Sandfilter Backwashing

[tamsin]

My gardener attempted to backwash the sandfilter and the water dropped like a stone, about a foot, just past filter outlet box on a side of the pool. After topping the pool up, the same thing happened when the automatic start to the pump kicked in. What's he done? Sand filter has filter-rinse-whirlpool-backwash-closed and drain printed on the top where the handle is. Lost the manual, no name printed on the filter, and seller's instructions clear as mud.

[cdnvic]

Sounds like there may be some air in the system and the water level dropped as that was being displaced. Top up your pool again and keep an eye on it for a while. If the pump is making variations in pitch then it's probably air working out of the system.

How big is this pool? (litres)

[Naam]

My gardener attempted to backwash the sandfilter and the water dropped like a stone, about a foot, just past filter outlet box on a side of the pool. After topping the pool up, the same thing happened when the automatic start to the pump kicked in. What's he done? Sand filter has filter-rinse-whirlpool-backwash-closed and drain printed on the top where the handle is. Lost the manual, no name printed on the filter, and seller's instructions clear as mud.

the multiport valve might be still on "backwash" (perhaps even on "drain") and not on "filter".

[Naam]

Sounds like there may be some air in the system and the water level dropped as that was being displaced. Top up your pool again and keep an eye on it for a while. If the pump is making variations in pitch then it's probably air working out of the system.

no way.

[cdnvic]

Sounds like there may be some air in the system and the water level dropped as that was being displaced. Top up your pool again and keep an eye on it for a while. If the pump is making variations in pitch then it's probably air working out of the system.

no way.

Depending on the size of the pool this could easily explain an initial drop in level. All depends on the displacement of the pool, and the distance to the pump. If the valve were still on drain it would continue to fall, not just momentarily drop.

[Jai Dee]

Don't worry about the setting of the multiport valve for now... it sounds to me like the ball valve on the outlet side of the multiport valve is open... thus dumping the water straight to waste.

The multiport valve should be set to the filter setting, and the handle on the ball valve on the outlet should be in the closed position, ie. at 90 deg to the pipe run direction.

Your gardener probably forgot to close the valve after backwashing (and hopefully rinsing).

[Naam]

Sounds like there may be some air in the system and the water level dropped as that was being displaced. Top up your pool again and keep an eye on it for a while. If the pump is making variations in pitch then it's probably air working out of the system.

no way.

Depending on the size of the pool this could easily explain an initial drop in level. All depends on the displacement of the pool, and the distance to the pump. If the valve were still on drain it would continue to fall, not just momentarily drop.

the OP should define "the water dropped like a stone, about a foot" and state the size of his pool. does "dropping like a stone" mean one second or ten minutes? "a foot" means nothing if the "pool's" size is 2x3 meters.

by the way, one interesting fact: multiport valves should be turned only in one direction or the seal will get damaged sooner or later.

[tamsin]

The pool is sixty square metres, how many litres this is I cannot say, Archemedes I am not. But I think the theory as to the handle not being set back in its rightful position 'filter' is probably the correct one. It was like emptying a bath. Anyway. I shall reset the handle and order yet another cart load of water. Can someone please verify the correct backwashing procedure please? I'll do it myself in future. I'm supposing it's pulling the handle around the front, anti-clockwise, from 'filter' past 'rinse' and 'whirlpool' and then setting it on 'backwash' for a minute or so? And then returning where? Back around the front again (clockwise)? Or proceeding anti-clockwise to 'closed', 'drain' and back to 'filter? You're right. Don't want to wreck the mechanism by forcing it in the wrong direction. Bit expensive. Thankyou all for your help.

[Jai Dee]

There's some detailed instructions on this website.

[Naam]

The pool is sixty square metres, how many litres this is I cannot say, Archemedes I am not. But I think the theory as to the handle not being set back in its rightful position 'filter' is probably the correct one. It was like emptying a bath. Anyway. I shall reset the handle and order yet another cart load of water. Can someone please verify the correct backwashing procedure please? I'll do it myself in future. I'm supposing it's pulling the handle around the front, anti-clockwise, from 'filter' past 'rinse' and 'whirlpool' and then setting it on 'backwash' for a minute or so? And then returning where? Back around the front again (clockwise)? Or proceeding anti-clockwise to 'closed', 'drain' and back to 'filter? You're right. Don't want to wreck the mechanism by forcing it in the wrong direction. Bit expensive. Thankyou all for your help.

it doesn't matter whether you move the handle clock- or counterclockwise. important is that the handle is moved always in the same direction in order not to spoil the seal in the multiport valve. one minute backwash is definitely not long enough. there is no set time for backwashing. all what you have to do is watching the little glass cylinder on the drain pipe. as long as the water is dirty, keep on backwashing; that can take up to several minutes.

important:

-after backwashing put lever on "RINSE" for another 30 seconds to a minute. you will still see some dirt. rinse till water is clear and then put lever on "FILTER".

