Hello Dale,
My name is Pamela Russell and I am the President of Russell Watergardens & Koi - we manufacture Hydro Dynamax pumps. You mentioned that you purchased an HD4700 3 years ago and have some questions. I would like to help you out if I can.
Based on the size of the skimmer inlet that you described, the HD4700 pump is not oversized. We use a couple of factors to determine the proper range of pump flow rate for a pond:
1. The water should be passed through the biological filter at least once every two hours. With a 3,000 gallon pond, the minimum pump size for you is about 1,500 gallons per hour. More flow is also ok.
2. The pump flow rate should also be chosen in order to give you the waterfall effect that you desire. Smaller pumps are used for a smaller flow and larger pumps for a stronger flow, etc.
You must take into consideration the total head loss (vertical and horizontal distance the water will be pumped, as well as pipe diameter). (With an Aquascape system you probably have 2" pipe which is ideal for the HD4700.) For example, if your vertical pumping height is 5' and your horizontal pipe run is 18', you would have just under 7' of head. The flow rate of the HD4700 is around 4,300 gallons per hour at 7'. If you care to provide your actual numbers, I would be happy to calculate the head for you.
The surging that you described (pump on, then pump off, then pump back on again) is commonly caused by the automatic float switch on the HD pump fluctuating with the water level. The float will lower in accordance with the water level until it reaches a point where it turns the motor off in order to protect it from overheating in a low water situation. Once the pump turns off, water that is in transit (in a waterfall or stream) will travel via gravity into the skimmer where it will raise the water level. The float then rises as well and allows the pump motor to turn on again. The water level in the skimmer is again lowered when water fills the stream/waterfalls area. So you can see, you end up with the surging pattern you described. This is caused by not having enough water in the pond.
I would suggest some things to look for within your system:
1. Make sure your water level is not low. In your skimmer, there is an overflow port where excess water exits when the water level is too high. The water level is correct when it is exactly at the lower edge of that overflow port. If it is not up to that level, add water to the pond. Continue adding water until the level is even with the bottom of that overflow port with pump running. Now your pond is full.
2. Verify that there is nothing blocking the intake of the skimmer. From time to time we see a plant, a rock, or piece of wood, decorative item, etc. that lodges partially in front of the skimmer inlet and prevents the full flow of water from entering the skimmer.
3. Make sure the skimmer net and pad are kept clean. If either of these become too full of debris, it can reduce the flow of water to the pump, which could cause the water level in the skimmer to decrease and the pump to turn off.
You mentioned that your HD4700 pump failed last week. I would like to offer the help of our Customer Service Associates at (800) 844-9314 to troubleshoot to see if there is any remedy that you can make there on site. If not, we may be able to repair the pump for you.
I hope this information has been helpful. I welcome your comments (and the comments of others).
Thank you!
My name is Pamela Russell and I am the President of Russell Watergardens & Koi - we manufacture Hydro Dynamax pumps. You mentioned that you purchased an HD4700 3 years ago and have some questions. I would like to help you out if I can.
Based on the size of the skimmer inlet that you described, the HD4700 pump is not oversized. We use a couple of factors to determine the proper range of pump flow rate for a pond:
1. The water should be passed through the biological filter at least once every two hours. With a 3,000 gallon pond, the minimum pump size for you is about 1,500 gallons per hour. More flow is also ok.
2. The pump flow rate should also be chosen in order to give you the waterfall effect that you desire. Smaller pumps are used for a smaller flow and larger pumps for a stronger flow, etc.
You must take into consideration the total head loss (vertical and horizontal distance the water will be pumped, as well as pipe diameter). (With an Aquascape system you probably have 2" pipe which is ideal for the HD4700.) For example, if your vertical pumping height is 5' and your horizontal pipe run is 18', you would have just under 7' of head. The flow rate of the HD4700 is around 4,300 gallons per hour at 7'. If you care to provide your actual numbers, I would be happy to calculate the head for you.
The surging that you described (pump on, then pump off, then pump back on again) is commonly caused by the automatic float switch on the HD pump fluctuating with the water level. The float will lower in accordance with the water level until it reaches a point where it turns the motor off in order to protect it from overheating in a low water situation. Once the pump turns off, water that is in transit (in a waterfall or stream) will travel via gravity into the skimmer where it will raise the water level. The float then rises as well and allows the pump motor to turn on again. The water level in the skimmer is again lowered when water fills the stream/waterfalls area. So you can see, you end up with the surging pattern you described. This is caused by not having enough water in the pond.
I would suggest some things to look for within your system:
1. Make sure your water level is not low. In your skimmer, there is an overflow port where excess water exits when the water level is too high. The water level is correct when it is exactly at the lower edge of that overflow port. If it is not up to that level, add water to the pond. Continue adding water until the level is even with the bottom of that overflow port with pump running. Now your pond is full.
2. Verify that there is nothing blocking the intake of the skimmer. From time to time we see a plant, a rock, or piece of wood, decorative item, etc. that lodges partially in front of the skimmer inlet and prevents the full flow of water from entering the skimmer.
3. Make sure the skimmer net and pad are kept clean. If either of these become too full of debris, it can reduce the flow of water to the pump, which could cause the water level in the skimmer to decrease and the pump to turn off.
You mentioned that your HD4700 pump failed last week. I would like to offer the help of our Customer Service Associates at (800) 844-9314 to troubleshoot to see if there is any remedy that you can make there on site. If not, we may be able to repair the pump for you.
I hope this information has been helpful. I welcome your comments (and the comments of others).
Thank you!