I also remember you mammabird. I usually don't use the forum much in the winter but come back on in the spring just to catch up on what's new etc. I have a retrofit bd as well mine is some modifications on the Tetra through the liner drain (which froze) but I used the cap from it for my drain. I am replacing that this year with the Aqua Art Drain as it sits flatter than mine. Not sure if I understand your "hump" but you usually put the bd in the deepest part of the pond. Avid koi-keepers like to do TPR's--but that also means cutting a hole in the liner. With your pond dimensions you might want two bottom drains one for each deep section. That would mean two bulk heads (I did pipe boot connections) through the liner on the side of the pond wall nearest your settling chamber. My drain has a 4" line reduced to 3" just before it enters the sc followed by a 3" knife valve (there much cheaper!). I take my drain out for winter because of my climate. Water inside pipes in my climate not a good idea. My settling chamber is a liner chamber (kinda like a pond beside the pond)350 gals-my pond is 2500 gals. They say sc should hold at least 10% of your pond volume. I really like this system as use sc for water changes. I have 3-4 ft square matala mats in my chamber which is also my mechanical filitration. Good luck with your new pond and move. Patti

It is virtually impossible to install a liner without folds somewhere. If there are many hands and strong backs available they can be reduced but not eliminated. As you have discovered, gentle slopes are less likely to produce big folds than steep vertical sides but they still produce folds or ripples. Folds on the sides are preferable to folds on the bottom.Less stress is produced on the liner if the material on the sides is as perpendicular to the bottom as possible but to avoid the worst folds the material often needs to be perpendicular to the top edge of the pond. This is often contradictory and you simply have to adjust to the situation and make the folds as small as possible even if there are more of them. Gentle steady pull can flatten out some small folds as the water rises. The least problem with folds would be with a circular, gently sloping pond. The worst would be with a rectangular or square shaped pond with abrupt changes in depth and straight sides. Sharp folds with stone leaning against them would be far more likely to wear and tear without the back pressure of soil behind the material I really don't recall this subject coming up over the last several years although it is certainly something everyone has to deal with and I don't recall anyone suggesting the use of foam. I can see a problem or two depending on the way you use it. Applied to the inside of the liner it will constantly be trying to rise to the surface which could cause the liner to rise as well and form hippos or at the least, air pockets or bubbles in the liner sides which puts extra stress on the liner. Since I am not an expert in liner folds I hope someone out there who has put in several liners can give you better answers than I can. I would be very interested in knowing some facts rather than speculation. Sandy

dang it....I had a really well though out response all done, and my internet explorer crashed. So I'll try again...lol!! First...a few comments regarding how koi ponds compare to aquariums. Normally, aquariums are lightly stocked with small fish. It's really easy to keep the ammonia/nitrite/nitrate cycle operating perfectly in a correctly stocked environment. Same as a rock bottom pond...lightly stocked and properly maintanied it can work. In a pond's bio filter, ammonia is converted to nitrite and then to nitrate. Nitrate is most easily removed froma koi pond by way of regular water changes. Ever try to keep an aquarium with goldfish? Many goldie keepers I know keep no gravel in the tank at all, because of maintenance. That gravel gets really filthy very fast. I had a lovely goldie tank once....and gave it up. the maintenance was a nightmare! I'd rather deal with a huge koi pond any day of the week. Some people are reporting sucess with rock bottom ponds and no maintenance. Again...it is directly related to stocking levels. I hope these ponds continue to perform well for years to come, but for the vast majority of people, they will not. Most watergardeners install their ponds (and rocks) and then run out and buy a bunch of adorable little 5" long koi. The koi grow.....fast. They produce mountains of fish waste, which all gets trapped in the rocks. But because the pond looks clean, the owner is lulled into a false sense of security and does not think that there is a thing wrong, until the fish start dying or the fins start rotting off. Then they do one of two thing....they learn where they went wrong and correct their mistakes, or they just buy new fish (which is unfortunatly what most people do). Matt...you are on the right track with your new pond. You certainly can install your bottom drain now and add the rest of the system later. But instead of using a pipe cap, install a 4" ball valve on the end of the line. The water can't be permitted to sit stagnant in the unused drain line for too long or it will start developing the dreaded hydrogen sulphide gas. Opening that valve every couple of weeks and allowing the water to flow out for a couple of minutes will prevent the problems. I am attaching a link to the Atlanta Koi Club's web site. They have an excellent pdf that explains a lot about how a koi pond works, water quality, stocking levels, how much biofiltration is needed and many other wonderful facts. Cindy

Thanks waterbug_guy and mike_il! That's I'm here - you folks are smart. The events of the past few hours have certainly shown me that you are both correct about the source of the water. I don't know what the heck I thought I was doing with my testing, must have read my yardstick wrongly. At daybreak tomorrow, I will be digging out a cubic yard of pea gravel into two large trashcans and get to the manifold at the bottom of the filter pond. No doubt, it's leaking at up there. All of my plumbing is now exposed, so that's not it. It's leaking like a pig now when the pump is running. I can't even get the waterfall to flow with the pump on, put I but my hand in front of the pump and it's pulling water, so all that water is getting underneath. A close look with a flashlight tonight showed damp ground all around the upper pond at the base of the dirt build-up. This explains a lot of things - wet vegetation around the pond, a shrub that died where the water is accumulating, and the waterfall has been a bit less powerful and tonight it"s just a trickle (pump off now). Big question: I've always run my pump 24/7. Will the fish be okay for 24 hrs with no aerating waterfall, or should I go out and buy a fountain or take my oxygen tank from my welding kit and bubble some O2 up? I will post some pictures tomorrow so you can all see my leak.