-whenever you change the lever, SWITCH OFF PUMP!

[tamsin]

Don't worry about the setting of the multiport valve for now... it sounds to me like the ball valve on the outlet side of the multiport valve is open... thus dumping the water straight to waste.

The multiport valve should be set to the filter setting, and the handle on the ball valve on the outlet should be in the closed position, ie. at 90 deg to the pipe run direction.

Your gardener probably forgot to close the valve after backwashing (and hopefully rinsing).

Have just asked the gardener to order some more water for the pool and he's looking a bit worried and says maybe the water might 'go away' again. Not sure if he opened the valve to the pipe that dumps the waste or not, he swears he didn't, but. (Now also not sure it was the multiport not being put back on 'filter', think he may have tried to play around with it after the water had already gone, in the hope it might come back ...)

There are three pipes in total.

One to the pump (clear enough) but the other two go straight down into the concrete footing, and not sure which one is the drainage pipe and which to the pool. Will have a big red felttip at the ready when I'm it's crystal.

One has the small clear plastic box to show when water is clear when backwashing (have looked at website, but setup not same), and the other pipe runs both up to a waterfall on top of the pump room, and then down into the concrete bed, and has two valves (for if you want to close of the water feature of course). Before I watch yet another car load of water go down the swanny, which one is the drainage pipe and should therefore have it's red plastic valve closed please? Thankyou.

[tamsin]

Don't worry about the setting of the multiport valve for now... it sounds to me like the ball valve on the outlet side of the multiport valve is open... thus dumping the water straight to waste.

The multiport valve should be set to the filter setting, and the handle on the ball valve on the outlet should be in the closed position, ie. at 90 deg to the pipe run direction.

Your gardener probably forgot to close the valve after backwashing (and hopefully rinsing).

Before I watch another carload go down the swanny, which one's the drainage pipe? One to the pump. One up to the water feature and back down into concrete with two valves, and one with the clear plastic box on the side to show clarity when backwashing, and then also down into concrete (not clear from website diagram which is which). Thanks.

[Jai Dee]

Don't worry about the setting of the multiport valve for now... it sounds to me like the ball valve on the outlet side of the multiport valve is open... thus dumping the water straight to waste.

The multiport valve should be set to the filter setting, and the handle on the ball valve on the outlet should be in the closed position, ie. at 90 deg to the pipe run direction.

Your gardener probably forgot to close the valve after backwashing (and hopefully rinsing).

Before I watch another carload go down the swanny, which one's the drainage pipe? One to the pump. One up to the water feature and back down into concrete with two valves, and one with the clear plastic box on the side to show clarity when backwashing, and then also down into concrete (not clear from website diagram which is which). Thanks.

It will be the "one with the clear plastic box on the side to show clarity when backwashing, and then also down into concrete".

Make sure the handle is set to across the pipe run, not parallel with it. This should then be in the closed position.

[Naam]

Don't worry about the setting of the multiport valve for now... it sounds to me like the ball valve on the outlet side of the multiport valve is open... thus dumping the water straight to waste.

The multiport valve should be set to the filter setting, and the handle on the ball valve on the outlet should be in the closed position, ie. at 90 deg to the pipe run direction.

Your gardener probably forgot to close the valve after backwashing (and hopefully rinsing).

Before I watch another carload go down the swanny, which one's the drainage pipe? One to the pump. One up to the water feature and back down into concrete with two valves, and one with the clear plastic box on the side to show clarity when backwashing, and then also down into concrete (not clear from website diagram which is which). Thanks.

It will be the "one with the clear plastic box on the side to show clarity when backwashing, and then also down into concrete".

Make sure the handle is set to across the pipe run, not parallel with it. This should then be in the closed position.

but make sure to open the valve before backwashing! if some air is in the filter (happens quite often) it might blow up. people have been killed.

[tamsin]

important:

-after backwashing put lever on "RINSE" for another 30 seconds to a minute. you will still see some dirt. rinse till water is clear and then put lever on "FILTER".

