tank? I"ve connected a T-joint with a valve such that I can control the flow of water back to the main tank with the excess being channelled back into the sump, but its difficult to adjust the valve such that the flow in and out of the main tank is equal. Even after my my best fine adjustment to the valve, I can see the water level in the sump change after say 5-10mins so I"m worried when I wake up tomm, either one of the tank would flood my room!! pls help!! really appreciate all advice!

[Clownfish]

if u hav an overflow, it shldnt pose any problem...

[hoppinghippos]

I do have an overflow, I"m not worried about water draining out of my tank into sump, but worried about water draining out of my sump into my tank and either overflowing my main tank or making my sump pump run with no water spoiling it, so anyone have any idea how to balance the flow? Or is manual adjustment of the return output (using ball valve) the only way?

[killfire]

My plumbing is about the same as yours but I did not fix in a T between the pump and the main tank. The ball valve is connected directly to the piping between sump and tank, and manually adjusted such that the o/p and i/p flowrates are balanced. Suggest that you stay at home at least for a few hours to monitor water levels after adjustments.

Had the same concern as you initially but fortunately the setup is working well and I still haven't flood my house yet ...

[SpiderOne]

water level changing higher or lower? maybe ur pump too powerful/weak?

[Ian]

Sorry but no matter how u tune, the level will still change after some time.

does your pump have a compartment on its own in the sump?

[zephyros]

fren,

so long as your drain out from the overflow to the sump is more than

that been pump back from sump to main tank, you do not need to worry

as this design will balance itself. Only time is that your return flow is over way

too much that can be handle by the overflow, then you had to worry about

the overflow really gonna be overflow.

Your design should also handle the situation whereby your return pump was

shutdown down and all the "excess" water flow back to the sump. Your design

should have additonal "space" for this "extra" water.

Zephyros

[Crab]

I strongly don't encourage this type of setup. What if pump fails or choke, what if piping choke, water level in you main tank & sump will also affect flow rate. You'll be constantly adjusting your valve. Too many what if and high risk of flood.

Suggest you build an overflow, or at least buy an overflow box. If this is really not an option, build a float switch in your sump and put a stronger pump in sump. Sump pump only switch on/off at preset water level.

[SpiderOne]

he IS using an overflow...

[Crab]

he IS using an overflow...

didn't read properly

then I don't understand why they don't balance, they should balance, unless the sump is very small. a float switch should solve the problem.

[MNCL]

Hi Hopping hippos,

I have an overflow too but did not xperiencing(touch wood) such as yours. My overflow uses 2 siphons. With these, water from the main tank is siphoned considerably more than using a single siphon.

Try reducing the amount of water in your sump. Maybe with lesser quantity of H2O, your problem could be overcome.

CHEERS!

[nsyahron]

Make the overflow comb longer, or a bigger overflow box, or double/triple siphon in overflow box. You have to to change one variable at a time to see which one will give the same outflow and inflow. Good luck!

[killfire]

So long as your drain out from the overflow to the sump is more than

that been pump back from sump to main tank, you do not need to worry

as this design will balance itself

Agreed.

your design should also handle the situation whereby your return pump was shutdown down and all the "excess" water flow back to the sump. Your design

should have additonal "space" for this "extra" water. 

You can install a check valve above the ball valve to prevent back flow when pump is cut during maintenance....An easier alternative is to adjust the level of the inflow pipe nearer to the water surface in the main tank. This will prevent large volumes of water from draining to sump during pump shutdown...

water level changing higher or lower? maybe ur pump too powerful/weak?

A weak pump should not be a problem unless it cannot even develop the necessary pressure head to lift water from the sump to the main tank. You only have to be satisfied with a lower rate of inflow …that’s all. If the drain rate is higher than the inflow of water to the main tank, it will eventually balance itself such that drainrate = inflow. And you can never over-drain the main tank since the water level is maintained at the level of the overflow unless inflow > overflow.

water level in you main tank & sump will also affect flow rate.

I don't agree with this. The water level of the main tank will definitely affect the drain rate, but not the inflow since the pump works on a fixed capacity. If your sump is located below your main tank, sump water level has no influence at all on both the drain and the inflow…. Given a fixed pipe diameter, pressure head, etc., you cannot change the rate of inflow unless you are able to control the speed of the motor driving the impeller in the pump or you use a valve to adjust the flowrate….

Sorry but no matter how u tune, the level will still change after some time. does your pump have a compartment on its own in the sump?

Don't quite agree with this either... My setup has been running for about three weeks already without changes in water level in the main tank, but the water level in the sump falls due to evaporation caused by cooling fans. As mentioned, if your pump is running consistently and there is no leakage in your plumbing, it is a breeze to maintain water level in the main tank with just a ball valve..... unless the ball valve is so worn out that it turns by itself due to slight vibrations from the pump

I strongly don't encourage this type of setup. What if pump fails or choke, what if piping choke, water level in you main tank & sump will also affect flow rate.....Suggest you build an overflow, or at least buy an overflow box. If this is really not an option, build a float switch in your sump and put a stronger pump in sump.

I don't think this is a problem unless you have lots of floating garbage in your main tank that gets drained into the pump and clogs up the piping. To be safe, you can always wrap the entry of the drain pipe with a small piece of mosquito net.

