by Rob Cox, Sept 5, 2019
When you go shopping for sand pool filters, the first thing you may notice is that you can buy sand filters with the backwash valve mounted on the top of the tank, or with the valve mounted on the side of the tank.
The second thing you notice is that the side-mounted sand filters are more expensive than those with top-mounted multi-port valves. And if you were especially observant, you may notice that top mount is more common for very small sand filters, especially those used on above-ground pools, and side-mount is more common on the large sand filters, used on large community pools.
Why are there two types of sand filters? As though the world wasn't complicated enough!
Top mounted sand filters are always sold with a multiport valve that is flange attached to the top of the filter tank. Top mount sand filters also include all internals (Standpipe, Hub, Laterals), and the drain assembly. Top mount sand filters are cheaper for manufacturers to make, because the top-mount design is simpler, and much fewer parts are used.
For many above ground pools, sand filter systems include a top mounted sand filter, and a pump mounted on a skid. For most above ground pools with sand filters, this arrangement makes the most sense, and for several reasons, a top mounted sand filter may be the best choice.
Top mounted valves can also provide higher flow rates when sufficiently upsized, and when a 2" multiport valve is used.
Side mounted sand filters are sold separately from the valve, a multi-port or slide valve, primarily because you have a choice. A slide valve (aka push-pull valve) offers only two functions, filter or backwash, but can be preferred because of (much) lower resistance than a multiport valve, and because the simple design requires fewer repairs.
Side mount filter tanks also let you inspect the sand or change the sand a bit easier than top mounted filters, which requires that the valve be detached from the filter tank to gain access to the sand or internal parts.
Side mount filters can allow you to optimize savings with a variable speed pump, when used with a slide valve. Side mounted valves are also a bit easier to operate, and easier to plumb, being closer to the ground.
More important perhaps than sidemount valve vs. topmount valve is the SIZE of the sand pool filter. Larger sand filters operate with much higher flow rates and lower pressure than smaller tanks. Small sand beds also spoil and need replacement much faster than a sand pool filter that is sufficiently over-sized sand filter.
Using that logic, the best strategy may be to save the money that you would spend on a sidemount filter, and use it to buy a larger top mount filter, with a 2" top mounted multiport valve. For most inground pools, this would be the 27" or 31" tank diameters, and for most aboveground pools, a 22" to 24" tank diameter.
Thanks for Reading!