The Bottom drain (as it has been called) should not be confused with an outlet to the sewer (that is how they used to be used when they first were introduced to the Koi keeper quite a few years ago) Now it has the one main purpose, and that is to transfer all the water and all waste products from the bottom of the pond to either a 'Prime Vortex Unit' (Which is Highly Recommended) or if you wish then direct to the Filter Units themselves.
If you intend to install one, or more bottom drains, into your new pond then please bear in mind that they must figure early in your pond construction program - as the sump and the 4" or 110mm pipe which transfers the pond water, and debris, into the mechanical filter, possibly a Vortex unit, which are extremely effective will be set in concrete as you lay the base for the pond floor - and therefore plan your pond carefully and don't rush or cut corners ... and bench (slope) your floor towards each bottom drain... and round off any corners to give a 'Good Water Flow' and circulation round the pond which will then move any debris on the pond floor towards the bottom drain...
The pipe work from the bottom drain to the 'Vortex' can be done in solvent weld (black waste) pipe if you wish - but we strongly recommend that the sections that are 'Under' your pond base are done in PVC pressure pipe which is much stronger and as the name implies can withstand pressure... although more expensive - believe us it is worth it ..and you will certainly have peace of mind when is comes to trying to find that leak somewhere in your pond ... as surely can happen in many cases of D.I.Y. pond construction ... so please don't take the risk ..
Another tip when you are installing any pipework that you are going to glue (solvent weld together) is to always try the bends, connectors and joints together 'DRY' (without solvent cement) to make sure that they fit and do not need any adjustment ... as once you put the two surfaces with the solvent weld cement on and they touch - they bond almost immediately and it is then impossible to correct any mistakes .. So lay the pipework from the Bottom Drain level until it is clear of the bottom of the pond floor and mark each connection, bend or whatever, with a black marking pen so that you know exactly where they fit and when you do use the solvent weld cement that you have a guide to work to so you do not make any mistakes, hopefully.... If you are at all unsure what you must do then please email us and we will try to help you understand the process more...
Please take a look at the diagram we have provided here to get a better understanding on how a bottom drain fits into the pond construction.
You can, of course use a Bottom Drain with either a concrete base to the pond or a Liner! The Bottom Drain should have been supplied with a special liner flange which is then screwed down into place and which 'traps the pond liner' and holds it firmly in place - if using a liner then a sealant must also be used - we recommend 'Polyflex' for this job which is a black polyurethane silicone type product or a good waterproof, non toxic mastic such as our ERK Gold Label sealant...you will find both these products on our sealants and adhesive page. Both the top and bottom surfaces of the liner flange must be sealed before screwing down with stainless steel screws.
Where possible the bottom drain sump and the pipework should be set in a trench and filled up with concrete to make sure that it is held firmly in place, another tip is to use a bradawl or a similar sharp and thin pointed object to locate the position of the holes in the flange through the liner .... and use a sharp Stanley knife to trim any excess liner off with the inside edge of the bottom drain - do not over tighten the screws as you need a good layer of sealant on both the top and bottom of the liner ... the sealant will ooze out and can then be wiped off and smoothed away to provide a nice neat job.
Of course if you are setting your bottom drain into a concrete base then you will not have this problem and the separate flange that comes with the bottom drain can be discarded as it will not be needed ... Remember though it is impossible to seal plastic to concrete, so you will need to seal the outer edge of the rim of the bottom drain to the concrete. You can do this by using our Fibre Glass Paste, the job is extremely easy and will give you a permanent bond and it is not expensive and will always come in handy, use this also for sealing round your pipe returns through the walls of a concrete pond construction or you can use our ERK P5 Putty.
Both these products will harden rapidly and both can then be smoothed off if required using sandpaper to obtain a good finish ... This can then be painted over using a good quality pond paint such as our own and highly recommended ERK P1 Pond Coating.