Hayward ProSeries Side-Mount Sand Filter

This is the ProSeries with its valve on the side of the tank instead of on top. The tank has a domed lid on top, held by a clamp, and the sand goes in and comes out through there. The valve never has to come off to change it. An owner asked what the side-mount S310S gains over the top-mount S310T2. Hayward's support team named exactly that: ease of service. Otherwise, it said, the two work the same.

Two sizes are current, 24 and 30 inches, and the 24-inch comes three ways, by the valve in the box. Hayward lists all of them for in-ground pools. Answering an owner on the S244S page, its support team said the 24-inch would also work fine on an above-ground pool with a 1.5 HP pump.

Which valve comes with it

• S244S — the 1½ in. VariFlo, SP0710X62
• S244SV — a 2 in. slide valve, SP0410X602S, which glues onto the pipe
• S244SLV — no valve
• S310S — no valve. Hayward's support team names the 2 in. VariFlo, SP0715X62, for it

The sell sheet lists those same three valves as the ones to order for the valveless models.

The VariFlo on this filter has six positions: Filter, Backwash, Rinse, Waste, Recirculate and Closed. That is one fewer than the seven-position VariFlo XL on Hayward's top-mount ProSeries, which is a different valve with its own part number. The slide valve has two positions, filter and backwash, and no rinse.

The flow rating and the pipe

Hayward rates the S244S at 62 GPM and the S310S at 98 GPM. Both are 20 GPM per square foot of sand, which the sell sheet calls the maximum NSF rating. Asked whether 62 was the best rate or the most, Hayward's support team said it is the design flow rate, and the filter tolerates more and works at less.

The owner's manual sets a separate limit on the pipe:

• 1½ in. — 45 GPM
• 2 in. — 80 GPM
• 2½ in. — 110 GPM

So a 24-inch plumbed in 1½ in. pipe on the 1½ in. valve is limited by the pipe, not the sand, well short of 62. The manual's head-loss chart for the 1½ in. multiport shows why that matters. It reads about 14 feet of head at 40 GPM, about 21 at 50 and about 31 at 60, and the curve keeps steepening. To use the 24-inch's full rating, the plumbing and the valve need to be 2-inch.

The 30-inch outruns even that. Its 98 GPM is more than the 80 the manual allows 2 in. pipe, and 2 in. is the largest valve Hayward offers for it. On 2-inch plumbing, the S310S runs below its rating. Work out what your pump actually moves before choosing between them.

Loading the sand

The 24-inch takes 300 lb and the 30-inch 500 lb of No. 20 silica sand, graded 0.45 to 0.55 mm. Hayward's support team has said it recommends only No. 20 silica pool filter sand in its sand filters, and turned down a polyethylene fiber media when an owner asked.

It all goes in through the top:

1. Lift off the top diffuser and move the flexible automatic air relief tube to one side, inside the tank.
2. Cap the diffuser elbow pipe with the sand shield, so no sand goes down it.
3. Check the drain cap is on, then fill the tank about halfway with water. The water cushions the sand as it lands, which protects the laterals.
4. Check every lateral is in the down position.
5. Pour the sand, and level it about 6 inches below the top of the tank. Use no more than the recommended amount.
6. Take the shield off, put the diffuser back with the air tube through its hole, wipe the flange clean, and seat the dome with its o-ring. Tighten the clamp with a screwdriver while tapping around it. Do not overtighten.

The 6 inches is not the top-mount's number. That manual has its sand at least 10 inches below the top.

Starting it up

Open the manual air relief on the dome fully before the pump starts, and leave it open until a steady stream of water comes out. Every suction and return valve has to be open too.

1. With the pump off, press the VariFlo handle down and turn it to Backwash. Always press it down before turning it; that protects the valve seat.
2. Prime and start the pump.
3. Once water runs steadily out the waste line, run it for at least 2 minutes. That flushes fine particles out of new sand.
4. Pump off, Rinse until the sight glass runs clear, about half a minute to a minute.
5. Pump off, Filter, pump on. Write down the gauge reading. That is your clean pressure.

On a new plaster or gunite pool, or anywhere with a lot of plaster dust, start in Filter rather than Backwash, so the dust does not clog the laterals from below.

Backwash at 6 to 8 psi over clean

The side-mount manual says to backwash when the gauge reads 6 to 8 psi above the clean reading. It says so twice, in the start-up steps and again under the valve positions. That is 2 psi sooner than the 8 to 10 in Hayward's top-mount ProSeries manual, and in its general knowledge base answer about high filter pressure. On this filter, go by this filter's manual.

1. Pump off. Handle to Backwash.
2. Pump on, and run until the sight glass is clear, about 2 minutes or less.
3. Pump off. Handle to Rinse, pump on for half a minute to a minute.
4. Pump off. Handle to Filter, pump on.

The pump goes off before the handle moves, every time. The manual says it is to spare the piping and valves the strain. The full backwashing guide covers the rest, including what to do with the waste water.

Expect to backwash often while a new pool is cleaning up. The manual warns that the first dirt load is unusually heavy.

Air in the filter

The side-mount has two ways of dealing with air. An internal tube, which Hayward calls automatic air relief, purges trapped air while it runs. And there is the manual relief valve on the dome, under the gauge.