Make the overflow comb longer, or a bigger overflow box, or double/triple siphon in overflow box

I am not against the use of overflow boxes or more complicated setups... but then, a cheaper, more cost effective solution is always the best...

[hoppinghippos]

Hi all thanx for your advice! I"ve finally managed to get the flow balanced, but yeah Ian is right, after several hours the water level still changes, so I really don't know how to to up water due to evaporation just by observing drawn water level marks on the tank! sigh.... guess its back to check S.G. and topping up and checking S.G. again.

Sorry to be such a pain in the behind but can you guys help me with another prob? I"ve read in some threads here that using a sump, one can know how much water to top up for evaporation loss cuz the water level changes IN the sump while the main tank's water level is CONSTANT. But after thinking about it, I figured that can't be cuz inflow and outflow from the main tank is constant, so any water loss due to evaporation occuring in the main tank WILL lower the water level in the main tank? So I just need to mark off the present level and top up whenever it drops?

[sunny03]

ya it also best to mark off the present level and top up when ever it drop it always better to top up once a week me also doing a same marking the water level with masking tape

[killfire]

If your water level changes after a few hours, you have not achieved a balance in the flowrates...

I have not adjusted the ball valve on my setup for the past 3 weeks. ... and have successfully maintained constant water levels in my main tank..It is puzzling as to why you can't balance your flowrates since our setups are similar except that I don't have the T joint...

And yes, water top up is always done in the sump... since the water level in the sump drops due to evaporation in both tanks...

But after thinking about it, I figured that can't be cuz inflow and outflow from the main tank is constant, so any water loss due to evaporation occuring in the main tank WILL lower the water level in the main tank? So I just need to mark off the present level and top up whenever it drops?

Think again ... water doesn't evaporate as fast as, or faster than the rate of inflow... otherwise we would have to top up water every hour....

[Ian]

Sorry to be such a pain in the behind but can you guys help me with another prob? I"ve read in some threads here that using a sump, one can know how much water to top up for evaporation loss cuz the water level changes IN the sump while the main tank's water level is CONSTANT. But after thinking about it, I figured that can't be cuz inflow and outflow from the main tank is constant, so any water loss due to evaporation occuring in the main tank WILL lower the water level in the main tank? So I just need to mark off the present level and top up whenever it drops?

For your situation your right, the water level in main tank and sump, both will have different water levels when it evaporates...

As for the common setup:

1) water is pumped into the main tank from the sump,

2) water in main tank rises and overflows into sump.

Therefore main tank water level is constant. So we just check the sump water level for top up.

[hoppinghippos]

YAY!!! My flow is FINALLY balanced!!! Went to sleep last nite, woke up and found the level to be unchanged!!

killfire and Ian: I think the water level in the main tank will only be maintained in the event of evaporation with the water level in the sump dropping only if the overflow in the main tank is such that the water level is exactly at the point where it just spills into the overflow box? but donno if I DIY-ed it wrongly but my overflow box is such that the edge is about 1cm below the water level. So theoretically Inflow = outflow and not inflow= outflow + evaporation? Am I wrong?

[killfire]

YAY!!! My flow is FINALLY balanced!!!  Went to sleep last nite, woke up and found the level to be unchanged!!

Congrats... *clap clap*...you did it!!

killfire and Ian: I think the water level in the main tank will only be maintained in the event of evaporation with the water level in the sump dropping only if the overflow in the main tank is such that the water level is exactly at the point where it just spills into the overflow box?

Wahh.... blurrr... sorry, I am on leave today .. so my mind is a bit switched off... but is that a statement or a question??

but donno if I DIY-ed it wrongly but my overflow box is such that the edge is about 1cm below the water level.

I don't think it matters... as long as your overflow is able to drain water as fast as it is being added into the tank, the water level in your main tank should not rise.....

So theoretically Inflow = outflow and not inflow= outflow + evaporation? Am I wrong?

If we take the sump out of consideration, then inflow to main tank (l/h)= outflow from main tank (l/h)+ evaporation from main tank (l/h)+ change in water volume of main tank (l/h)(principle of conservation of mass). But since main tank water volume (or level) remains unchanged and the rate of evaporation is much smaller than the other flowrates, then inflow = outflow is assumed....

[hoppinghippos]

hahahhaha.... principle of conservation of mass!!!! hahahahha.... are you a teacher or engineer or something?? gosh seldom hear that phrase! I "returned" that to the school a long time ago oredi!

fwah lau, I very confused liao.... hahahha... really blur!!!

[killfire]

hahahhaha.... principle of conservation of mass!!!! hahahahha.... are you a teacher or engineer or something?? gosh seldom hear that phrase!  I "returned" that to the school a long time ago oredi!

It should have been "law of conservation of mass". I am an engineer by qualification and I teach mechanics, CAM, material sciences and processing.

fwah lau, I very confused liao.... hahahha... really blur!!!

Don't worry, at least your flows are balanced.... thats what really matters ...hor??

[hoppinghippos]

killfire: hhmm where do you teach? I just graduated in mech eng myself this yr, could you have once been my prof?