Hayward S310S Sand Filter Lateral Replacement: How to Upgrade Discontinued SX242MA2 & SX310CD2FW Parts
Replacing the internal lateral assembly in an older Hayward S310S sand filter can be confusing when the original parts are discontinued. This guide explains the current replacement path, why the lower elbow must be replaced with the lateral assembly, and when a dry-fit standpipe adjustment may be needed.
If your Hayward ProSeries S310S sand filter has a cracked lower elbow, damaged folding lateral holder, or sand returning to the pool, you may discover that the original replacement part numbers are no longer available.
The common older S310S internal parts are SX242MA2, the folding lateral holder assembly, and SX310CD2FW, the lower elbow assembly. Both are legacy configurations. The current repair route is an updated matched internal assembly, but it is important to understand that this is not always a simple “swap one part and go” repair on every older tank.
What Is the Problem With Older Hayward S310S Internal Assemblies?
The S310S is Hayward’s 30-inch ProSeries side-mount sand filter. Older versions commonly use a folding umbrella-style lateral assembly at the bottom of the tank, connected to a vertical standpipe and lower elbow.
Over time, the lower elbow can crack, the lateral holder can wear or break, or the laterals themselves can become damaged. When this happens, sand may bypass the filter internals and return to the pool through the return lines.
Important: Do Not Replace Only One Half of the Updated System
The old lateral assembly and old lower elbow were designed to work together. When converting to the newer replacement design, the updated lateral holder and updated lower elbow must be used as a matched set. Reusing the original elbow with a newer lateral holder can create alignment and fitment problems.
Original Discontinued Parts vs. Current Replacement Path
| Older Part Number | Original Function | Current Repair Direction |
|---|---|---|
| SX242MA2 | Folding lateral holder assembly for S310S | Updated lateral assembly configuration |
| SX310CD2FW | Lower elbow assembly for S310S | Updated matching lower elbow configuration |
| SX310MA2S | Not the original older configuration | Current complete matched lower assembly route, including lateral holder, vertical pipe, and lower elbow |
The most practical replacement option is typically the complete SX310MA2S lower assembly. This approach avoids mixing an updated lateral holder with an older elbow or trying to piece together internal components that may not share the same geometry.
What the Complete Assembly Solves
A complete matched assembly provides the folding laterals, the vertical center pipe, and the updated lower elbow together. That matters because the bottom connection and standpipe height must work together.
Why Prior “Direct Fit” Attempts Fail
On older filters, replacement parts can appear nearly identical but sit at a different height or use a revised elbow connection. That can prevent the upper diffuser and valve connection from seating correctly.
Does the SX310MA2S Require Modification?
The honest answer is: possibly, but not always.
The SX310MA2S is the proper updated complete replacement path for the discontinued internal components. However, some older S310S tanks may require a field-fit adjustment because the new vertical standpipe can sit slightly too tall once the updated lower assembly is fully seated at the bottom of the tank.
This does not mean the tank, lateral arms, or elbow should be cut. The only possible modification is a small trim to the vertical center standpipe, and only after the new assembly has been dry-fitted correctly.
Aqua Terra Backyard Repair Tip
Never measure the old standpipe and blindly cut the new one to the same length. The updated lower elbow changes the relationship between the tank floor, lateral holder, and standpipe. Always install the updated lower assembly first, then dry-fit the upper diffuser connection before making any cut.
How to Dry-Fit the Updated SX310MA2S Assembly
Before adding sand or making any modification, use this dry-fit process to confirm whether the new standpipe needs to be shortened.
-
Remove the old internal assembly completely.
Remove the damaged folding lateral holder, old standpipe, and old lower elbow from the empty filter tank. -
Install the updated SX310MA2S as a complete assembly.
Use the new lower elbow included with the assembly. Do not reuse the original elbow. -
Open the folding laterals.