Hayward's support team says to bleed the air out any time the plumbing has been opened, which includes cleaning the pump basket. An owner who got a rush of air out of the filter when shutting down to clean the basket was told to look for a leak on the suction side, starting with the pump lid.

The manual's safety rules for the relief valve are strict. It must be open, with every control off, before anyone services the system. The system must never run or be tested above 50 psi. And it must never be purged with compressed air; for blowing out lines, only a low-pressure blower under 5 psi.

Pressure and heat

The 50 psi limit has a temperature attached. The manual's chart keeps the S244S and S310S at 50 psi up to about 100°F. Above that the line slopes down, to about 25 psi at 150°F. A pool stays well under 100°F. A spa at 104°F sits just past the point where the line starts to fall.

Winterizing

Three steps from the manual:

1. Take off the drain cap at the base of the tank and leave it off all winter.
2. Press the VariFlo handle down and park the pointer between two positions, so the valve drains.
3. Winterize the pump by its own instructions.

Hayward's support team says there is also a plug and a screen behind the drain cap. Keep all of it somewhere you will find in spring.

What changed in 2024

Hayward's parts diagram lists two filter internals retrofit kits. It gives them as SX244MA1S for an S244S made before 07/24 and SX310MA2S for an S310S made before 07/24. The current manual describes the same two numbers as the lateral holder, the bottom vertical pipe and the bottom elbow in one assembly. And it lists the elbows as coming with a new air tube.

Hayward does not spell out what changed beyond the air tube. What it does say is enough to act on. On an older tank, the retrofit kit is the number to give a dealer when the underdrain goes, rather than elbows or an air tube on their own. If you are not sure when yours was made, the serial number tells Hayward: its support team read one owner's manufacture date straight off it.

Getting at the laterals

Take the clamp and dome off the top. The valve stays plumbed in. The lateral holder is what Hayward calls an umbrella-fold design, and the sell sheet credits its folding joint with easy access to the laterals. Hayward's support team says the bottom vertical pipe is a press fit into the bottom elbow, not glued.

The laterals themselves come only in packs of ten: SX240DNRPAK10 for the 24-inch and SX310HNRPAK10 for the 30-inch. A cracked one shows up as sand on the pool floor.

If it cycles short or won't clear

The manual's troubleshooting table covers three problems:

• Low water flow. Check the skimmer and pump baskets, check the intake and discharge lines for restrictions, look for an air leak on the intake side, which shows as bubbles at the returns, and backwash.
• Short filter cycles. Look for algae and shock if needed, and bring chlorine and pH into range. Then check the top of the sand for crusting or caking, and remove an inch of it if you find any.
• Water won't clear. Check chlorine, pH and alkalinity, make sure there is enough flow through the filter, run it longer, and confirm the valve is on Filter.

How long the sand lasts

The manual gives no figure. Hayward's support team, answering on the S310S page, said to replace the sand generally every 3 to 5 years. It lasts longer if the water stays clear, and less if you keep having to backwash to hold the pressure in its normal range.

Check the prefix before you buy

• S244S, S244SV, S244SLV and S310S — Expert Line, sold through dealers. Three years parts and one year labor on an in-ground pool.
• W3S310S — Open Line, approved for online sale. One year parts, no labor.

On this filter the difference is two years of parts and a year of labor, not a trim change. A W3 filter is a sanctioned purchase, not a gray-market one. The Hayward brand page explains the two channels.

Older and bigger side-mounts

The S210S, 21 inches, is on the 2017 sell sheet at 2.20 sq. ft., 44 GPM and 200 lb of sand, and it is gone from Hayward's current listings. Its elbows and lateral holder are still on the diagram. Its line on the manual's temperature chart starts dropping in the low 70s, well before the bigger two.

An old S-240 or S200. Hayward's support team suggested the S244S to replace an S-240. It said the S244SV would not drop straight in for an S200, but the plumbing changes should be minimal.

The 31 and 36-inch side-mounts are the ProSeries Plus, a separate series with its own manual, and they are not covered here.

Where Hayward's documents disagree

• The dome. The manual's parts table gives the top closure dome as SX200Z5. Hayward's diagram gives SX200Z5 as the small o-ring under the air relief cap, and the dome as SX244K, which is also what its support team told an owner. This page uses SX244K.
• The 2 in. valve. The manual prints SP715X62. The sell sheet, the diagram and Hayward's support team all write SP0715X62.
• The backwash point. 6 to 8 psi in this manual, 8 to 10 in the top-mount manual and the knowledge base.
• The air relief. The sell sheet lists a manual air relief. The product pages describe an automatic one. Both are on the filter: the relief valve on the dome and the air tube inside.
• The air tube parts. The diagram lists SX200Z1 and the SX200Z2 lock screw. The 2024 manual lists new tubes with locknuts, SX244AT and SX310AT.
• Filter area. The manual rounds the 24-inch to 3.1 sq. ft. and the 30-inch to 4.9. The sell sheet and product pages give 3.14 and 4.91.
• The valveless pages. The S244SLV and S310S product pages list the six-position VariFlo among their features, though neither comes with one.