-whenever you change the lever, SWITCH OFF PUMP!

um, went through the procedure, no problems, except for when I get to 'rinse' part (bearing in mind the drainage valve is still open). the sandfilter made a gurgling sound and the water dropped again, only about an inch or so, but could empty the pool after a few months. should i close the drainage valve directly after the 'backwash' and before the 'rinse'? or will i cause the thing to blow me up? thanks.

Edited July 4, 2007 by astral

[Naam]

um, went through the procedure, no problems, except for when I get to 'rinse' part (bearing in mind the drainage valve is still open). the sandfilter made a gurgling sound and the water dropped again, only about an inch or so, but could empty the pool after a few months. should i close the drainage valve directly after the 'backwash' and before the 'rinse'? or will i cause the thing to blow me up? thanks.

drainage valve has to be OPEN during rinse! rinse does not work when valve is closed and of course there is the danger that the filter casing blows up there is too much air in it. filter may rupture also when all air is evacuated but then no danger of any injury.

[tamsin]

and the water dropped again because? the rinse was only on for the minute suggested.

[cdnvic]

and the water dropped again because? the rinse was only on for the minute suggested.

I think you might have air in your plumbing which is causing more than normal fluctuations as it works itself out. I have one where the pump and filter is located far away and the result is that the plumbing holds quite a volume of water. Another possibility is a surge tank, but we have really no information about your pool to make an estimate on. Not knowing the volume of the pool and the location of your pump and filter, it's impossible for me to estimate. You really need to know the volume of your pool if you want any hope of keeping the water in balance though.

As for sand filters exploding, I've never heard of that happening....ever. Even Google turns up nothing.

The drain pipe from the sand filter to the concrete should not need a valve on it. When the valve atop the sandfilter is set to backwash, rinse, or drain, it will drain, but if it's on filter then there should be no water going down that pipe at all and the extra valve is redundant.

You need to pay a professional to spend at least a day with you to show you the fundamentals of managing the pool. Neither you, nor your gardener are prepared it seems, and all we can offer you is guesses based on other guesses. That pool is a major investment that could be a money pit or health hazard if you don't learn how to take care of it properly. Spend the money on learning how to manage it and it will pay you back many times over the first year.

[Naam]

As for sand filters exploding, I've never heard of that happening....ever. Even Google turns up nothing.

you are invited to talk to the electrician who did the installation in my home (location Pattaya). his left arm is stiff (multiple bone fractures), caused by the rupture of a pool filter.

no matter whether sand, DE, cartridge filter; any filter or enclosure can blow up when too much compressed air has accumulated. that's why all filters have a valve to release excessive air which also builds up by water degasifying and not necessarily a leak in the suction pipe. in 1998 several states in the U.S. (i know of Florida only) made it compulsory that pool filters are fitted with an additional automatic valve that is triggered if the pressure exceeds a certain preset value.

[cdnvic]

I've specifically queried two manufacturers, as well as other pool managers, including one who has been certifying pool managers since the 70s about this particular possibility and none of them have been able to recall a sand filter exploding. Out of the thousands of pools licenced in this province there is not one case of injury from an exploding filter tank listed with the Worker's Compensation Board.

Yes, you can make the pipes explode if you try to clean them with an uncontrolled compressed air blast, but not by backwashing. I cannot find a case of that happening anywhere, nor can any experts I've talked to.

Edited July 7, 2007 by cdnvic

[Jai Dee]

You need to pay a professional to spend at least a day with you to show you the fundamentals of managing the pool.

Good idea... even a couple of hours would be worthwhile.

[Naam]

Yes, you can make the pipes explode if you try to clean them with an uncontrolled compressed air blast, but not by backwashing. I cannot find a case of that happening anywhere, nor can any experts I've talked to.

you can make the filter or drainage pipe explode by backwashing or rinsing if you forgot to open the drain valve which is normally installed to prevent water loss when the multiport seal is old and damaged. of course, if that valve does not exist (i assume a lot of pools in Thailand don't have one) there is no danger.

[cdnvic]

Yes, you can make the pipes explode if you try to clean them with an uncontrolled compressed air blast, but not by backwashing. I cannot find a case of that happening anywhere, nor can any experts I've talked to.

you can make the filter or drainage pipe explode by backwashing or rinsing if you forgot to open the drain valve which is normally installed to prevent water loss when the multiport seal is old and damaged. of course, if that valve does not exist (i assume a lot of pools in Thailand don't have one) there is no danger.