Make sure all lateral arms are fully unfolded and resting naturally on the tank floor. -
Confirm the lower assembly is seated flat.
The lateral holder and lower elbow must sit naturally in their intended position without lifting, rocking, or forcing the assembly. -
Dry-fit the top diffuser and upper connection.
Install the upper internal components without sand and verify that they line up naturally with the new center standpipe. -
Check standpipe height.
If the upper diffuser or connection cannot seat fully because the standpipe is too tall, mark the standpipe at the correct height only after confirming the lower assembly is fully seated. -
Trim only the vertical standpipe if necessary.
Remove the assembly, make a square cut, remove all burrs, and clean away every piece of plastic debris. -
Reinstall and dry-fit again before adding sand.
Confirm the top connection fits naturally, the lower assembly stays seated, and no components are under stress.
Do Not Cut These Components
Do not cut the filter tank, folding lateral arms, lower elbow, diffuser, or valve connection. The possible adjustment applies only to the vertical center standpipe, and only if dry-fitting confirms it is preventing correct upper alignment.
How Do You Know the Standpipe Is Too Tall?
A standpipe adjustment may be needed only when all of the following are true:
- The updated lateral assembly is fully seated flat on the tank floor.
- The new lower elbow is installed as part of the complete assembly.
- The folding laterals are fully opened and positioned correctly.
- The upper diffuser or top connection will not seat naturally.
- The standpipe is the part physically preventing the upper assembly from fitting.
If the upper connection fits naturally with the complete new lower assembly installed, no trimming is needed.
Why the New Lower Elbow Must Be Installed
The updated lower elbow is not optional. It is part of the revised internal assembly geometry. The lateral holder, vertical pipe, and lower elbow determine where the assembly sits inside the tank and how the standpipe aligns with the upper diffuser.
Trying to use the new folding lateral assembly with the old lower elbow can change the standpipe height, prevent proper seating, or create a mismatch that leads to another failed repair.
When Should You Call a Pool Professional?
A capable DIY pool owner may be comfortable completing this repair, especially if they have previously serviced a sand filter. However, hire a qualified pool professional when:
- You are unsure whether the issue is the lateral assembly, standpipe, diffuser, or valve connection.
- The tank has cracks, damaged threads, or signs of structural stress.
- The upper connection will not seat after a proper dry-fit.
- You are not comfortable cutting PVC squarely and deburring it properly.
- The filter has been returning sand and you need help determining whether other internals were damaged.
Hayward S310S Lateral Replacement FAQ
What replaces the discontinued Hayward SX242MA2 lateral assembly?
The current replacement route uses the updated S310S lateral assembly configuration. Because the updated lateral holder and lower elbow are designed to work together, the complete SX310MA2S assembly is often the cleanest repair path.
What replaces the Hayward SX310CD2FW lower elbow?
The old lower elbow should be replaced with the updated matching elbow used with the new lateral assembly. The SX310MA2S complete assembly includes the matched lower components together.
Will SX310MA2S fit every older S310S filter without modification?
Not necessarily. It is the correct updated repair path, but older tank revisions can require a dry-fit check. A minor standpipe trim may be necessary if the upper connection cannot seat naturally after the new lower assembly is fully installed.
How much should I cut from the new standpipe?
There is no universal measurement. The correct amount depends on how the new assembly sits in your individual tank. Dry-fit first, mark only after the lower assembly is fully seated, then trim only enough for the upper diffuser and connection to fit naturally.
Can I reuse my old lower elbow with the updated lateral holder?
No. The updated lower elbow should be installed with the updated lateral assembly. Mixing older and newer internal components is a common reason for fitment problems.
Need Help Confirming Your Hayward S310S Repair?
Before ordering replacement internals, send Aqua Terra Backyard clear photos of your existing lateral assembly, lower elbow, standpipe, diffuser connection, and filter model label. We can help identify the best available replacement path and help you avoid ordering parts that do not match your filter’s internal configuration.