Pump Suction Union - Gasket or no gasket?

mts37

Bronze Supporter
Sep 20, 2016
33
Whitehouse Station, NJ
I need a new pump union on my pump suction (I did the wrong thing last year and did not take the advice given here due to time constraints).

Trying to buy things early this year so I have it when I go to open my pool here soon. Long story short: I have a small air leak on the suction of my pump at the threaded connection on the housing. It was suggested last year to use a "pump union" instead of just threading in a 1 .5 MPT pvc fitting.

So, I think I found what I need, but of course now I have two options:

1. Hayward branded pump union - https://www.amazon.com/Hayward-SP14953S-2-Inch-Socket-Female/dp/B0038ER6VG
2. 3rd Party branded pump union such as https://www.eztestpools.com/super-pro-1-5mptx1-5s-self-sealing-union-with-o-ring-21063-170-000/

The Hayward part does NOT have a gasket on it, but it is cheaper and I get free next day shipping on Amazon.
The 3rd party brands all have a gasket to seal against the pump housing, but all are all at least double the price of the Hayward fitting.


My questions are:
Can I just get a gasket to fit on the hayward fitting?
Should I just go with the ones with gasket included?
Is there some other option I am missing?

Thanks,
Matt
 

mts37

Bronze Supporter
Sep 20, 2016
33
Whitehouse Station, NJ
According to this Parts Sheet that Hayward union includes an o-ring. I don't see how a PVC union could work without some kind of gasket / o-ring.
I believe the o ring on that parts list is the one in between the union halves. Someone even asked about a gasket against the pump housing in the Amazon Q&A and Hayward responded to just use thread tape.
 

crusemm

Gold Supporter
Bronze Supporter
Sep 1, 2011
412
North Texas
If your talking about the pump side where it connects to your pump casing, those connections are NPT and don't take a gasket. Use Teflon tape, Per the Manual on page 5
"Plumbing Use Teflon tape to seal threaded connections on molded plastic components. All plastic fittings must be new or thoroughly cleaned before use. NOTE - Do NOT use Plumber’s Pipe Dope as it may cause cracking of the plastic components. When applying Teflon tape to plastic threads, wrap the entire threaded portion of the male fitting with one to two layers of tape. Wind the tape clockwise as you face the open end of the fitting, beginning at the end of the fitting. The pump suction and outlet ports have molded-in thread stops. Do NOT attempt to force hose connector fitting past this stop. It is only necessary to tighten fittings enough to prevent leakage. Tighten fitting by hand and then use a tool to engage fitting an additional 1 ½ turns. Use care when using Teflon tape as friction is reduced considerably; do NOT over-tighten fitting or you may cause damage. If leaks occur, remove connector, clean off old Teflon tape, re-wrap with one to two additional layers of Teflon tape, and re-install connector."
 

Pool_Medic

In The Industry
Apr 1, 2018
1,530
Bangor Maine
Most mpt x slip unions will have an o ring inside the fitting as well as one on the mpt threaded end. No plumbers tape is required on the threaded end because when you tighten it to the suction end that o ring seals it.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
22,629
Bedford, TX
Matt,

I am a little late to the game here, but I agree 100% with the medic...

Pump unions do not need anything on the treads because they have an O-Ring on the threaded end. Obviously, they also have an O-Ring between the two halves of the union..

Thanks,

Jim R.
 

mts37

Bronze Supporter
Sep 20, 2016
33
Whitehouse Station, NJ
I hear what you are saying @Jimrahbe and @Pool_Medic but the standard pump union made by Hayward does not have an o-ring on the threaded pump connection. The “other” brands do. See photos attached.

as @crusemm notes even the manual for the pump says to just use tape on the threads. I like to buy oem parts when possible, but am wondering if the o ring is really necessary or not.
 

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Pool_Medic

In The Industry
Apr 1, 2018
1,530
Bangor Maine
That image might not be showing the o ring, I’m not sure I don’t buy Hayward fittings. I do know that every threaded Union I use has an o ring. The issue with plumbers tape is at time not enough or too much is used, then the average DIY’er would attach a wrench and over tighten it. Every fitting for unions just requires hand tightening to form the seal by the o ring. Over tighten and something is going to break. It’s one reason I always have lube handy to insure o rings are pliant.
 

JamesW

TFP Expert
Mar 2, 2011
27,062
I don't think that the Hayward union comes with an O-ring. The Hayward is also not heat resistant.

I would get one that comes with an O-ring and one that is heat resistant.

CMP high temp unions are a good choice.
 

crusemm

Gold Supporter
Bronze Supporter
Sep 1, 2011
412
North Texas
Most mpt x slip unions will have an o ring inside the fitting as well as one on the mpt threaded end. No plumbers tape is required on the threaded end because when you tighten it to the suction end that o ring seals it.

Matt,

I am a little late to the game here, but I agree 100% with the medic...

Pump unions do not need anything on the treads because they have an O-Ring on the threaded end. Obviously, they also have an O-Ring between the two halves of the union..

Thanks,

Jim R.
I don't dispute anything you said, However the Hayward pump manual says to use Teflon Tape, and the Fitting from Hayward comes without an o-ring. Looks to me that by design there is supposed to be installed with no o-ring and that Teflon Tape is supposed to be used on the threads. All that being said, using a different fitting with an o-ring that seats properly and seals the joint would be perfectly acceptable also. @mts37 it's your choice. You've been given the tech manual, the options, and the advice of experts (not me) so now it's up to you.
 

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