Pool Total Dynamic Head Calculator - Complete Version
Trying to size your pool pump but having trouble calculating the total head? Use this pool total dynamic head calculator to work out the dynamic head for your pool and pump setup.
Pool Total Dynamic Head Calculator
If internal diameter is unknown, use external diameter as an approximation.
Pipe Friction Dynamic Head
This is not a straight-line measurement, but the actual length of the pipes and bends from the pool to the pump. Note that this calculator assumes that your pipes are made from PVC.
Pipe Fittings Dynamic Head
Elevation Dynamic Head
Total Dynamic Head: 0.00 m
What Is Total Dynamic Head?
When sizing a pool pump, you need to know 2 key things:
- Pump flow rate
- Total dynamic head
The pump flow rate is fairly straightforward and easily calculated, but the total dynamic head is more complicated and not well understood.
In essence, the total dynamic head (aka the pump head) is a measure of how much resistance the pump will face when sucking water out of your pool. This is not dependent on the pump itself, but on the pipework from the pool to the pump.
Longer, narrower pipes with lots of bends and fittings will have greater dynamic head than shorter, wider pipes with few bends and fittings.
If you have a larger dynamic head, you will need a bigger pump to get the same flow rate as someone with less dynamic head.
What Is The Formula For Total Dynamic Head?
The formula for total dynamic head is as follows:
Total Dynamic Head = Pipe Head Loss + Fittings Head Loss + Elevation Head Loss
Let's break each of these factors down a little further.
Pipe Head Loss
This is a measure of how much head loss there is as a result of friction in your straight sections of pipe. As water flows through pipes, it rubs along the pipe walls and experiences friction.
More water flowing faster through narrower pipes will generate more friction (and therefore head loss) than less water flowing slowly through wider pipes.
Longer pipe runs add more friction than shorter, more direct routes.
To minimise pipe head loss, consider widening the pipes between the pool and the pump. This will cost more in terms of plumbing, but could mean that you need a smaller pump and will save money on electricity in the long run.
The Hazen-Williams equation is used in this calculator to determine pipe head loss.
Fittings Head Loss
In addition to the friction occurring in the straight sections of pipe, there is also friction in your pipe fittings.
Each and every 90° elbow, ball valve, pipe union/coupling and tee section add to the overall head loss and create more resistance for your pump to work against.
Try to minimise the number of bends and other fittings in your pipework to reduce the head loss here. Widening the pipes (and therefore the fittings too) will also reduce this head loss.
Various types of fittings have associated 'K' values, which, when combined with the water velocity, are used to determine the fittings head loss. Higher 'K' values indicate greater head loss.
Elevation Head Loss
The final type of head loss contributing to your total dynamic head is elevation head loss.
This is simply the difference in elevation between your pool's water level and the pump's suction point.
The higher up your pump is relative to your pool, the greater the height that the pump has to suck up the water and therefore the greater the head loss.
The elevation head loss can be quite different for above ground and inground pools.
How Do I Use This Pool Head Calculator?
To use this calculator, you'll need to enter the following information about your pool, pump and its suction pipework:
- Length of pipe from pool to pump (in m)
- Pipe internal diameter (in mm)
- Pump flow rate (in litres per minute)
- Number and type of fittings in suction pipework
- Height of pump suction above pool water level
From this, the calculator will determine the total dynamic head for your pool and its plumbing.
Noticed any issues with this calculator? Please let me know over on the contact page.
A chemical engineer by trade, Louis is committed to debunking myths in the pool industry by explaining the underlying chemistry and making it accessible to all.