Sand in pool after backwashing Triton filter

[pumpkineater59]

We remodeled the pool 8 months ago. At that time, we added a Triton II TR140 sand filter. It has gravel in the bottom with sand of top. I've only had to backwash the filter twice. The first time was fine but after the second backwash, I found gravel and sand in the pool, more gravel than sand.

I back washed for a total of about 5 minutes. During this time, the flow at the P-trap slowed down after about 3-4 minutes. It didn't pick up again. I rinsed for about a minutes and then back to filter mode. When starting in filter mode, I could hear crackling in the pipe (gravel).

As I haven't seen this prior to the back wash, and it stopped dumping gravel and sand in the pool after the first day, what should I expect? Is this s one time occurrence, are the laterals cracked, or could the back wash flow be too high? I did back wash on the highest speed (3410 RPM) using a Pentair VS pump.

I appreciate any help you may have.

/Peter

 

[jblizzle]

Sounds like the filter must have broken lateral or something that allowed the gravel to get to the pool ... Likely clogged up with gravel if the flow is reduced.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[pumpkineater59]

Thanks jblizzle.

I should have mentioned that after but back in filter mode, the flow rate is back top normal.

If I have a broken lateral, wouldn't I see gravel coming through all the time or only after back washing? My thinking is as the lateral is at the bottom outlet, the gravel would push through continuously?

 

[jblizzle]

The gravel can only get to the pool on filter mode because it is below the sand. Guessing that it stops when the hole/crack gets jammed. When backwashing, the jam gets broken up and then when switching back to filter, the gravel gets to the pool until the hole is jammed again.

I am not sure though why you would lose flow on backwash but good flow on filter though, unless I have that backward to what you see.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[duraleigh]

or could the back wash flow be too high? I did back wash on the highest speed (3410 RPM) using a Pentair VS pump.

Well, I don't know if that issue has been reported on the forum but I wonder if that big, strong pump was powerful enough to completely disrupt the sand and gravel bed and blow some gravel in the multi-port which then entered the pool when you switched back to "filter". It sounds feasible but I don't know that we've ever had the issue.

 

[PJ]

Did you install the filter yourself? Since it was only a one time occurrence this is my theory. When whoever put sand/gravel in the filter, they failed to cover the standpipe with something to block the material from getting in there. A little bit of sand and gravel found its way into the pipe, and it made its way out after a couple of backwash cycles.

 

[RobbieH]

When mine was broken (never identified where) I only got sand in the pool at initial pump start-up. I always let my sand settle for 30 seconds or more after backwashing, before going back to filter. are you doing the same?

 

[JasonLion]

I can imagine some sand getting into the pool. That should never happen, but it is still plausible. However, I can't really image gravel getting out of the filter and into the pool.

A broken lateral would not be sufficient, as the joint between the lateral and the riser pipe should not be large enough to let gravel through even if the lateral was completely removed. Also, a broken lateral would allow sand through any time the pump was in filter mode, and from your description that does not appear to be happening. That also appears to rule out some of the more dramatic ways the filter could be broken, since any of them would release sand in filter mode as well as backwash mode.

PJ's theory about sand/gravel in the standpipe could easily result in sand/gravel coming out the backwash hose, but it is far more difficult for that to account for sand/gravel getting into the pool.

 

[pumpkineater59]

Thank you all.
it's now been a couple of days since the backwash and I do not have any more gravel/sand in the pool, though I haven't tried to backwash again. What is interesting is that the gravel/sand only exited into the pool via the closest outlet to the equipment, which is on a baja reef. The other baja reef outlet did not get any. Of course there might be some at the deep end but until I vacuum (weekend job) I don't know for sure. There is nothing that i can see.

I went to the pool store to see how long it would take to get new laterals, and the salesman suggested that the gasket in the multi-port valve might be broken/ripped. If so, gravel/sand may leak to the pool.

The pool builder installed the filter, though I purchased it (craigslist deal). I wasn't there when he filled the gravel and sand.

I don't think I waited that long, 30s, between the backwash, rinse, and filter modes.

What is the standpipe? How do I identify where it is? Is it the pipe the goes from the top inlet/outlet and have the diffuser ontop?

 

[JasonLion]

I went to the pool store to see how long it would take to get new laterals, and the salesman suggested that the gasket in the multi-port valve might be broken/ripped. If so, gravel/sand may leak to the pool.

That is certainly a way that sand could get into the pool, but gravel would not be able to get through the relatively narrow slots that open up when the gasket is damaged.

 

[Bama Rambler]

Personally I would backwash it again, maybe a couple of times and see if it keeps doing it. If it does then tear into the filter and see what's going on. If it was the gasket in the multiport I doubt that it would let gravel through. If it was a broken off lateral it would let sand through all the time. I think since you haven't backwashed it but a couple of times it's left over gravel/sand from the initial fill.