So you have the plumbing picked out, pipes, fittings and glue along with the general paths you are going to take. Ensure you measure everything carefully; get a couple of extra fittings in case you need to make adjustments. Now it’s time to ensure that your system will work – have you considered everything?
Valves: You will need to place shutoffs and check valves in your system. Remember, check valves go after the pump (never before) and they have a specific orientation. Ensure to install them properly. On all valves, I install them with slip unions to either side. That way, I can remove and replace them if necessary as both have moving parts and could fail. The check valve should be placed near the pump discharge. However, I have found that just after the pump, and just before the check valve, I like to place a tee or wye that leads to a shutoff then immediately returns back to the pond (no head height). This is a “bypass” line. When opening the shutoff, the water will have a choice of paths – back to the pond or up to a filter, waterfall, or back to the beginning of a stream. Noting that there will be more static head pressure after the check valve in most situations, the water will take the bypass route instead. This allows you to turn off a filter or water feature during cold winter months, maintenance, cleaning or even to isolate leaks. I would NOT advise putting a shutoff on a single discharge line after the pump (or multiple shutoffs on multiple discharge lines). This could lead to a mistake where you inadvertently close all the shutoffs which could damage the pump. Note that the check valve and bypass valve will be in the housing with your pump so all the controls will be in one place. I installed this configuration in both my skimmer box for my submersible pump, and within and my external pump vault. My auto-refill valve and overflow are in my skimmer box, while my drain valve passes through my external pump vault.
Drains: Maintenance, water changes, replacing components, or cold weather may require the main pool, filters, skimmers, waterfalls, etc. to individually drain water from them. This could be as simple as a drain plug, a valve in the bottom of the component, or you can get a bit creative. In my system, I have a 150 gallon stock tank which serves as my sludge pit AND my bio-filter above. This size can handle a 4500 gallon pond. My skimmer pump discharges into the bottom on one side and my external pump discharges into the bottom of the other side. The top of the tank sits 5’ above the pond surface (and is 2’ deep). Just before the external pump discharge line reaches the tank, I have a 1” bleed tee that runs back down to the external pump vault. If I open the drain valve, as the pump runs, water is bled off the discharge lowering the water in the main pool. If I open both the pump bypass valves, water in the main pool remains the same, but the bio-filter tank empties. If I want to drain the skimmer, I need only to lower the main pool a few inches and let the pump drain the box (I have an electric switch that stops both pumps in my main pool and skimmer box so that do not run dry). The single drain line dumps into my waste system.
Fill Line: Although a hose will work, a dedicated line has many advantages. First, a pipe or hose can be buried from the source to the pond. You can also add a number of features that will greatly assist you. In my system, I put a brass wye with shutoffs on my spigot at my house. This way, I still can use my garden hose freely. The other side has a water meter and timer. The water meter is a must for water changes, measuring gallon capacities and in general, how much water you are using due to evaporation or alerting you to leaks. My fill line runs underground to my skimmer box. I installed two bulkhead unions in the back of the box. Bulkheads have internal threads, so I also bought an auto-fill valve to keep the pond topped off (this only has a 1GPM). With the other, a screwed in a brass hose shutoff for major fills (my manual fill valve – which rates 4GPM). They both can easily be removed. This gives me great control of water fills.
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