While vacuuming the pool, the dirty water shoots back into the return. we replaced the sand, and laterals looked in tact.whay is it doing this?

If you took "Pump" apart, you wouldn't have found broken laterals. You will need to open up the "Filter" to find laterals. If sand is ending up in the pool, you either have a broken component within the filter or you have an overfilled filter tank and during backwash sand is lifted up into the valve, and upon returning valve position back to "Filter" the residual is blown back to pool via the return inlet. If this is the case that is why always follow label / owners manual directions as to Quantity of media to add. More is not necessarily always better!

Cloudy water is the bane of sand filters!. I suggest letting filter run day and night. Do not backwash until the pressure rises 8 - 10 pounds above clean starting pressure. Do not try to vacuum or stir up the sediment. when water clears, vacuum to waste. Keep the hose running while vacuuming. A dirty filter is a better filter (up to a point). At a higher pressure the filter will trap more of the fine particles that are clouding your water.

sand filters only have limited filtration. If the dirt is very fine such as dead algae, it will go right through the filter. Use a clarifier to help give the filter finer filtration. Do not vacuum until you can see what you are doing, then vacuum on 'waste'

Sand can be sent to the pool for several reasons. If it is piped in reverse, if the laterals, their manifold, pipes connected to the manifold is damaged or there is a problem in the backwash valve. The water from the filter enters the filter above the sand where it soaks through the sand, through the laterals and out the return pipe to the filter. If the water is flowing from the pool into the laterals and through the sand and into the pool some sand will go with the water into the pool. In addition, the laterals will get filled with dirt from the pool. The best way to know if there is a damaged lateral, manifold or pipe is to remove most of the sand and inspect these parts. After the filter is worked on, If some sand was in the laterals, manifold or pipes when a system is started it should be sent into the pool and find can then be brushed into the main drain and be caught in the filter. I hope this helps.

The lateral assembly in the bottom of the sand bad inside the filter is broken. You may not even see damage on it when replacing it but it is the problem. Replace the sand while you are at it. Be sure to fill the tank half-way with water before adding sand back into the filter. Also be sure to cap the top of the lateral assembly so sand doesn't get into the standpipe that inserts into the bottom of the valve.

John

This is a serious issue. These vessels are only pressure rated to 50 PSI. Anything more can be an explosion hazard.SHUT DOWN THIS SYSTEM!

You need to remove all the sand and replace it. While your inside, you must clean the LATERALs. (small tubes on bottom of the filter)

This will reduce the pressure.

It is a good idea to replace the laterals in the bottom of this filter if it is in your budget to do so. The pvc laterals become brittle and often break when tampered with .

Note: only use #20 silica pool filter sand as a replacement.

Try changing the setting on your pool filters control valve to waste. This will bypass the filter and vacuum directly to waste. If this works, it could be a problem with the filter's "filter" setting and you may need to service or replace your control valve.

You have a problem ...

Can you see the little tube that bleeds air out of the return pipe? If not ... see if you can find it and get it to the top of the filter.

Still have sand? You may have a cracked lateral ... remove the sand and check all the laterals. Replace any that are broken.

When you refill the sand ... be sure to put water in first to soften the beating the laterals take from the falling sand.

It could be any of the following.
1. If you recently added sand into the filter Sand might have been poured in to the standpipe when being added to the tank.
2. A broken or worn out lateral . (One of the slotted tubes) on the bottom of the tank that water passes through on it way back to the pool. A lateral acts as a strainer keeping the sand in, lets the water out.
3.. A cracked standpipe the tube that sits in the tank, connects into the filter head
4. Filter head O-ring maybe dislodged. It's located where stand pipe connects, to the filter head inside the head.
5.. The hoses on the filter maybe hooked up backwards. The hose going from filter to pump may be connected from filter to pool.

SOUNDS LIKE YOU ARE IN RECIRCULATE MODE TAKE HANDLE AND MOVE IT TO ALL THE POSITION TO TEST BACK WASH CYCLE ETC SAND SOULD BE FINE CHECK TO SEE IF YOU HAVE ENOUGH