Astral filters have a habit of turning up without a model badge. The decal weathered off a decade ago, the manual went with the previous owner, and what is left is a fibreglass or polymer tank, a lock ring, and a valve that has started passing sand back to the pool. The parts are all still available — the problem is working out which ones.
This guide is organised around that problem. It covers the families you are most likely to meet on a pad — Astramax, Cantabric, the Millenium and Millenium Series 2000, Terra, Persius and the CEL commercial tanks — and gives you the measurements to take when the badge is gone, because on these filters the dimension is the part number.
Telling the families apart
| Family | Tank | Valve position | Lid and closure | Typical sizes |
|---|---|---|---|---|
| Astramax | Blow-moulded polymer, one piece | Top mount | Clear or opaque lid in a threaded lock ring | Domestic |
| Cantabric | Laminated fibreglass, smooth | Top or side mount | Lid with a separate valve lock ring | 19in to 30in |
| Millenium / Series 2000 | Polymer, ribbed | Top mount or side mount | Clamp kit around a flanged lid | Domestic |
| Terra (2500 series) | Polymer | Top mount | Lid and locking ring as one assembly | 50, 100, 150 |
| Persius (1800 series) | Fibreglass | Top mount | Valve lock ring | Domestic |
| CEL 30 / 50 / 70 | Commercial laminate | Side mount | Bolted or clamped | Commercial |
Model coverage in our catalogue sits on the Astramax, Cantabric Series 3000, Millenium and Millenium Series 2000, Terra 50, Terra 100, Series 1800 Persius, and the CEL 30 and CEL 50 commercial tanks.
Opening the tank without breaking it
Astral internals are glass-filled polymer that has spent a decade wet and hot, and most of the damage done to these filters happens during the repair rather than before it.
Pump off at the breaker, valve to closed or to the winter position, and both isolation valves shut. Open the air relief and let the pressure off before you touch the lock ring — a ring released under pressure is the most common serious injury on a pad. Pull the drain plug and let the tank empty properly; wet sand weighs roughly 1.6 times what dry sand does, and a 24-inch tank holds enough of it to make the difference between a job and an injury.
With the valve off, the standpipe is what holds the assembly central. Tape the open top of the standpipe before you shovel. Sand that gets into the pipe ends up in the laterals, and from there it goes to the pool the first time you run the filter — which looks exactly like the fault you just repaired.
Shovel or wet-vac the sand out down to the lateral hub, then work the arms free by hand rather than levering them. If an arm will not unscrew, it is already cracked at the root; note it and replace the set. Lift the standpipe and hub out as one piece and inspect the pipe over its whole length for a hairline split — that split is the second most common cause of sand return and it is invisible with the pipe in place.
Pressure, channelling and when the sand itself is the problem
Not every Astral fault is a part. Two of the most common complaints are the media.
Rising pressure that a backwash does not clear means the sand bed has calcified or has been bound by oil and lotion into a crust. Sand does not wear out in the way people say, but it does clump, and a clumped bed channels: water finds a path through the crust instead of filtering. The pool goes cloudy while the gauge looks fine. Dig a hand into the top of the bed — loose grains that pour off your fingers are healthy, a bed you can pick up in a lump is finished. Replace the media and take the opportunity to inspect the laterals while you are in there.
Pressure that never rises is the opposite problem and is usually a cracked lateral letting water bypass the bed entirely. If the gauge reads the same at the end of a fortnight as it did after the last backwash, and the pool is not getting clearer, look at the internals rather than the pump.
Replace the pressure gauge while the tank is open. 4404020101 is the 1/8-inch back-mount gauge kit and 722R0100025 its O-ring; a gauge that has been sitting at the same reading for two seasons is usually seized, and every judgement above depends on it being honest.
Sand coming back to the pool: laterals and standpipes
Sand in the pool after a backwash is almost always a cracked lateral arm or a split standpipe, and the repair means emptying the tank. Do the identification before you start shovelling.
Laterals are sold by length, not by model. Pull one arm and measure it from the hub face to the tip. We stock three: 626 at 8-7/8 inches, 627 at 6-1/3 inches for the 19 and 22 filters, and 628 at 110 mm for the commercial tanks. Count the arms while the tank is open — replace the whole set, not the one that failed, because the others are the same age and the same brittleness.
Standpipes are sold by tank height. 22505-0017 is the 19-inch stand pipe and hub supplied without laterals, 22507-0017 the 22-inch, and 28300-0600 M the 26-inch. For the larger sand tanks, 157010201 covers the 20-inch and 24-inch filters.
Collector tubes and heads are the Millenium equivalent: 22502-0017 at 15 inches and 22503-0017 at 17 inches, with 05100R0400 covering the 20-inch, and the 8-arm collector head 15782R0202. On a Millenium the tee adapter 00555-0401 and the top-mount hose 09440r5003 are the two parts most often broken during a strip-down.
A note on brittleness: these internals are glass-filled polymer, and on a filter more than ten years old they snap when you look at them. If you are opening the tank for anything, plan to replace the laterals and the standpipe together. Going back in three months for the second one costs more than the parts did.
Lids, lock rings and the leak at the top
The top of an Astral filter is a closure, an O-ring and a clamp, and all three fail differently.
