Pool filtration

Introduction

Our pool is 40ft x 20ft and contains around 40,000 gallons of water. Living in Indiana, USA, the pool is opened in May but has to be closed in October, sometimes even as late as November, depending on how cold it gets.

There all sorts of pool forums around to ask for help and advice or even just show off a pool. Some people in thoe are obsessed with testing the chemical levels, are plagued by various algae problems, and confused by the various pump, filter and vacuum systems.

In order to be keep it clean and santized we use a simple sand filter and chlorinator system. A multiport valve controls the water flow around the system.

The Setup

Some other pool plumbing

Compared to some (see above images which were taken from the internet) our pumping, filtration, and chlorination setup is fairly compact and simple. This is not a criticism of the above setups, they may have a spa, bottom of the pool draining system, water jet, fountain etc. that need the extra plumbing.

Our pool plumbing

The pump pulls water from the pool's skimmer, puts it through a pre-pump filter then, in normal operation, into the sand filter. From there it goes through the chlorinator and out to the pool's outlet. Another pipe, for use when the filer valve is set to backwash, rinse, or waste, carries the water out of the system.

Hayward Vari-Flo Multiport Valve

There are several models of this valve available, including the SP0714TC, SP0714TE, SP0714T, SP0715A, and SP071621. They all work the same way; a handle allows a choice of what you want done, this includes filtering (the normal position), backwashing, rinsing, to waste, and recirculating.

The positions are:

Valve Setting	Flow	Function
Filter	Pump - Sand Filter (top) - Return (bottom)	For normal filtration and vacuuming
Backwash	Pump - Sand Filter (bottom) - Waste (top)	For cleaning the filter
Rinse	Pump - Sand Filter (bottom) - Waste (top)	For clearing valve of debris after backwashing
Waste	Pump to waste	For vacuuming directly to waste, lowering pool level and/or draining the pool
Closed	No circulation	For shutting off all flow to filter and pool
Recirculate	Pump tp pool	Bypass the filter and simply return the water to the pool

Hayward S200 Sand Filter

As with most sand filters, water is forced downwards through the sand, collected at the bottom and then back out. Backwashing is the process of cleaning the debris collected out of the sand. Water is forced up through the sand, it and the debris collected are then discharged out to waste. Rinsing the filter means reurning the water to its normal filtering flow, but discharging it to waste, which also removes any disturbed debris.

The state of the discharged water can be seen in the sight-glass or glass bottle attached to the side of the Vari-Flo Multiport Valve. When backwashing, this water can be very durty and needs to be run until it is clear. I find it takes a minute or two every couple of days. Rinsing is much quicker, usually less than a minute.