How long does the pump really need to run?

[Anonymous [GDPR] European in the UK]

Many thanks for that Mark, Chart saved for future reference.

What you have said about cartridge having the lowest head loss is what I was expecting. As you say the internal fittings are where the head loss occurs which is why I said the "designers" are lazy etc because it could easily be improved and needs to be given that we are going Eco. I have fitted a 15 PSI gauge to my filter as I needed to see the 2 PSI I run at also. I notice the almost exponential graph as the flow increases, which fits with my empirical data and is where I am investigating the head loss. Is it through the media or bad plumbing? Not an issue in the past as a powerful pump always makes sure the water gets where it's going but reducing the power brings on new challenges.

Thanks for you help on this, it's appreciated.

Regards
John

[Anonymous [GDPR] European in the UK]

Having had a chance to look over the data from your table Mark. If you look at the TR140 sand filter with 2" multiport and compare it with the TR50 or 60 with 2" multiport, the additional filter media in a TR140 which holds nearly three times what a TR60 and even more than that in a TR50 yet it has the lowest headloss figures same thing with the TR100 so it isn't the filter media causing the headloss it's poor hydraulic design with the laterals. This is the area I am concentrating on at the moment.

Thanks again for the data.

Regards
John

[mas985]

Head loss in a fixed plumbing system follows the pump affinity equations where head loss is proportional to the square of the flow rate. This is why any plumbing system can be fit to a plumbing curve that follows this equation:

Head Loss (ft) = Cp * GPM ^2

Where Cp is the plumbing curve constant. Typical 2" plumbing has a curve constant that is close to 0.0082 while 1.5" plumbing is closer to 0.0167.

This is useful when trying to determine the operating point of a new pump on an existing plumbing system. You just have to draw the plumbing curve over the pump's head curve and where they intersect is the new operating point.