Lid O-rings first: 4404210302 is the filter lid O-ring across the widest range of tanks, 720R1750057 seals the valve body to the tank on Millennium filters, and 723R0049003, 721R1820060 (7.5-inch ID) and 722R0100025 (pressure gauge) cover the remaining seats. A lid that weeps only under pressure is an O-ring. A lid that weeps all the time is a cracked lid or a distorted ring.
Lock rings and clamps go by family. 18111R0006 is the general lid lock ring, 18224R0600 the lid and locking ring for the 50 and 100 filters, and 18225R0300 the same for the 2500 Series 75 and 150. The Millenium takes the clamp kit 24182R1003M; the 3000 Series takes lock ring 06671R0204 with reinforcing ring 06671R0205; 25296R0002 is the outside reinforcing ring. On Cantabric and Persius top-mount installations the valve is held by lock ring 4404180204, and 4411020402 is the plastic V-clamp set. Clear replacement lid 00555R0201A and the complete lid assembly 00497-5000 cover the tanks where the lid itself has crazed.
⚠️ A lock ring that will not tighten evenly is usually a distorted lid, not a worn ring. Fitting a new ring to a warped lid reproduces the leak.
Multiport valves: passing sand, passing water, or stuck
Three different faults, three different parts.
Water passing to waste while filtering is the spider gasket. 19028-0204 is the 1½-inch top-mount gasket, 19028R0203 the 1½-inch rotor supplied with its gasket, 07441R0002 the 2-inch rotor spider gasket for backwash valves, and 00600R0102 the general spider gasket. Replacing the rotor with the gasket is the better repair on a valve that has been leaking for a while — the rotor face wears into the gasket seat.
Sand to the pool through the valve points back at the standpipe, not the valve. Check the section above before buying valve parts.
A cloudy or broken sight glass takes 00600R0002 with gasket 00600R0001. Handle 00600R0201 and the lid label 22358R0201 22358R0202 cover the cosmetic failures that make a valve unusable in practice because nobody can read the positions.
Complete valves where the body itself has cracked: 22355 is the 1.5-inch for SM 3000, 22358 the top mount for the 100 Series, 2000 Millennium and 3000 Series, 9848 the 2-inch kit for the 30-inch 3000 Series sand filter, and 28226 the 2-inch side-mount backwash valve for 24-inch tanks. Valve lid O-rings are 7231400040 for the 22355 and 722R1362035 for the general valve lid.
Drains, air relief and the small parts that end a service call
These are the parts that are never on the truck and always needed.
Drain caps and plugs: 18111R0010 water drain cap, 15780R0602 water drain plug, 24181-0004 the 3/8-inch water drain set, 0599060 the 3/8-inch drain cap, 00541R0400 the water drain kit, and 4404220103 the drain plug kit specific to Millenium side-mount filters. Gasket 24181-0006 goes with them; 00470R0319 is the plug O-ring.
Air relief and gauges: 4404210304 air relief plug, 4404020101 the 1/8-inch back-mount pressure gauge kit, and 00648R0202 the air relief gasket on Cantabric tanks. A filter that will not purge air after a backwash usually has a blocked relief plug, not a pump problem.
Plumbing connections: bulkhead flange 00470R0211 in 1½ inch, union nut 00611-0002, union connection 15623-0302 in 2 x 1½ inch, and union adapter 27455-0206. Housing and lid O-rings for the 1600 Series are 7731520035 and 7731329035, with union adapter O-ring 7730599035.
Skimmer parts that share the range: standard skimmer basket 4402010103, round deck lid 00249R0007, and the back ring 19028R0205, security clip 19028R0206 and drain plug 19028-0103 that go with the smaller assemblies.
Sprint pumps
Where an Astral pump came with the filter, the wet end parts are stocked alongside: impellers 23374-0002 (1 HP), 23375-0002 (1.5 HP) and 23376-0002 (2 HP), diffuser 05091-0003, strainer basket 01150-0202, locking ring 00648-0001 and motor clamp O-ring 7731838026. Impeller selection is by horsepower, and on a pump whose motor has been swapped the plate on the motor is the authority, not the one on the pump body.
What to send us when the badge is gone
Most Astral enquiries arrive as a photograph of a tank with no label, which is fine — the following four things identify it:
- Tank diameter at the widest point, and whether the tank is fibreglass laminate or moulded polymer.
- Valve position — on top of the tank, or on the side.
- Lateral length from hub face to tip, and the arm count, if the tank is open.
- Standpipe height from the tank floor to the hub.
With those four we can place almost any Astral sand filter and quote the internals against it. If the tank is still closed, the diameter and the valve position are usually enough to narrow it to two candidates, and the lid ring settles it.
Sourcing
Astral is the fifth-largest brand in our catalogue and among the least well served by general distributors, because the range fragments by tank size in a way that makes it awkward to stock. We carry the internals — laterals, standpipes, collector tubes and heads — alongside the lids, lock rings, valve parts, O-rings and drain hardware, with full model coverage on the Astral brand page.
For service companies running fleets of these filters, the parts worth holding are the laterals in all three lengths, the lid O-ring 4404210302, and one spider gasket per valve type. Those three lines cover most of what actually stops a filter.
