Cracked heater manifold

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Rick T

Well-known member
Apr 28, 2019
139
Houston, TX
Both my neighbor and I are repairing the aftermath of the freeze that hit Houston. Both of us have a MasterTemp 400. Both of our manifolds cracked during the freeze. I removed the drain plug from mine so I have a drip every 3 seconds. His has a crack and sprays out pretty fast. We've tried all local pool shops, eBay, Amazon, and a few sites from a Google search. We are being told a minimum of a 2-month backlog. Any idea where else I can try?

MasterTemp 400 model number model # 460736. It'd the black piece that both the enter and exit pipes connect to the heater. Thanks.
 
I started a thread on this but now have stumbled onto this one. Both my neighbor and I have the same problem. Mine is a drip about every 3 seconds. His is spraying out. I bought some PVC elbows to make a bypass for now. Was thinking of taking the manifold off and trying gorilla epoxy on it while I wait like everyone else for months on places to get it in stock. Any other suggestions?
 
Rick T said:
Both my neighbor and I are repairing the aftermath of the freeze that hit Houston. Both of us have a MasterTemp 400. Both of our manifolds cracked during the freeze. I removed the drain plug from mine so I have a drip every 3 seconds. His has a crack and sprays out pretty fast. We've tried all local pool shops, eBay, Amazon, and a few sites from a Google search. We are being told a minimum of a 2-month backlog. Any idea where else I can try?

MasterTemp 400 model number model # 460736. It'd the black piece that both the enter and exit pipes connect to the heater. Thanks.
Click to expand...
Maybe try Inyopools.com

There was already a shortage thanks to COVID and now this has only exasperated things.

Edit: Is this what you are looking for? Pentair Manifold 400 (77707-0016) - INYOPools.com
 
Also I read the heater bypass thread. It is interesting. Are there any pros/cons of bypassing the heater whenever it's not in use? If I went months at a time without running water through it would the heater be prone to any mechanical issues like rust (humid climate of Houston), sensors going bad, etc? Thanks.
 
Rick T said:
Are there any pros/cons of bypassing the heater whenever it's not in use?
Click to expand...

Heater owners would confirm, but I would say less chance of scale (or corrosion to heater core) if chemistry was off (high or low). Otherwise, having water go through the heater helps to keep algae at bay unless the heater is drained well during the summer.
 
Rick,
I'm in Houston as well and have the exact same problem. The hairline crack on mine runs right along where the bolts are so I can't even glue it (assuming it would hold) . I have found if you run the pump at 1200 rpm the pressure drops enough to make my spraying water turn into slow leak. I would still rate the leak in "gallons per hour" but it's still better than gallons per minute.

I found out tuesday of this week that you need to pull the drain plug from your Filter, heater, booster pump, and both plugs from your main pump. You will then pop the top off your main pump and that should be enough to empty your system for freezing weather. My pool builder didn't teach me, a 90 second youtube video did. If I find a solution i'll follow up with it here.

Jake C.
 
There are two drain plugs on the MasterTemp. The one up front only drains the small forward volume of the manifold. You have to remove the front panel to get at the second plug which will let you drain the back of the manifold and heat exchanger. The rear plug is made of zinc typically.

If you can’t get the parts, then you need to cut off the flanges and install a PVC bypass or get a Jandy valve and a check valve and rebuild the heater plumbing with a valved bypass.
 

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That plug is where the optional pressure relief valve is installed.

The only drain plug is the black drain plug.

Pressure Relief Valve (PRV). Purchase separately and install (P/N 460925) a 3/4" pressure relief valve kit complying with the ANSI/ASME Boiler and Pressure Vessel Code, having a capacity equal to the Btu/hr rating of the heater.

Part Number 38674-0719 is just the valve. The Valve kit includes the brass pipe and is part number 460925.

In northern climates where they may be required, open drain cock located on the bottom of the manifold adapter, and drain the heat exchanger and manifold adapter completely. If heater is below pool water level, be sure to close isolation valves to prevent draining the pool (isolation valves are not required and should not be used on heaters installed above pool water level except when needed for winterizing valves).

