Hi Guys.
I need some advice on this please.

I installed a sadfilter (3 bagg ) with a .75 Kw pump about 4 months ago.
in addittion to my 3 Vortexes and a serious bio filter running also on a .75 Kw pump. all this gave me cristal clear water.

Initially I could see a lot of muck when I backwhashed it, but for the last month or so, none. But when you get your hands in there then alot of dirt comes out. So I decided to install a blower point for my compressor. during the testing I noticed that the air and water only comes up in the one area and not everywhere, so 3/4 of the sand does not get cleaned. I then thought a spider leg has broken of and removed all the sand to check, but no problem.
My question now, is it perhaps because the filter got too clogged up that it wont backwash properly.
Will it help if I filled the bottom to say 100mm over the spider pipes with say 20mm crush stone before I place the proper koi gravel.
Or must I just except that I have to clean thie filter more regularly by hand.
My whole system is holding about 30,000 liters and I have in total 55 fish averaging around 45cm.

Neville, you beter ask the SF

I clean my sand filter twice a week in summer and once a week the rest of the year and never have any problems. By cleaning i mean, open the top and stir the gravel while the pump is on back wash.

I know Chris Neaves uses 2 jacuzi blowers on his sand filters. Maybe ask him aswell.

Thanks wayneb
That is more cleaning than what I have been doing to date.

I hope the SF King will talk to me as well as Chris I am sure there experience on this subject is vast

I usually clean my filters on Wednesday and Saterday/Sunday in the summer. And only on a Saterday/Sunday in the winter.

In summer the amount of waste generated by kois are more than in winter. And i find that if i do it twice weekly i do save a bit of water as cleaning a sand filter without one of those fancy pressure machines do use quiet a bit of water. I estimate that i use about 1500 liters of water to clean my sand filter.

I also have to point out that my sand filter is not my primary mechanical filtration, its more of a polisher as i have a settlement vortex and eazy as pre-filter before my sand filter.

The SF cleans his Sand filters properly once a month the rest of the time he does normal backwashing (swimming pool style).

Pieter J de Villiers wrote:

Hi, I clean my Ultra Zap Bio Filters once a year in August, the sand filters are back-washed every second day and once a month I open and “turn” the filter. http://koionline.forumotion.com/equipment-f31/how-often-should-one-clean-biological-filters-t677.htm

Wayne

Hi Neville,

I do not think you air blower will have enough volume and power to use on a sand filter. Its not that you arms are broken at the bottom its just that it does not have enough power. Air blowers are fine if you want to bubble a few plastic things around in the water.

If you use a Zuccuzi Air blower things change. Sand filters are very easy to back wash.

Picture below - One Zaccuzi air blower for two sand filters. When air bumping the system use one sand filter on closed and the second on back wash



You then get this effect - even after you have back washed normally. So the sand bed gets a good tumble and the trapped solids are released.



The sand bed is lifted and broken up. Your sand filter flushes the trapped solids to waste and is easy to clean.

Chris

Hi Jan

On sand filters the pump used is mainly of concern when it comes to cleaning it. The pump needs to be strong enough to lift the sand during back wash. In the filter operation a smaller pump can be used but dont expect the same "force" of water to exit the sand filter as a biger pump.

I think for a 3 bag sand filter a 0.75kw pump is optimal, bigger is better ofcourse but one has to take the running cost into considuration.

The general configurations are as follows:
2 bag Sand filter - 0.45kw pump
3 bag Sand filter - 0.75kw pump
4 bag Sand filter - 1.1kw pump

I myself have been using a 0.45kw on a 3 bag sand filter for almost 3 years now and i dont have any problems but im sure a 0.75kw would make the cleaning of it easier.

Wayne

Hi Neville,

Please contect me by PM.

I am willing to visit you and solve the problem.

Hi Pieter

Baie dankie man ek waardeer dit terdee ek sien uit om jou daar te he

Baie dankie

Hi -

Because a sand bed is a very efficient mechanical filter media you can also help the situation by reducing the amount of gravel/sand by about a third. You will still get excellent mechanical filtration and the pump will not have to lift so much weight.

Substituting zeolite (much lighter than sand) for the sand also helps.

Waynes ratios between pump size and the number of bags is correct and very important. One often finds a large sand filter coupled to a small pump and the owner does not know why it is not back-washing efficiently. False accuations against sand filter use on koi ponds are then made.

It all comes down to how things are designed and how they are used.

Chris

Hi everybody,
Many thanks to all of you for the response received to date. Sometimes one just cannot understand why things don’t happen the way you envisaged and then it is nice to get advice like this and I am sure a lot of other people also benefit from it.

To summarize at present

It seems that I just have to clean more often
I still would like to place larger stone at the bottom to a level above the spiders.
I am wondering if more vortexes would not have been a better idea for my setup.

Then
Chris, thank you for your comprehensive explanations. I really thought that the reservoir capacity would do it but it seems that one needs the air for a longer period to really clean a dirty filter, easy to change though.
Bobby, man I have one of those HP cleaners don’t know why I never thought of it.
Wayne thanks for your input and fast reply gee 4 minutes (man dit is amper vinniger as wat n mamba pik), dankie.
Jan, jammer oor die tikfout, is jy afgetreede onderwyser? Ek sal van nou af “word” gebruik en eers n spelcheck doen. L.O.L.

