sand filter outlet pipe from lateral hub

[pthreadunixman]

I just bought a house and inherited a troublesome STA-RITE cristal-flo (side mount) sand filter. After the initial problem of sand blowing out returns and blocking the return lines, I suspected a broken lateral; however, upon opening the filter, I found the sand bed had funneled down to where the inlet pipe enters the lateral assembly hub where they had blown apart. Obviously, this was allowing sand to escape in mass.

After digging out all the sand and removing the lateral assembly, I tested the fit of pipe and hub. The hub fits very loosely over the end of the pipe. In fact, it fits so loosely that it will fall off the end of the pipe if not supported from underneath. Is this right? I can't imagine that such a fit would stay together under pressure during a backwash. Is it supposed to be just friction fit or should there be a threaded fitting there?

To make it clear, the outlet pipe I'm talking about is a piece of grey flex pipe that goes into a PVC elbow and is connected to a short length of rigid PVC. It's this rigid piece that joins to the lateral hub.

 

[Bama Rambler]

I don't have any experience with those filters but that certainlyh doesn't sound right. Maybe someone with more experience will be along to help you out.

 

[pthreadunixman]

I've attached a diagram/photo that's pretty close to what I have. I've circled in red the problem joint.

[attachment=0:b89wpg1m]a_hrv_hi-sand_filter.png[/attachment:b89wpg1m]

 

[duraleigh]

pthread,

I don't have that filter either but that is a standard connection for a side mount. Like you, I cannopt see how the pipe would even stay connected during a backwash. That said, it's hard to imagine they could "accidentally" forget to make a solid connection. Are you able to get in touch with tech support or finda a parts diagram online?

 

[pthreadunixman]

Found a parts diagram.

[attachment=0:3cei7qo5]filter-parts-diagram.jpg[/attachment:3cei7qo5]

It looks like a slip connection there as well. I guess I'm going to have to resort to modding this thing so it stays together.

Does PVC solvent typically work on the hard plastic the hub is made out of? I'm thinking of inserting a 2" -> 1.5" bushing (slip-threaded) into the hub and the same on the elbow. Then join hub to the elbow with a short threaded nipple. Would the constriction of the pipe at that point be a concern?

 

[duraleigh]

If it's a slip connection on the diagram, I wouldn't change it until I talked with an expert. Pentair has a good tech support system and I would call them if you can't get anyone else. Perhaps the weight and mass of the sand hold the grey pipe in place and it is supposed to not be tight to allow for some movement if the sand shifts. I'm just stabbing in the dark but I would be reluctant to alter it without first knowing what the intent was.

 

[pthreadunixman]

For completeness sake, here's what I wound up doing.

I cut a 5mm wide slot (with a Dremel style tool) in the collar of the hub fitting to give it some flex and clamped it down to the pipe with a SS hose clamp. It now survives repeated backwashings without blowing apart and spewing sand into the pool.

 

[duraleigh]

Clever fix! I wonder why they made it like that in the first place?

 

[BriceJohnson]

Generally those connections are glued. Its possible that the glue joint just broke over time (although if it failed like it sounds like it did, it was a crappy glue joint). There's a reason we killed the side mount cristal flo though, it wasn't the greatest filter.

You can glue the two pieces together if you'd like. I'd use MEK instead of standard PVC glue, the hubs are generally ABS plastic. MEK will disolve both the PVC and the ABs to get a good bond.