Assist the draining by blowing out the heat exchanger through the pressure switch fitting with low pressure compressed air (less than 5 PSI or 35 kPa). Remove the Water Pressure Switch. Plug the port in the manifold to prevent bugs and dirt from getting into the manifold. Drain the plastic inlet/outlet manifold through the outlet pipe. If the pipe does not drain naturally to the pool, install a drain cock in the outlet pipe to drain the manifold.
Click to expand...


 
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Thanks. I didn't see the zinc plug. Do you know any downsides to putting in the Jandy Bypass mod and only allowing water to flow through the heater when it's operating? I heat the pool only a few times a year and the hot tub maybe 10 times a year. No idea if I would be extending or reducing the life of the heater and its components if I by pass it 99% of the time.
 
The heater uses a thermal regulator, which prevents water from going through the heat exchanger until the water heats up when the heater turns on.

When the heater is off, all of the water goes through the internal bypass.
 
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JoyfulNoise said:
There are two drain plugs on the MasterTemp. The one up front only drains the small forward volume of the manifold. You have to remove the front panel to get at the second plug which will let you drain the back of the manifold and heat exchanger. The rear plug is made of zinc typically.
Click to expand...
That second plug referenced (referred as zinc). Clear as mud that this drain cock referenced to be removed. Does the procedure state remove 2 drain cocks? The Procedure also states to remove the water pressure switch along with other steps.

JamesW said:
That plug is where the optional pressure relief valve is installed.

The only drain plug is the black drain plug.
Click to expand...
👍 (The zinc plug)

JamesW said:
The heater uses a thermal regulator, which prevents water from going through the heat exchanger until the water heats up when the heater turns on.

When the heater is off, all of the water goes through the internal bypass.
Click to expand...

Do you have the specific location in the manual that states that all the water bypasses the heat exchanger when heater is off or water temp is below temp set?

If this is the case, then running the pump during temps below 32 deg F would not protect the heat exchanger.

DBE6ADB7-BB3B-4761-BCA4-E1D968BC3C3A.jpeg
 
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The thermal regulator blocks the flow of water from exiting the heat exchanger.

So, when it's closed, water is blocked.

The purpose is to prevent water from going through the heat exchanger while cold to prevent condensation.

The thermal regulator is pushed into place by a spring, so some water might push by if there is enough water pressure.

The thermal regulator opens at 120 degrees Fahrenheit.

You are correct that the heat exchanger is not protected during freezing weather.
 
JamesW said:
The thermal regulator blocks the flow of water from exiting the heat exchanger.

So, when it's closed, water is blocked.

The purpose is to prevent water from going through the heat exchanger while cold to prevent condensation.

The thermal regulator is pushed into place by a spring, so some water might push by if there is enough water pressure.

The thermal regulator opens at 120 degrees Fahrenheit.

You are correct that the heat exchanger is not protected during freezing weather.
Click to expand...
at 120 deg it does open, all though not stated, it would not appear to be a fully open/fully closed switch. Perhaps I missed the statement that the heat exchanger is fully isolated when heater off or temp below 120 deg. Could you provide reference?
From manual and figure attached above:
“A thermal regulator and an internal bypass regulate the water flow through the heat exchanger to maintain the correct outlet temperature.”
- regulate mixture is implied?

If the heat exchanger was fully isolated wouldn’t that cause a potential dry or partial dry exchanger during fire resulting in possible damage?

thanks,
Cd
 
You make good points.

I don't know that the heat exchanger is completely blocked by the thermal regulator.

I suspect that some water might bypass, but I don't know how much.
 
In the pictures, the thermal regulator looks mostly closed. It is held in place by a spring, so it probably lets some water pass by pushing the regulator open some.

The purpose of the regulator is to reduce condensation buildup in the combustion chamber.

47-102-1453-xl.jpg


380000007s.jpg


6291-160.jpg


Pentair Thermal Regulator (38000-0007s) - INYOPools.com

"Your Source for Swimming Pool & Spa Parts With 40,000 Parts in Stock - INYOpools.com"
www.inyopools.com www.inyopools.com

 
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