HELP! My pump empties out the bio filter!

[TooManyPets]

Hi, I am really looking for help! This is a brand new construction pond. Gravity flow.

I have a 4" Koi Toilet 1 bottom drain connected to a drum filter with a 4" pipe. The drum filter is connected to a 40"x48"x3' deep biofilter by a 4" pipe. The biofilter doesn't have any media in it yet, just water. From the biofilter, 4" pipe transitions to a 2" pipe and connects to a variable speed ES 8500 pump. From the pump the water goes through a transition of 2" pipe, to 3" pipe, and to 2" TPR. Diagram attached.

When I turn the pump on, it rapidly empties the biofilter. Even when set to a somewhat slower speed, it pumps the water out of the biofilter pit faster than the gravity flow can fill it.

My only idea is that I have the gap between the liner and the dome cover set too small. I think it is about 1/2". Any other ideas before I go diving into the ice-cold water?

Any help will be greatly appreciated!!!

[Leecm3]

Couple of questions.

1. What is the height of pond water level (pond surface water) in relation to your drum filter?

2. What is the height relation of 4” output from drum to 4” input to bio filter?

3. Would it be possible to place a 2” T or Y fitting on the 4” line between the drum filter and bio filter and run 2” line to another T of Y fitting on output line of bio filter before input to pump with a ball valve that would allow you to adjust flow on 2” line. This may help to reduce the drawdown (not sure if this is correct term) on the bio filter.

Edited: wanted to add that I think it might be better if your pump was between drum filter and bio filter. Just not sure what the effect would be with gravity output from 4” line with the 2” reducer coupling to.

[lomaponder]

Hi, I am really looking for help! This is a brand new construction pond. Gravity flow.

I have a 4" Koi Toilet 1 bottom drain connected to a drum filter with a 4" pipe. The drum filter is connected to a 40"x48"x3' deep biofilter by a 4" pipe. The biofilter doesn't have any media in it yet, just water. From the biofilter, 4" pipe transitions to a 2" pipe and connects to a variable speed ES 8500 pump. From the pump the water goes through a transition of 2" pipe, to 3" pipe, and to 2" TPR. Diagram attached.

When I turn the pump on, it rapidly empties the biofilter. Even when set to a somewhat slower speed, it pumps the water out of the biofilter pit faster than the gravity flow can fill it.

My only idea is that I have the gap between the liner and the dome cover set too small. I think it is about 1/2". Any other ideas before I go diving into the ice-cold water?

Any help will be greatly appreciated!!!

Contact the koi Club of San Diego. They’ll have a solution ( and they’re a fun bunch(.

[rayjay]

Your drawing shows the RDF physically higher than the bio chamber, but lets' assume your RDF and the bio are at the same physical level as indicated buy the water level being the same in the two (and the pond) when the pump is off. If so, I believe your RDF is under sized. I have basically the same setup and I have to throttle the pump output to multiple returns (4) because the throughput of my RDF is not large enough. Try throttling the pump more than “somewhat slower” to find the sweet spot. BTW what size is the RDF?

[batman]

Look at drawdowns at each point.

When running if the water level in the RDF is low outside of the drum and low inside of the drum then supply to the RDF is the problem.

When running if the water level in the RDF is low outside of the drum and high inside of the drum then the problem is the RDF can't work at this high of a flow rate.

When everything is off how full is the RDF?

[coolwon]

After draining,does the water from the bottom drain rush in to replace whats been delivered to the pond

Oversized pump?

Throttle the discharge pipe after the pump to the pond return or tpr and see what amount of water controls the draining of the filter.

[TooManyPets]

Thank you for taking the time to try and help!

1. I have clarified the drawing and marked the water level. At rest, there are 9" from the bottom of the 4" intake on the drum to water level;
2. Drum output is level with the bio input;
3. Since I need the maximum amount of water to flow into the Biofilter, I don't think splitting the 4" line into 2 2" lines will help there. I have a ball valve in front of the pump. Restricting flow through it is definitely helping! I am not sure if that is good for the pump longevity though...
Unfortunately moving the pump is not possible.

[TooManyPets]

I will try that, thank you!

[TooManyPets]

Thank you for your help! My RDF is rated at 5,500 GPH. I am waiting for documentation on the pump. It gives only RPMs and not gallons per hour. When I throttled the pump to the minimum RPMs, it blew the circuit breaker I will try to throttle the TPRs next!

[TooManyPets]

I really appreciate your effort to help!
When everything is off, there are 9" of water in the RDF with 5" above the top of the 4" input and output.
When I turn the pump on, the level of water outside of the drum is at a normal level, but inside of the drum, it is much lower. The water only comes 1/2 way the output pipe.

[TooManyPets]

After draining,does the water from the bottom drain rush in to replace whats been delivered to the pond

Oversized pump?

