Spa & Hot Tub Plumbing Repair Tips

Spa and hot tub plumbing is made up of PVC pipe and fittings. It's a closed loop, similar to an electric circuit, if that makes it easier to understand. The same drop of water can make this trip several times per day. But sometimes water can escape the loop, finding its way into cracks and crevices no larger than 1 mm, and dripping on the ground, beneath your spa. Hot tub plumbing repair more commonly involves the equipment (pump/filter/heater/purifier), but a bad glue joint, leaky union, or cracked pipe could have also brought you to this page.

Hot Tub PVC Plumbing Saws

If you walk into any hardware store and ask for a PVC saw, you're gonna walk out with a basic hacksaw. Or you can pay more for PVC saws that resemble small wood saws. Both will cut through a 1.5" PVC pipe in 15 strokes. However, many times there is not enough room to position a 15-18" long saw to make a complete (and straight) cut on the pipe.

That's why I almost never use hacksaws or PVC saws when I do hot tub plumbing repairs. They just don't fit very well under the cabinet, with pipes so close to the shell of the spa. And forget about using them on an inground spa pipe repair, they are even more cumbersome when you're upside down in a hole.

Also useful is a cable saw, a length of picture hanging wire with two handles that cuts right through PVC. A cable saw can be wrapped over an extremely tight pipe and cut through in 25 strokes.

Hot Tub PVC Pipe and Fittings

Pipes 

There are two types of Schedule 40 PVC pipes used in spas and hot tubs - Flex and Rigid. Flex PVC pipes are used for the return manifold, so that the pipes can bend around the spa to all of the spa jets. Rigid PVC pipe is used on the suction manifold, or the pipes from the skimmer and drain to the pump. Be sure to buy Schedule 40 PVC pipe (not thinner walled Schedule 20, used for drainage).

Avoid using flexible PVC on the suction side, because the ribbed pipe has much more friction loss than smooth, rigid PVC, and because it can collapse under extreme suction vacuum. So, use flex pipe up top, and rigid pipe down below, got it? 

Most spas and hot tubs are plumbed with 1.5 inch PVC, although larger spas may use 2 inch PVC. The outside diameter of 1.5 inch PVC (if you were to measure across it), is actually closer to 2 inches, or 1-7/8 inches, (with an inside diameter of 1.5"). 2 inch pipe has an OD of 2-3/8" (and an ID of 2"). The air line (the smaller pipe above the return pipe), is usually 1" Flex PVC, or sometimes 3/4" Flex PVC.

Fittings: 

PVC fittings like couplings, Tee's, 90's, 45's, unions, MTA's and FTA's (male and female threaded adapters), are common at most home stores or a good local hardware store. You can also find good prices online for plumbing fittings.

Be sure to use pressure fittings, which will have a deeper socket than drain fittings. Bathroom drain fittings often have a glue-able surface of about 9/16", but pressure fittings allow you to glue the pipe up to 1-1/4" deep. Drain fittings are never suitable for spa or hot tub plumbing. And like with PVC pipe, be sure to buy schedule 40 PVC fittings, not the thin-walled schedule 20 PVC.

Grey fittings are often made of CPVC or if much thicker, Schedule 80 PVC, both of which are more heat tolerant, or heat resistant. These can be useful when making connections in and out of a spa heater, but are not required.

Spa jet fittings or spa manifolds are specialized fittings that you won't find at your local home or hardware store, but we have all you need!

Glues and Sealants for Hot Tubs

For smooth PVC pipe and fittings, PVC glue is used to bond smooth pipe to smooth fitting, but is not used on threaded fittings. Use only fresh medium or heavy body PVC cement. Old glue that's been in your cabinet for a few years is not going to save you time or money!

Another important distinction exists about PVC cleaner and primer. Use a cleaner for flex pipe, to remove the slick surface, but not overly soften the surface. Primer also functions as a cleaner, but it rapidly softens (decomposes) the pipe, generating heat for a stronger bond. Flex pipe is too soft already, and primer softens it too much. So remember, cleaner for flex pipe, primer for rigid pipe (and fittings), just before you apply the glue.

For a threaded PVC fittings, you need thread sealants. Spread a layer of silicone over the male threads, then wrap several times with Teflon tape. Hand tighten the fitting in as far as you can, and then give another full turn with channel type pliers, or a strap wrench.