Pump fed but going deeper...

wellsi · 21-02-2012, 11:29 AM

Hello again guys

After last week's discussion on pond depth and a rocky winter with some nasty temperature swings, I've decided to bite the bullet and deepen and reline our 2000 gal pump-fed sunken pond. The advice on here is that it's too shallow for our 6 large (20”) koi and 15 or so smaller koi & goldies and not enough to stop the temperature swings, especially in spring and autumn, let alone winter.

I'm not in a position to build a new gravity fed pond, due to finances and the landscaping we have, with the Nexus 210 in a shed some 20 feet away from the pond: (the return is via a rock stream / waterfall in summer and a 3” buried straight pipe in winter).

I'm going to use the separate 750 gallon smaller adjacent pond to house the fish for the week or so, as I can empty it, refill with existing pond water from the main pond, then transfer the fish, pump and return into it. Then drain the main pond, dig deeper, reline, then refill.

Main pond is 21’ long, 14’ wide and a just 30 inches deep. We're going to deepen half the pond to 4 & ½ feet, with a slope up to a 3' the shallower end where the water fall returns. This will give water flowing into the shallow end, down the slope to the deeper end, where a retro-fit bottom drain will pull the water and muck via the pump to the Nexus. Should be around 3500 gals.

Anyone got any thoughts or advice, especially on a more powerful pump that isn’t a fortune to run but won’t block too often? And any thoughts on timing? Pond is currently heated to 8’c; was planning to wait few weeks to let it get up to more 12’c…

Cheers as ever

Ian in Essex

Doghouse Riley · 21-02-2012, 11:58 AM

As I often say "each to their own" but why go down only to four and a half feet? With fish that size already I'd want it at least five feet or more, the cost wouldn't be that much greater, "writing it off" over many years, certainly when you consider the life of a koi pool.
I'd suggest that the temperature swings in any pool will have more to do with the total volume of water than the difference in depths by a couple of feet.

We've really not enough detail here,
If you're more or less starting again, why not install a proper bottom drain?
I know it's easy to make criticisms, but we all make mistakes and there's a tendency to "want to get it done and finished." I certainly have had to try to stop myself on occasions, but I guarantee that most would say in the same situation, that you'll regret later not doing it properly.
If it's a question of expense I'd suggest it's far better to wait until it becomes affordable.

Anyway, 20ft is a long way to pump water.
I'm sure you're aware that the efficiency of any pump is reduced by how far it has to pump the water, how many bends there are in the pipe and the head height it has to achieve.
I presume you're presently using a submersible?

I'd recommend an Oase for durability and efficiency they can handle coarse solids.

To get an effective rate to make a visually attractive waterfall, I'm sure you know that you need a reasonable volume of water, but you don't want so much that the "dwell time" of the water in your filter is reduced to the extent it isn't as effective as it should be.

This will give you an idea of performance and running costs of the various models.

Edit. The running costs are way out given the unit price of electricity quoted.

Oase Aquamax Pumps

the stoneman · 21-02-2012, 02:09 PM

Hi Ian,
I see that you are near Chelmsford, I live in Chelmer Village. I suggest that you get out and look at as many ponds as you can before you start. If you want to pop over and look at my setup, you are more than welcome. PM me and I will give you my address.

Cheers

Peter

Davej · 21-02-2012, 06:22 PM

Hi Ian

I'm not gonna give you a lecture about the desirability of a BD.

But if it could be done then it would save having a load of clutter in the pond.

4'6 would be ideal, if you go any deeper with the surface area you are looking at the volume would start to get such that you are having to run more filters, with more expense etc.

Best done sooner in the season rather than later, moving them at 10-12C isn't a great problem - but do your planning.

I'd suggest an Oase pump in a dirty water situation, Superfish are cheaper but the impellors are not up to crunching any debris, with 2" pipe the 20 feet run shouldn't be a great issue. If you go for flexi pipe then you need alfagoma or equivilent.

Dave

wellsi · 21-02-2012, 11:04 PM

Thank you gentlemen....
Yes, I'm wary of going much deeper; it's an odd shaped pond but I'm not wanting much more than 4000 gals; that's plenty big enough for me.
I want to have a deep pit with sloping floor towards the centre pit, so the rubbish goes towards the deep part. Happy to use my pond-vac occasinoally for whatever the pump / retro-fit BD doesn't clear.

Having the pump near the bottom should be ok; I mentioned to doghouse that physics states it makes no difference to the vertical head whether the pump is just below the surface or at the bottom of the pond; my vertical head in either case will only be around 3 foot. But with the distance, friction does come into play; no sharp bends and it is indeed alfagomo hose that I have.

i'm sure this may well be stage 3 of the ongoing fun of upgrading and rebuilding, but hopefully this will give my existing fish the depth they need with a decent filter system too.
Cheers for the pointes on the pump; the single biggest problem with pump-fed is the clogging, so if Oase are good at this, I'll probably go for that.

One final point though; I do hear you on the BD issue; is it possible to have pump-fed with a bottom drain? Is it achieved via housing the pump situated above the pond? If so, is the only advantage the lack of a hose and pump in the pond or is there more benefit I'm missing? Sorry for being a bit slow on this point....

Cheers
ian

Davej · 22-02-2012, 12:13 AM

Hiya

Yes you can go bottom drain and pump feed your filter but this would not give you all the benefit of a gravity fed system.

Main issue with a pump fed system (with or without a BD) is that the pump blends up the muck into soup which makes the mechanical filtration more challenging.

Dave

wellsi · 22-02-2012, 07:14 AM

I can see why most people's ponds are 2 feet above ground; ours is completely sunk so the water level is 6 inches below ground level; it's desinged to look like a natural pond and I'm v reluctant to build a collar to raise the water level.

Am I right in thinking that with a ground level pond, gravity fed is only possible if all the filtration is below ground level as well? In which case cleaning becomes a night mare too; we're not on mains drainage; our loos go itno a septic tank and pond sludge goes into the field next door..... hence my Nexus needs to be above ground...

All good fun....

Davej · 22-02-2012, 09:20 AM

Quote:

Originally Posted by wellsi

Am I right in thinking that with a ground level pond, gravity fed is only possible if all the filtration is below ground level as well? In which case cleaning becomes a night mare too; we're not on mains drainage; our loos go itno a septic tank and pond sludge goes into the field next door..... hence my Nexus needs to be above ground...

All good fun....

Yes you are correct.

One way around it would be to link a gravity BD into an external chamber (sunk to pond level) and then take the feed for the above ground Nexus from here, that way the barrell or chamber acts as a settlement chamber for the heavy waste which you can pump out to clean. Doghouse Riley uses such a set up and in your circumstances would seem a practical way of solving things.

Dave

I

Doghouse Riley · 22-02-2012, 09:58 AM

Above ground pools seem the most common variety these days, I don't know what came first, the desire for this type of facility or the filters that are more suitable for this arrangement.

Before I got into koi, in the mid eighties, I visited several pools in the North-West area and all were surface level and "natural looking" which was my choice, but it does restrict what sort of filter arrangement you can employ.

Ned · 22-02-2012, 10:44 AM

Quote:

Originally Posted by Davej

Yes you are correct.

One way around it would be to link a gravity BD into an external chamber (sunk to pond level) and then take the feed for the above ground Nexus from here, that way the barrell or chamber acts as a settlement chamber for the heavy waste which you can pump out to clean. Doghouse Riley uses such a set up and in your circumstances would seem a practical way of solving things.

Dave

I

Or sink the filter for gravity feed and pump to waste.