Piping Questions

17500 gal pool 1hp pump S210T (44 gpm) ....I am hooking up a pool heater (jandy 250K) and the CPVC nipples they give you for entry and exit are 2".....

Skimmer and low suction fitting were going to be piped in 1 1/2" thru pump and filter....can I upsize to 2" for the heater and then make the return (2 returns) 2" or should I stay with 1 1/2" the whole way?

Also....is an equalizer valve a code requirement on the suction side or is just a good idea? Should I take two suction lines both off the skimmer since I have two ports in the skimmer bottom?

Topnotch, welcome to the forum:) !
The company I work for runs the lines to and from the pool 1 1/2", but steps up to 2" across the filter system, the main reason for this is because the Northstar pumps, Stay-rite (now Pentaire) heaters and Goldline SWCGs all have 2" unions and reducing into each one would be a PITA - the 2" also let's us counteract some of the flow reduction caused by the 90s and 45s, filter and heater. Duraliegh, a respected member here, has advocated, running everything 2" (the price increase is marginal), which is reasonable but not essential. At some point you'll need to reduce to 1 1/2 to get through the wall.
The only time I put a check valve on the pump's intake is when the filter system is over 3' higher than the pool, the Nothstars we use can easily pull 3' of air out of the line to prime. If you go with a check valveyou will want to 1) upsize the pipe to 2" as the valve reduces flow some and 2) Install a union on the pool side of the check valve so that you can blow out the lines in the fall. Codes are set by the local government so you'll have to check that for yourself.
I would not try to plumb both ports of the skimmer into the pump, the second port is for plumbing a MD trough the skimmer :eek: , installing a ballance line (if the water gets too low and the skimmer would suck air, the ballance line is supposed to keep the skimmer filled with water, unfortunately I've never seen one keep up with the pump) or install a 'reserve' line run to the filter but not plumbed into the system so that if something happens to make the original skimmer line non working, you already have a new line installed and ready to be plumbed in. I have the feeling that trying to run suction through both ports of the skimmer would cause the skimmer to draw air because the pot wouldn't be able to fill fast enough, but this is just a gut feeling I cannot see any advantage to having both ports sucking. Good luck with your pool, if you have any further ?s, ask away and someone here will do their best to help you - Waste

SO

Using only the skimmer for the intake is fine? I had heard it was a good idea to have a separate suction line low in the wall for the vacuum.

My GPM's all seem in order...the pump sends about 80 gpm with a minimum head and the filter will allow 44 gpm and the heater works between 30 and 125 gpm......seems like all i am really needing to do is supply the heater with enough water, right?

Sorry, I thought from your first post that the low suction was going to be part of the plumbing, you should have at least 2 suction sources (** for AG owners who read this - your system is fine, all plumbing is easily acessable**), if one goes bad you can still run the pool off of the other, and it helps keep the pump fed. Yes, the numbers look in order, the heater won't fire if there isn't sufficient flow to 'trip' the pressure switch.