Throttle the discharge pipe after the pump to the pond return or tpr and see what amount of water controls the draining of the filter.

Throttling of the discharge pipe or significantly reducing the RPMs causes the pump to trip the breaker. When the pump is on, the water level within the drum becomes quite low, so not enough water is rushing into the bio filter.

[One Poet's Garden]

Thank you for your help! My RDF is rated at 5,500 GPH. I am waiting for documentation on the pump. It gives only RPMs and not gallons per hour.

Seys here that pump can do 8500 gallons per hour: https://www.advantageman.com/product_p/es8500.htm

If it's running full bore, and the RDF can't support more than 5700 GPH ... ?

This site says the pump has variable speed options, all the way down to 2000 GPH: https://www.naturalcurrent.com/es850...-feature-pump/

Good Luck!

[Kathy]

If your water level within the drum, which is the incoming "dirty" pond water, is low, then you're not getting sufficient flow from your bottom drain into your drum. Being that it's a gravity fed system, you may need 2 or more incoming lines to supply enough water for your rdf to keep up with your pump flow. We're pumping 5-6000 gph after frictional and head loss and have 2-4" bottom drains and 4" skimmer line gravity feeding to the rdf. We get a drop in our bio (anoxic) filter as the rdf screen becomes dirty, then after the cleaning cycle, the water level rises in the bio filter. Our rdf is a Draco from Zac Penn so it could be the same as yours. What's your pond volume?

[batman]

When RPM is adjusted lower is the pump tripping an overload breaker or a ground fault breaker GFCI? Some variable speed drives create noise on the line. Breaker might need replaced if the pump is running within specs.

Do not restrict the suction side of the pump. Always restrict the output to reduce flow. With a variable speed pump restriction shouldn't be necessary.

[L5Vegan]

My only idea is that I have the gap between the liner and the dome cover set too small. I think it is about 1/2".

This shouldn't be an issue. I couldn't find the exact specs of the bottom drain, but with a guess of a 12" diameter dome a 1/2" gap would give an area of 19 square inches. The area of a 4 " diameter pipe is just over 12.5 inches so the dome gap wouldn't be the limiting factor.

[TooManyPets]

Thank you to everyone who has offered help! I am up and running!

There were three problems:

1. My drum filter screen needed to be cleaned a few times. Clay silt had it clogged and I was waiting to establish running water level before turning the drum on;
2. Variable speed pumps trip GFCI circuit breakers unless you have a particular Seimens breaker;
3. I still don't have enough water rushing into the drum unless I run the pipes on low. I wonder if my pond liner is getting sucked into or is bulging into the bottom drain gap. I have a pretty steep slope towards the BD. The only way for me to find out is to dive in and check the gap

[Paul Sabucchi]

Thank you to everyone who has offered help! I am up and running!

There were three problems:

1. My drum filter screen needed to be cleaned a few times. Clay silt had it clogged and I was waiting to establish running water level before turning the drum on;
2. Variable speed pumps trip GFCI circuit breakers unless you have a particular Seimens breaker;
3. I still don't have enough water rushing into the drum unless I run the pipes on low. I wonder if my pond liner is getting sucked into or is bulging into the bottom drain gap. I have a pretty steep slope towards the BD. The only way for me to find out is to dive in and check the gap

I hope the climate in California is mild, would not like to dive in mine at the moment the water in my pond is at 43f...

[batman]

Many swimming pool shops stock GFCI breakers that will work with variable speed pumps. Pentair brand (might be made by Seimens) are common. Some have reported placing ferrite core RF chokes on the power cord help. Measure cord diameter and match on Amazon for chokes.

Some also claim GFCI breakers get more sensitive over time.

[Leecm3]

Thank you to everyone who has offered help! I am up and running!

There were three problems:

1. My drum filter screen needed to be cleaned a few times. Clay silt had it clogged and I was waiting to establish running water level before turning the drum on;
2. Variable speed pumps trip GFCI circuit breakers unless you have a particular Seimens breaker;
3. I still don't have enough water rushing into the drum unless I run the pipes on low. I wonder if my pond liner is getting sucked into or is bulging into the bottom drain gap. I have a pretty steep slope towards the BD. The only way for me to find out is to dive in and check the gap

Rather than taking a dip in a freezing pond, get a cheap camera than can be used under water attach it to pole such as a pool net telescoping pole and put in the pond around the BD. I did this when my air diffuser broke off from bottom drain to see where it broke. Below is one of the PICs I took.

[Nicoslam]

I run a Profidrum combi 30 with a sequence 8200gph pump. I have two 4" bottom drains and one 4" skimmer feeding gravity setup. on my system, if I throttle back any of the 3x 4" inlets, I run dry/low. One 4" aint enough. Add another inlet like a skimmer or get a smaller pump. Friction loss, hair algae, larvae and gunk buildup and age will only make this situation worse.