Restricting Pump Flow

[denniswiseman]

I have a spare pump that is to large for my sand filter.
What's the general opinion of restricting the pressure side of the pump to reduce flow through the filter

 

[jblizzle]

Generally should be ok assuming not too much restriction. I would suggest a larger filter, although I have not checked if it is proper for your pool size.

 

[denniswiseman]

My filter is fine for my 45000 litre pool with a rated flow of 10 cubic metre
With a heavy use of 60000 litres and a light use of 100000 litres

 

[mas985]

How did you come to the conclusion that your pump was too large for the filter?

 

[denniswiseman]

The filter spec says .6hp with a flow of 10 cubic metres
The pump is 1hp with a flow of 17 cubic metres
Plus the fact that it was not filtering that well even with DE in the filter

 

[chiefwej]

Sounds like you are a candidate for a VS pump. Slower flow and less pressure=better filtration. My neighbor just installed a VS pump and he can't believe how much better his sand filter works. He still needs the higher speeds of his infloor cleaning system and the solar heater.

 

[mas985]

The filter spec says .6hp with a flow of 10 cubic metres
The pump is 1hp with a flow of 17 cubic metres
Plus the fact that it was not filtering that well even with DE in the filter

Specs mean nothing for operating points. Typically those are maximum flow rates. The actual operating point could be much less than those values. Do you have a head curve for the pump?

Also, when you say it is not filtering well, what exactly are you seeing/experiencing?

 

[denniswiseman]

Dirt was coming back into the pool even with DE in the filter
I had also done a deep clean

 

[mas985]

That sounds more like something is wrong with the filter. Was DE coming back out of the filter? If the flow rate was too strong, you would probably see DE coming out of the returns.

How much was the pressure rise when you added DE? It should be 1-2 PSI.

 

[denniswiseman]

It's been a while because I changed it for a smaller one which worked fine and the pressure rise was 2

 

[mas985]

Is this the pump?

Power-Flo II 

That is not a very powerful pump. In fact is usually used for AG pool even though it is self-priming.

 

[denniswiseman]

No that's not the one but the smaller .5hp is the one that I replaced it with
My superflo filter Q120 is the right size for my 45,000 litre (10k UK gallons) pool
The pump I changed for the smaller one is FCP-570S. You can click on the link to get the technical data

 

[mas985]

Ok, I am really confused by what you are saying. Let's start over.

What is the pump make/model that you think is producing too much flow rate?

Also, what is the filter pressure with that pump?

What is the relative height the filter gauge with the pool water?

What is the diameter of most of your plumbing?

 

[denniswiseman]

Ok, I am really confused by what you are saying. Let's start over.

What is the pump make/model that you think is producing too much flow rate?

Also, what is the filter pressure with that pump?

What is the relative height the filter gauge with the pool water?

What is the diameter of most of your plumbing?

1 The original pump was the Gibbons FCP-750S
2 I don't remember
3 The filter gauge is about 6" higher than the water level

4 I have re-plumbed it with Flexpipe which has an ID of 42mm OD 50mm

 

[jblizzle]

that does not look like a very small filter as far as diameter is concerned.

 

[mas985]

Ok so you are using the smaller pump now?

What is the concern now with the smaller pump because that is a really small pump and I doubt it is exceeding the flow rate specification.

Is the smaller pump still blowing dirt into the pool? If so, more than likely that is a problem with the filter, not the pump.

What will you be doing with the larger pump?

 

[denniswiseman]

that does not look like a very small filter as far as diameter is concerned.

If you look at my post about the filter. you will see it's the smallest one .24m (about 2.6 square feet) which is more than adequate for my pool

 

[denniswiseman]

Ok so you are using the smaller pump now?

What is the concern now with the smaller pump because that is a really small pump and I doubt it is exceeding the flow rate specification.

Is the smaller pump still blowing dirt into the pool? If so, more than likely that is a problem with the filter, not the pump.

What will you be doing with the larger pump?

Yes I'm using the smaller pump now. The only concern I have is that it shows some signs of leaking and when I send it back I will need another pump to keep up the circulation. I have another post on here about that. That was why I was enquiring about restricting flow
The smaller pump filters fine.
Because the pool is covered I get very little blown debris, mostly the fine dust through normal chlorine sanitation

 

[mas985]

Ok if the smaller pump works fine but the larger pump blows debris through the filter, then you could use a valve on the return side of the pump to reduce the flow rate some. You could also downsize the impeller if you plan on using it longer.

 

[denniswiseman]

Ok if the smaller pump works fine but the larger pump blows debris through the filter, then you could use a valve on the return side of the pump to reduce the flow rate some. You could also downsize the impeller if you plan on using it longer.

Thanks for your time spent on this with me trying to understand my setup
I was primary concerned with any detrimental effects of restricting the flow but the usage depends on what the supplier says about my leaking Powerline. I will also contact the supplier of the larger pump and see if they have a smaller impeller that is interchangeable