Prevent Pump Hose From Clogging


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I have a small pond which is about one meter in diameter and about 80 cm deep. The only fish are small guppies. Plants include a single night blooming lily and about a 70% cover of Pistia. The pump is rated 700 liters per hour and feeds a 5/8" garden hose which runs about three meters to a fountain which is about 80 cm above the pond surface. The fountain feeds a small but deep stream which runs about three meters into the pond. The stream is full of gavel which has, for the past ten years, served as a decent biofilter.

The pond water is crystal clear. No algae at all. The stream has some algae in shallow areas where the water moves slowly.

My problem is that the hose from the pump to the fountain has begun clogging up. I can clear it by simply disconnecting from the pump and blowing through it (strong lungs) or by using the garden hose. I have collected the debris which comes out. There is nothing but for tiny little particles of algae. After clearing, the fountain runs at full strength for about 12 hours and then begins to slow down. After three days it is at a trickle. The pump itself is free of debris and algae.

Any ideas what could be causing the clogging of the hose?
 
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Meyer Jordan

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I suspect what you are experiencing is a build-up of biofilm on the interior of your tubing. With a small pump this is a common occurrence, because the pump is not powerful enough to keep the biofilm sloughed off and of manageable thickness. I would recommend a larger pump.
 
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I thought it might be something like that.

I made a mistake on the OP. Here are the specs of my current pump:
  • Power: 25W
  • Head: 3.2m
  • Flow: 4000L/h

How large a pump do I need?

This replaced a 700L/h pump that I had when the problem first started.
 

Meyer Jordan

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I thought it might be something like that.

I made a mistake on the OP. Here are the specs of my current pump:
  • Power: 25W
  • Head: 3.2m
  • Flow: 4000L/h

How large a pump do I need?

This replaced a 700L/h pump that I had when the problem first started.

4000 lph is large enough, but 5/8" garden hose is much to small. At least 1" hose is needed for that size pump.
 
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Interesting. I had a ½" hose on it. I replaced it with the 5/8” hose last week and the clogging got much worse. From every three or four days down to every one or two. I was afraid that the hose was too big.

The way the pond is set up there is no way I can fit in a bigger hose. The pump outlet is ½“.
 
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http://www.aliexpress.com/snapshot/6089752783.html

When I first started this pond I used a 700L/h pump with a half inch hose. This worked fine for many years. I had to flush the hose once every three or four weeks. Infrequently enough that I could go on vacation without worrying about it.

Eventually the frequency of needed flushing fell to a week or two. I was advised to get a bigger pump. I did, but kept the same hose. Things got worse, with flushing required weekly.

I was advised to get a bigger hose. I did, and things got even worse, much worse. Now I need to clean it every other day.

It seems I was better off with the smaller pump and smaller hose. But, this makes no sense to me.

Would I be better off if most of the run was with PVC pipe rather than flexible hose? It would be difficult but not Impossible for me to do that.
 
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2015-05-05 16.56.42.jpg 2015-05-05 16.57.00.jpg 2015-05-05 16.57.16.jpg
3000 Words
 
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Very nice looking pond.:)

I would be surprised if your pump intake screen is not clogging up. You have a lot of plants that will contribute debris to the water column. When you went to a larger pump, the intake screen would just clog up faster.
Perhaps when you turn off the water pump to check the blockage, the backflow from the hose draining is clearing the pump intake screen so it only appears that the pump is clear when you pull it out of the water.
Do you have a separate filter system?
 
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I clean the pump intake every time I have to remove the hose to clear it. That used to be about once a fortnight, now it's every other day. I rarely find anything in the intake screen or inside the pump itself. There is a very slow buildup of algae on the intake screen. I remove this with a brush and hose. This only needs to be done once a month or so.

I removed a small amount of debris from the pond bottom yesterday. So, I expect to find stuff in the intake screen as I stirred things up quite a bit. I'll wait until the sun is higher and try to take some underwater photos before I remove the screen.
 
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filterscreen.jpg
The attempt at underwater photos failed. The GoPro fixed focus doesn't work at pond-distances. However, the filter screen was completely clear when I looked at it this morning. Here's how it looked immediately after removal. I scrubbed the algae off two weeks ago, so hardly any has grown back.

Removing and replacing it didn't alter the pump water flow at all.

The Pistia coverage varies. It multiplies very fast so eventually covers the entire pond except where the lily leaves are. I remove it to about 70% periodically and let it grow back.
 

Meyer Jordan

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View attachment 80757
The attempt at underwater photos failed. The GoPro fixed focus doesn't work at pond-distances. However, the filter screen was completely clear when I looked at it this morning. Here's how it looked immediately after removal. I scrubbed the algae off two weeks ago, so hardly any has grown back.

Removing and replacing it didn't alter the pump water flow at all.

The Pistia coverage varies. It multiplies very fast so eventually covers the entire pond except where the lily leaves are. I remove it to about 70% periodically and let it grow back.

Doesn't your pump have either a pad or foam prefilter?
 
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Good question. I'm convinced that Meyer is right about the biofilm. I'd never heard about it, but I've been doing a lot of reading. It seems to explain all the symptoms I've been experiencing. It would be great to know if there is some algecide would improve the situation. Of course, it would have to be something that is fish and plant safe.
 

Meyer Jordan

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Good question. I'm convinced that Meyer is right about the biofilm. I'd never heard about it, but I've been doing a lot of reading. It seems to explain all the symptoms I've been experiencing. It would be great to know if there is some algecide would improve the situation. Of course, it would have to be something that is fish and plant safe.

The is currently nothing on the market that is safe for use in a pond. Even if there was you would not want to use it for it would destroy the biofilm that is present on every other submerged surface in the pond. That you do not want to do.
As far as I know there is nothing on the market anyway that effectively (and permanently) removes biofilm other than sand-blasting.
I suspect, Ratsima, that the source of your problem is your guppies feeding on microorganisms that inhabit the rhizosphere of the Pistia. In the process they are breaking of tiny pieces of root which are eventually being drawn into the pump. These small organic particles are gradually being trapped by the biofilm in the piping, much like plaque accumulates in a human's arteries, eventually causing blockage.To solve this problem, this organic debris must be trapped before it enters the pump. This is why I inquired about the pre-filter. At present, you actually have no mechanical filtering, a must for any pond with fish.
 
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