What does "Max Head" mean? Stupid question...

[Lance M.]

I guess I'm being stupid but what does max head mean with regards to return pumps?

Like what does a pump rated at 500gph with a 10ft max head mean?

 

[Toirtis]

It means your head is too big.

'Max head' refers to the maximum height the pump can pump to....for instance, the max head on any particular pump might be 10', but you will have very little flow at that height, but it still will give some flow...most pumps have a graph on the side of the box that will give you an idea of flow rate at any given head height.

For instance, my QuietOne 3000 pumps 3000l/h at a head/height of 0', but at 5' pumps 1000l/h, at 8' pumps about 10l/h, and 0l/h at 9'.

 

[tecwzrd]

It has to do with gravity and the pressure of gravity against the pump and it's ability to go against the pressure. Typically with aquariums you have a 4-5 foot distance from your sump to the top of the tank and a pump like the Mag 5 that can produce 500 GPH without any pressure will only produce 250 GPH with 5 feet of pressure against it.

If you were trying to power a waterfall in an outdoor pond that was 8 feet up you can see you would need a pretty powerful pump to get the water up or else you would have very little flow.

Also each 90 degree bend in plumbing (using PVC for example) counts roughly as 1 head pressure. Each 10 feet of horizontal piping reduces 1 head also.

So to sum up if you have a tank with a 600 GPH overflow and you have 4 90 degree bends and your sump is 4 feet below the tank to get close to 600 GPH flowing through your tank you would need a pump that is rated at 600 GPH with a 8 foot head (like the Mag 9.5).

It's better to buy a slightly stronger pump and slightly restrict the flow using ball valves (if it can handle it) or T off the return to have some go back into the sump or a fuge.

 

[Lance M.]

It means your head is too big.

LOL. Do you still have like 50 bichirs?

Ok well the graph on the side of the box really doesn't help if your shopping online .

So basically a pump rated at 500 gph with a 10ft max head will pump 500gph at 0ft and 0gph at 10ft? (not really 0 but low) and 250gph at 5ft? vertical with no bend?

I'm asuming it's a log graph (flow to head) so it wouldn't be 500->0ft,450->1ft, etc. like a line graph.

Would a 45 degree bend be half a head?

Is there an equation or something to calculate the flow at each ft?

Am I thinking about this too much, and should I just go to the store and look at the graph on the side of the box?

 

[tecwzrd]

Don't assume head height for any pump, they all preform differently which is why there isn't a standard formula that works for all pumps. You can calculate for head loss though.

Most online retailers will list head height pressures for each type of pump (like the ones I listed in bold). If the particular site that you want to buy from doesn't list it plenty of others do or you can get it from the manufactures site.

45 degree bends take about 4 to equal 1 heads difference. If you use vinyl tubing with arches versus bends there is very little pressure against the pump.

As I said before it's best to get a rough idea of how large a pump you need and buy a slightly larger one and T off the return to go back into the sump/fuge. That way you won't put any pressure on the pump and can easily control the flow back to the tank. See photo below (which is a link) as an example.

 

[Lance M.]

Ok. I think I get it now. Thanks for help. The picture helps.

Lol. Does the water look purple...?

 

[tecwzrd]

No it's just full of Chaetomorpha Algae for nutrient exportation in that photo.

 

[Lance M.]

I know the refugium has the chaeto, but in the return section on the left next to the refugium the water looks purple.