Pool return shooting out sand?

[Chomdo]

My pool was constructed about 7 months ago and now I have a new problem. My return is shooting out sand. After I took the eyeball out last week, I thought I would really clear the pipes and vacuum after I see that nothing is coming out anymore. For a few days now it seemed like the amount of sand under the return (on the pool floor) was not increasing. So today I thought I should vacuum the pool and as soon as I had finished and cleaned the pump basket and turned on the pump again, the return shot out a handful of sand again. What could be causing this to happen all the time? Also, what I don't get is that why does it happen after I've stopped vacuuming and cleaned the pump basket. I mean while I was vacuuming no sand was coming into the pool, so how come right after I finish and turn the pump on again?

 

[needsajet]

Hi Chomdo, does this look like your filter... Emaux V650 sand filter | Free Freight | Monarch Ecopure F25 | Zodiac Titan Z650 sand filters | Brisbane | Gold Coast | Sunshine coast.
If so, it's the same as my Zodiac. Is it filter sand you're seeing in the pool? It's sounding like a displaced, unseated or broken lateral.

At the bottom of the filter are several "laterals" which are small pipes arranged like the spokes of a wheel. These have slots in them too small for the sand, so the sand stays in the filter, and only water comes back to the pool. If a lateral is not installed correctly into the receiver, or if a lateral is cracked or broken, some sand can get past and into the return pipes. This thread includes a full tutorial on how a sand filter works: Deep Cleaning a Sand Filter

It's also possible that the sand got into the riser pipe during construction. That sand should have been flushed out the backwash during rinsing, but if it wasn't rinsed, or not rinsed enough, some sand might have gotten into the return pipes and some could be sitting in the bottom of the pipes running back to the pool, but you'd expect that to be gone by now.

To check the laterals, you'll need to disconnect and drain the sand filter, remove the sand (save it in a wheelbarrow because you can re-use it), and then you can inspect/repair the laterals. A wet/dry shop vac can be used to suck the sand out. Our pool builder said it's not uncommon for the people in the factory not to seat the laterals fully, and we checked all of mine before adding the sand.

The reason the sand comes out after restarting the pump after vacuuming is because the flow rate is higher without the vacuum attached, so more flow and more chance to move any sand that's laying in the pipe, or more force inside the filter pushing sand through a cracked lateral or poorly connected lateral. You mentioned removing an eyeball, which would have allowed more flow as well.

 

[msdunkel]

I had this problem a couple months ago. I had a bad stand pipe inside the sand filter which was allowing sand into the pool. The unfortunate side effect of this was it clogged my pool's auto vacuum and destroyed the pump. If you've got a lot of sand going into the pool you need to fix the filter quickly and you might need to turn off your automatic vacuum in the meantime. Expensive lesson learned.

 

[Chomdo]

Hi Chomdo, does this look like your filter... Emaux V650 sand filter | Free Freight | Monarch Ecopure F25 | Zodiac Titan Z650 sand filters | Brisbane | Gold Coast | Sunshine coast.
If so, it's the same as my Zodiac. Is it filter sand you're seeing in the pool? It's sounding like a displaced, unseated or broken lateral.

At the bottom of the filter are several "laterals" which are small pipes arranged like the spokes of a wheel. These have slots in them too small for the sand, so the sand stays in the filter, and only water comes back to the pool. If a lateral is not installed correctly into the receiver, or if a lateral is cracked or broken, some sand can get past and into the return pipes. This thread includes a full tutorial on how a sand filter works: Deep Cleaning a Sand Filter

It's also possible that the sand got into the riser pipe during construction. That sand should have been flushed out the backwash during rinsing, but if it wasn't rinsed, or not rinsed enough, some sand might have gotten into the return pipes and some could be sitting in the bottom of the pipes running back to the pool, but you'd expect that to be gone by now.

To check the laterals, you'll need to disconnect and drain the sand filter, remove the sand (save it in a wheelbarrow because you can re-use it), and then you can inspect/repair the laterals. A wet/dry shop vac can be used to suck the sand out. Our pool builder said it's not uncommon for the people in the factory not to seat the laterals fully, and we checked all of mine before adding the sand.

