UV Light, what to expect?

[vestaviascott]

I don't have any food coloring around the house, so I'll need to remember to get some when I'm at the grocery next.

I did fill the pond up this morning and turned the pump off to observe. I could see slight movement of small specs of dust on the top of the water but it only goes around the perimeter of the pond, it does not travel out of the pond at any of the corners like I would expect if there was a leak there.

I'm suspecting that the leak or excess evaporation may be related to the upper basin area. Perhaps the fountain is splashing more water than it appears.

How long is it safe to leave the pump off in order to be certain the water level remains relatively constant with the pump and waterfall off?

 

[Meyer Jordan]

Fish load and age of pond are the influencing factors here. Turning off the pump stops any water flow through the biofilter. In your case this is presently the Mexican pebble bed. When this occurs Nitrification is then limited to the algae growth extant in the pond. In addition, the bacteria in the pebble bed will begin to die off due to lack of Oxygen.
As far as the welfare of the fish, 24 hours should not create a real issue and should be enough time to determine the source of your water loss. Just be aware that the biofiltration will take time to recover and you will likely see a rise in the Ammonia level. I would recommend that an Ammonia test be conducted after at least 12 hours. This will give you a better indication of exactly what level of biofiltration you have without the pump.

 

[vestaviascott]

Thanks Meyer. I understand what you are saying about the beach pebbles as biofilter. However, I do have the pump fully enclosed in a filter as well. See below. Does this filter not perform any biofiltration?

For ammonia testing, can you recommend an option there in terms of test strips or kits? I currently have a test strip kit that tests for free chlorine, alkilinity and PH. And are you saying to test after 12 hours of turning the pump off or after 12 hours of turning it back on after the leak test?

Finally, understanding that some level of evaporation is normal and to be expected, do you have a recommendation for a float valve refill mechanism?

 

[Meyer Jordan]

Thanks Meyer. I understand what you are saying about the beach pebbles as biofilter. However, I do have the pump fully enclosed in a filter as well. See below. Does this filter not perform any biofiltration?

Yes it does but it will not of much use when the only water movement will be generated by the swimming of the fish. You will be relying almost exclusively on the biofilm that has grown on the liner.

For ammonia testing, can you recommend an option there in terms of test strips or kits? I currently have a test strip kit that tests for free chlorine, alkilinity and PH. And are you saying to test after 12 hours of turning the pump off or after 12 hours of turning it back on after the leak test?

Get An API Master Test Kit.

Finally, understanding that some level of evaporation is normal and to be expected, do you have a recommendation for a float valve refill mechanism?

Since you have a submersible pump and no skimmer box, your only real option for a refill valve would be a Hudson float valve. The only proble, with tese is that they are almost impossible to hide and would really detract from the aesthetics of you pond.

 

[vestaviascott]

I've taken some measures to try to reduce water leakage from my fountain assembly (silicone sealant where the rubber coupling meets the aluminum rill joint). I'm monitoring the water level loss over time to determine if this is having a positive impact. Taking as many measures as I can before resorting to draining the pond or turning off the pump for an extended period.

Here is a photo of the water fountain outlet.

As you can see I've had to fabricate a plexiglass cover here in order to keep the water spout from overflowing the rill channel. The pump is flowing so fast (750 GPH) that the water spout here goes about 4 inches high if there is no cover plate here. Would it be advisable to install a ball valve in the line in order to throttle down the pump some to help avoid this?

Because of the overflow here, now minimized with the silicone sealant and the plexiglass cover (before now I just had a piece of heavy quartz tile sitting here acting as a baffle for the water force), the raw concrete blocks are acting like a sponge and soaking up water. The evaporation of the water from the porous concrete, I'm sure is comparable or perhaps even greater than that which occurs from the total surface area of the pond. So, minimizing that loss, I believe, may be key to keeping the water level as stable as possible.

I suspect that once I get the blocks sealed (mortared in and skim coated), there will still be some soaking and evaporation from this structure, but not as much as from the raw blocks as they now sit.

 

[Meyer Jordan]

Unsealed concrete, especially concrete blocks, have the capacity to wick a sizeable quantity of water. I would venture to say that is where you will find your greatest water loss.

 

[vestaviascott]

Unsealed concrete, especially concrete blocks, have the capacity to wick a sizeable quantity of water. I would venture to say that is where you will find your greatest water loss.

I think you are right.

It sounds like a good setup for an experiment.

I'm going to do a test just to confirm the impact of evaporation from the unsealed blocks in the fountain basin.

I'm going to get two 5 gallon buckets and fill them with about 2 inches of water each. In one I'm going to place a concrete block the same as I'm using for my fountain wall. In the other, just the water. I'm going to set them on my patio and check the water remaining in each after a day.

I'm going to benchmark after an hour to measure the levels to see how much water the concrete block has already wicked up before any significant evaporation has had time to occur in either bucket of water.

 

[Lisak1]

Hmmm... I think a submerged block will only absorb so much water. Your exposed blocks have the ability to both absorb on the pond side and then allow for evaporation on the "land" side, which would account for a greater amount of lost water. Am I thinking about this right?

 

[vestaviascott]

Hmmm... I think a submerged block will only absorb so much water. Your exposed blocks have the ability to both absorb on the pond side and then allow for evaporation on the "land" side, which would account for a greater amount of lost water. Am I thinking about this right?

Not exactly.

To simulate the same conditions as the pond, there is only enough water in the bucket to cover about an 1.5 inches of the block, just like what happens in my fountain basin.

Its obviously not lab conditions controlled experiment, but the setup should be sufficient to give a ballpark idea of the contribution to evaporation that the raw concrete blocks make over standing water not wicked by block.

 

[vestaviascott]

Update: After about a half hour, the concrete block wicked up about a quarter inch of water from the bucket. The pitcher below was filled to the bottom of the yellow dot for each bucket. You can see the water level of the blue concrete block bucket when poured back into the same pitcher.

 

[Meyer Jordan]

Hmmm... I think a submerged block will only absorb so much water. Your exposed blocks have the ability to both absorb on the pond side and then allow for evaporation on the "land" side, which would account for a greater amount of lost water. Am I thinking about this right?

Yes, because this block is porous, any water that is wicked above the waterline is subject to evaporation. On a hot, sunny day this evaporation rate will be quite high due to the higher (and faster) heat absorption of the block over the water.
A concrete block will certainly only wick to a certain height, but because of the evaporation rate will continuously wick. With the use of unsealed concrete blocks in contact with the pond's water column, the total water surface area subject to evaporation is increased by the blocks.

 

[Lisak1]

there is only enough water in the bucket to cover about an 1.5 inches of the block

Ah! I misunderstood your experiment - I thought the block would be completely under water.

 

[Angel]

@Meyer Jordan may correct this but if the concrete is wicking as more surface are is exposed to sun more will evaporate

 

[Meyer Jordan]

@Meyer Jordan may correct this but if the concrete is wicking as more surface are is exposed to sun more will evaporate

Correct. See Post #41 in this thread.

 

[vestaviascott]

Update: My unscientific experiment provided some unexpected results. After appx 24 hours, the amount of water evaporation in both buckets was virtually nill.

Perhaps the 5 gallon buckets are not conducive to evaporation.

Anyway, rather than waste much more time on that, My next phase test is to disconnect the fountain and allow the pump water to go directly into the pond, bypassing the upper rock basin altogether.

For the period of 24 hours between yesterday and today, the pond lost 1.75 inches of water. That's appx 40 gallons of water lost in a 24 hour period. Definitely not sustainable!

I'm going to measure the same between now and tomorrow with the bypass in place.