Frequently Asked Questions
Here at swimmingpoolsupplies.co.uk we pride ourselves on the unbiased advice that we offer, here are some of the frequently asked questions we receive, if there is a question we haven't answered here either call us on 01924 479717 or send us an email from our Contact Us page.
Filtration Problems
How often should the sand in the sand filter be changed and if so, can I do this myself?
We would recommend changing the sand about every 3 years. The sand starts to cake from the outside of the tank inwards reducing the effective filter area. It is possible to change the sand yourself.
You need to check with the filter manufacturer’s instructions on the recommended media and method for your filter. These instructions should also advise how much sand your filter holds. If you don’t have the instructions, we will be able to advise if you let us know the make and size of your filter. Most filters are sand based though some sand filters are filled with Zeolite which is a micro-porous volcanic material acting as a finer filter than sand.
Changing the sand is quite straightforward but a little laborious. You will need to make sure you can get a new 'O' ring seal just in case the old one doesn't reseal properly. The process is quite simple, remove the lid, (a tool can be obtained for this), remove any top pipe work, dig out by hand or vacuum out all the old sand and replace with the new sand.
The following are some useful tips;-
- Be sure not to disturb the thin black tube sticking through to the top of the filter. This is an
air bleed tube and is the only way out for air trapped in the top of the filter tank.
- Be careful when removing the sand from the bottom of the filter to avoid damaging the laterals. These are thin tubes with slits which allow the passage of water but not sand. If they are damaged the sand will be pumped through the system into the pool.
- When refilling the filter put some water in first. This stops the sand settling in piles on
top of the laterals and damaging them.
- Use plastic bags to protect the filter top threads from getting sand in them. Put a plastic bag,
with the base opened, over the threads and another over the top pipe to prevent
sand entering the pipe work to the multiport valve.
- If the filter has a multiport valve which screws straight into the top of the tank you'll need a special tool which protects the thread and the pipe, and holds the pipe central to the tank.
This is necessary to allow the valve to screw down.
- Last but not least, backwash all the dust out of the sand before setting the multi-port valve back to filter.
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My sand filter seems to be pumping filter sand into the swimming pool. I have checked the laterals for cracks and they seem to be in good condition. Could there be any other way for sand to bleed into system? If I have too much sand could that cause the problem?
Sand in the swimming pool is usually the result of broken or misshapen laterals or the air bleed tube being out of place. The sand in these cases drops out of the return jets and forms a pile below. When refilling the filter with sand, part fill it with water to prevent the sand settling on a lateral and bending or breaking it.
There are a couple of other problems which could be mistaken for sand in your pool, these are magnesium salts and dead algae, which looks like sand and will, when brushed, disappear into the water, only to settle later in a similar position. Even if you vacuum these sediments they will pass through the filter, through the sand and again re-appear in similar locations as before. The solution is to vacuum it to waste (vacuum with the multiport valve set to the waste position, the vacuumed water then goes straight out of the waste pipe and not through the filter). You will lose around 6" (15cm) of water.
My sand filter is running at 2 bar. Last summer it was 1.5. I have backwashed many times over the last couple of days. What should I do?
Set the multiport valve to re-circulate and re-check the pressure with the filter out of the formula. If the pressure is still high then you may have a blockage somewhere else in the system. It may be in the heat exchanger in the gas heater or the bypass in the header has jammed or the non-return valve at the base of the heat-sink is jamming part closed. If the pressure drops to the normal or lower when on that position it suggests that the sand is "caked" and needs changing, or at least the filter lid taken off and the sand given a good stir (careful not to damage the laterals whilst doing this).
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My sand filter is running at 2 bar. Last summer it was 1.5. I have backwashed many times over the last couple of days. What should I do?
Set the multiport valve to re-circulate and re-check the pressure with the filter out of the formula. If the pressure is still high then you may have a blockage somewhere else in the system. It may be in the heat exchanger in the gas heater or the bypass in the header has jammed or the non-return valve at the base of the heat-sink is jamming part closed. If the pressure drops to the normal or lower when on that position it suggests that the sand is "caked" and needs changing, or at least the filter lid taken off and the sand given a good stir (careful not to damage the laterals whilst doing this).
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How often should I backwash my filter?
You need to backwash your sand filter about once a week. Sand filters become more efficient the more debris the sand has trapped. The particles that are trapped effectively become part of the filtering medium, enabling the sand to trap smaller particles.
Most manufacturers recommend backwashing when the filter gauge reading increases to 8 to 10 pounds per square inch (psi) above the clean starting pressure (some recommend backwashing after a 6 to 8 psi increase). Following the recommendations of the filter manufacturer will ensure long, efficient filtering cycles and will save on water, chemicals and energy costs.
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