Hi Chris

While were on the sand filter subject and based on your article, use and abuse, of sand filters on the website koi4u.co.za I have the following question.

http://koi4u.co.za/index.php?option=com_content&view=article&id=23:use-and-abuse-of-high-rate-sand-filters-for-the-21st-century-koi-keeper&catid=6:chris-on-koi&Itemid=33

I have a 30000l pond. I have used for filtration a 2 bag filter with a .75 pump. 1-25l Bio-chamber filled with looli tubes and 1-30w UV Light.

The pond was running for 3 years but the system did not work.

I am now in the process of upgrading my filtration system on a sadly restricted budget.

The new filtration will be:
1 x 1,1kw pump (not sure yet)
3 x 3-bag sand filters in parallel
1 x jacuzzi blower
2 x 65l bio-chambers filled with plastic bio balls
2 x 30w UV lights

Will this be sufficient or not? Will a 0,75kw pump be sufficient or do I need to use the bigger 1,1kw pump?

I will appreciate your inputs.

Hi pierre

The main thing on big ponds is to have enough flow and circulation. If the water is not circulated enough the pond stays dirty. How many suction lines do you have and how many returns? I have 4 returns and 2 suction lines on my pond.

I use to run 2 x 0.45kw swimming pool pumps on m 32000l and have now scaled down to a 0.45kw and a 0.25kw swimming pool pump.

Go and calculate what will give you the most flow at the lowest cost per month.

a .1.1kw pump gives you a max flow of 30 000l per hour.
a .075kw pump gives you a max flow of 24 000l per hour.
a .045kw pump gives you a max flow of 18 000l per hour.
a .025kw pump gives you a max flow of 10 000l per hour.

Something that you must remember is dont return the water at the same end as where you are sucking from. Take the water from the BD and return it via maby a waterfall at the opposit side of the pond and then take the water from the skimmer and return it via under water jets on the opposite side of the skimmer. That way you are sure that you are circulating the water enough.

Hi Pierré,

The biggest disservices to koi keepers occurred a number of years ago when a concept was marketed and sold that a single sand filter can be placed on a koi pond – but that’s another story.

Yes a single sand filter with a ,75 kW pump on a 30,000 L pond will not work – why? For the simple reason is that a single sand filter restricts the amount of water you can turnover to the point that the organics and solids build up in the pond faster than they are removed in the filter system. And yes, this can vary greatly from pond to pond.

There are other factors relative to filters/pumps and pond volumes – things such as stocking densities, feeding rates etc. But let’s be honest the average koi keeper is not going to sit at the pond and calculate the size of his fish, the number in the pond, the protein levels of the feed, the amount of feed give each day etc. etc. If you are like me – just set it up right and sit back and enjoy your hobby.

Question – have you bought the pump yet? If not, then seriously consider Speck above other pumps. They seem to be hardier and definitely have more punch (for the kW used) also they definitely deliver more water than other equivalent pumps.

For example a speck BHS 20 is a ,75 kW pump and gives you 27,000 litres per hour. The BHS 25 is a 1,1kW pump and gives 33,000 litres per hour. These are figures in unrestricted use.

What Wayne has also pointed out - the pump size relative to the filter size is important. If the pump is too small then it does not backwash the sand bed properly.

Your 3 x 3 bag sand filters in parallel will work very well. This was the great misconception of sand filter use on a koi pond – one sand filter is OK for any size pond. I have seen gigantic filtration systems that are not working. In many cases the answer lies at the end of the system in a single sand filter to “polish” the water. A single sand filter has the multiport valve this is 32 mm if I recall correctly. Then you have a very efficient sand bed which further restricts the water flow. Added to this, once the organics build up (which they do in ALL filters) you have further restrictions on flow rates. Yet all this time you are drawing the electricity to drive the kW on the pump you have chosen – but you can easily loose 40% of your flow rate through restrictions.
So roughly 1 sand filter per 10,000 litres will work. I use the cross section of the filters i.e. 1 x 30” sand filter per 30,000. Although 1 x 24” sand filter per 10,000 litres also works. Secondly the gravel you use must be 3 – 5 mm. Then if you want to – substitute the gravel with zeolite.

Another point to consider – piping. 50mm piping is very restrictive of flow rates as are 90 degree bends. 2 x 45 degree bends is much less restrictive. I am not sure how you are setting up your system but in the suction line to the pump you must go for a minimum of 63mm piping. Then on the out let it must also be 63mm piping. Where you T off to the sand filters reduce to 50 mm. This is 3 x 50mm into the sand filters from the main line of 63 mm. So your restrictions will be overcome. You then have three 50 mm out lets which can be direct where you want - to a water fall, stream, creating circulation in the pond etc. With a water fall you do not need a venturi by the way.

You can then feed the three outlets from the sand filters to three biofilters. Although please take into account that the sand bed is already a biological filter as well. If you feel you need UV lights then place them after the sand filters and after the biofilters.

Working on a turnover of about the pond volume through the filter system in under two hours I recon a ,75kW Speck pump will work very well providing you have tried to eliminate all possible restrictions.

Another tip – I do not know the design of your pond but do you have a surface skimmer?

Chris