The reason the sand comes out after restarting the pump after vacuuming is because the flow rate is higher without the vacuum attached, so more flow and more chance to move any sand that's laying in the pipe, or more force inside the filter pushing sand through a cracked lateral or poorly connected lateral. You mentioned removing an eyeball, which would have allowed more flow as well.

Thanks a lot for your answer. I guess the problem could also be with the lateral in the filter. I don't recall the return shooting out sand before now but several times it did shoot out pieces of concrete that must be from the careless construction guys. Actually the reason that I took off the eyeball last week was because I had a very large peace of concrete stuck in the return and blocking the water flow. I was really surprised to have a concrete chunk like that coming out 7 months after construction. I don't really get it how it's even possible that it wasn't flushed out before. Other pool owners in Thailand have reported concrete coming out long after the pool was constructed.

Anyway the sand kind of started coming out after I had taken the eyeball off and flushed that big piece of concrete, so I don't know how this would be related to the filter? Does it make any sense or could this just be some left over sand from construction still stuck in the pipe walls? What I've observed now is that maybe max one teaspoon of sand comes out of the return right after vacuuming (as soon as I turn on the pump on filter mode again), but I don't see that it would continue coming out. For example now I didn't vacuum for a week because I wanted to see how much sand would come out. Yesterday before I vacuumed it looked like the amount of sand was the same as a week ago, so it seems that the return just shoots out a bit of sand after vacuuming but not continuously.

I'm not exactly sure what the sand in my filter would look like compared to the sand used in concrete mixture. I guess the grains are slightly bigger than beach sand and varied in colour (brown, black, white..) I just hope the problem is not in the filter, because I haven't really had a trouble free period with my pool since it was constructed.

Below is a picture of my filter.

- - - Updated - - -

My Emaux sand filter

 

[Chomdo]

Thanks for the reply! When the filter was letting sand into the pool from the return, was it doing it constantly or just after vacuuming only? I only get about one teaspoon of sand on the pool floor within the first 10 minutes after I switch the pump back on after vacuuming and then it seems to stop. The problem isn't that big because the amount of sand is not much but it just feels worthless to vacuum when that handful of sand always comes out right after I've cleaned the pool floor. I just really want to make sure where it's coming from and how to stop it.

 

[needsajet]

K, if you had a chunk of concrete in there, it would have acted as a bit of a dam and probably had sand behind it, hopefully just from construction as you suggested. Glad to hear that's out of there! They probably didn't tape or cap the pipe ends when they shot the gunite. If it's out, all good!

I would just keep running/vacuuming as I saw fit. You can use a skimmer sock, or hairnet, or nylon knee high, in the skimmer basket, which will catch larger stuff. Even just the skimmer basket by itself, and the pump basket, have holes small enough to protect the pump.

I flushed my lines before plaster, after I finished the pipe from pool to filter pad but without any equipment in yet, just using a garden hose. A fair bit of stuff came out, but the pool builder thought I was nuts and had never seen that done, so what you're experiencing may not be all that unusual

 

[Chomdo]

Yes I hope so too. I've had the pump running maybe for about 10 days (some 4-8 hours a day) since the concrete chunk came out so it is a bit weird that sand would still come out, but I hope it's just that and not the filter.

From what I explained, does it sound like it wouldn't be the lateral in the filter? If the filter was letting sand trough wouldn't it kind of come out all the time when the pump is running or could it also behave like this that it only shoots out some sand when the pump is turned on after vacuuming.

When I vacuum with the skimmer I don't have the skimmer basket there of course but the pump basket does catch even quite small pieces. Last time some of the sand was under the pump basket and I just opened the pump drain to wash it out.

 

[needsajet]

It's very hard to say. There are several laterals in the filter by the way. Mine has 8 if I remember right.

Filter sand would not get caught in a pump strainer basket. It's small enough to go right through the basket and pump and get caught in the filter. Here's a picture:
Filter Sand | Clark Rubber You can see that it's graded so that the bits are neither too big or too small.

I'm wondering if they just used some sort of cheap sand. If there are fines in it, that could be getting pumped through I suppose. Hopefully someone else who has seen this chimes in.