You're going to rupture a seal long before your sand filter explodes. I'm still trying to find cases where they have blown up (can't find a single one), let alone people being killed as you earlier stated.

Edited July 7, 2007 by cdnvic

[Naam]

I'm still trying to find cases where they have blown up (can't find a single one), let alone people being killed as you earlier stated.

go on trying, i rest my case

[cdnvic]

I'm still trying to find cases where they have blown up (can't find a single one), let alone people being killed as you earlier stated.

go on trying, i rest my case

That makes no sense. Can you show me where someone has been killed or did you just make it up?

[Naam]

This month, a bursting pressurized pool filter knocked a Surprise man unconscious, sending local rescue teams to his aid. He had been cleaning the filter incorrectly, and then his family heard the blast and found him with critical head and chest injuries.

That accident worries emergency squads because it was the second of its kind in recent weeks, Surprise Assistant Fire Chief Kevin Pool said.

All pool filtration systems operate under high pressure and are potentially dangerous, Arizona State University pool technician Joe Zimmerman said.

http://www.sosnet.com/safety/current.stori...lterDanger.html

On April 5, 1997, John Doe was cleaning the pool filter at his home in Lafayette, California. Following the instructions attached to the label on the pool filter he disassembled, cleaned, and re-assembled the pool filter. After turning the pool filter back on, he went into his residence and then returned to check the filter system. While he was leaning over the pool filter canister, it exploded with over 10,000 lbs. of force. The canister hit John Doe in the head and caused him to suffer a fractured skull, fracture to the eye orbit, fracture of two front teeth, right temporal lobe brain injury, brain stem injury, trauma to the cervical vertebrae and facial lacerations. The firm contended that the pool filter's defective design trapped air in a pressurized vessel, which in turn compressed the air.

http://www.veenfirm.com/representative-cas...-and-others.php

WASHINGTON, D.C. (Aug 74) -- The U.S. Consumer Product Safety Commission today warned that almost 50,000 persons will require hospital emergency room treatment this year in accidents associated with some of the nation's four million swimming pools.

The Commission also is considering a variety of approaches that could reduce injuries associated with other pool hazards such as sharp edges and protruding bolts, slippery ladders, decks and diving boards, lack of depth indicators, shock hazards from electrical wiring and problems of exploding filter tanks.

http://www.cpsc.gov/CPSCPUB/PREREL/prhtml74/74056.html

[slapout]

No matter how hard you try or how long you talk, giving your knowledge and experience to Worms, the only way they will learn is to get their hands dirty, clean the pool, filters, add chemical, etc. etc. and then clean up their own mess.

[Naam]

No matter how hard you try or how long you talk, giving your knowledge and experience to Worms, the only way they will learn is to get their hands dirty, clean the pool, filters, add chemical, etc. etc. and then clean up their own mess.

bingo!

[cdnvic]

Ok, you have one accident with a tank that was put together incorrectly. Can you now show me where someone was killed, or even hurt with a normally functioning sand filter? It's just if you want to give out advice you should be able to cite credible evidence. Making up fantastic stories about people killing themselves backwashing a pool is a little unnecessary don't you think?

Edited July 7, 2007 by cdnvic

[Naam]

Ok, you have one accident with a tank that was put together incorrectly. Can you now show me where someone was killed, or even hurt with a normally functioning sand filter? It's just if you want to give out advice you should be able to cite credible evidence. Making up fantastic stories about people killing themselves backwashing a pool is a little unnecessary don't you think?

we could go on splitting hairs but for me it's too boring as i find it boring to google for the incidences i have mentioned NOT "made up".

if it makes you happy then we can also agree that

quote: "...a fractured skull, fracture to the eye orbit, fracture of two front teeth, right temporal lobe brain injury, brain stem injury, trauma to the cervical vertebrae and facial lacerations"

is something to take lightly as it happens to each of us pool owners quite often.

as far advice is concerned... those i gave are well founded. i don't poke my nose, make and insist (even after receiving the facts) on irrational statements like "air in the pipes"

if the water level in 60 m² pool drops 1' (30.5cm) then we are talking of nearly 2,000 liters or 530 gallons. one should switch on brains, do a mathematical estimate what pipe length is needed to take that volume before making these kind of statements

to sum it up: you Honourable Sir have no idea as far as pools are concernded. but as far as "no idea" is concerned you possess a lot of it and the same goes for your maths.