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DIY submersible water heater, build your own water heater

***Be sure to use a GFI plug with this!***

here is a link to the Through-Wall version

 COPPER WARNING! most of the elements are made from nickel plated copper and should not be used!

I have not found stainless elements at Home Depot. Some of the Lowes stores have them.

A quick search on the web will find several types in the 240volt range.

Some links to try:

 1500 watt in the 120 volts stainless steel unit.


 here are some stainless steel options. they only make them in 4000 watt+ at 240 volts.


I've made a few changes to the heater parts list and instructions..


1500-5500 watt stainless element

12 awg cord

1-1/2" rubber coupling

1-1/2" reduced to 1" threaded

1-1/2" reduced to 1/2" threaded

1/2" water tight connector


Temp controller
















install the element into the 1-1/2" - 1" reducer.

...these are made to be inserted in one direction, so you will need to use a grinding wheel, or improvise, to remove the "stop" portion of the fitting.

some are sold with a round edge (pictured here) and some are squared (pictured above)

after removing the stop, connect the wires and install into the rubber coupler.





Here are a couple different

submersible options.

the top one has the wire ran inside the 1/2" irrigation "funny pipe" and fittings.

both work great!










I have used a heavy duty timer to control the temp. 15 mins on the hour will keep 300 gallons warm.

pex supply has thermostats

Use a GFI plug with this unit!





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alex batista said:

PEX controller doesn't come wired up ,so I used some scrap power cords.You may want to install a receptacle box underneath instead.

Pex controller mounted next to PH meter= fish very happy.Thanks for this Rob. Now I just need to work on rerouting all the power cords.

Hey Rob , I just wanted to say thanks. I built the heater and it works great. Fish are happy. I used it couple of weeks ago when we got down in 30's. Thanks again


What type of pH meter is that?  I don't think I've seen that brand before.  

Copper Warning!

the elements from home depot are made of nickel plated copper and should not be used.

after two seasons with my first unit, i can see that it is made of copper. we all know thats not good for fish.

here are some stainless steel elements i found. i plan to order a few and cut one to check if it is steel on the inside.

will keep you posted...


(if you have already built one of these, you may be ok for the season, just remove it asap, and replace with stainless next year. ... i plan to rebuild mine as soon as the new ones get here next week)

Nutradip continuous read .I've been checking the calibration weekly with my master kit and its been spot on every time.texas hydro sells them.

Nate Storey said:


What type of pH meter is that?  I don't think I've seen that brand before.  

Thanks for posting this, Rob.

Very useful and very clear instructions.

I do want to ask a question,

and if is has already been addressed

I hope someone will point me in the right direction:

"COPPER WARNING! most of the elements are made from nickel plated copper and should not be used!"

I know that copper is the traditional biocide in marine paints,

and it seems to do a decent job 

at discouraging both plants and invertebrates from growing 

on boat bottoms and submarine structures.

Yet humans have been drinking from copper pipes 

and cups and kettles since the Bronze Age.

And I'm guessing that very few of us are filling our fish tanks 

with water that has NOT travelled in copper pipes.

When I was raising angel fish commercially back in the 1980s

I found that the lead water pipes in my old house

interfered with the development of both eggs and fry.

After a house fire (arson, unrelated to the fish business)

I replaced all my pipes with copper

and my cichlids seemed happy and healthy.

So what is the real-life effect on fish and gardens

of heating and delivering water with copper pipes?

If the risks of low-level Cu-contamination are purely hypothetical,

we can save a lot of cost and effort 

by simply using domestic water heaters directly.


Cho, the problems with copper really arise when there is contact with copper surfaces in recirculating systems, and especially low pH recirculating systems.  I've had fish losses due to copper components in my systems (Zn as well).  It is definitely something to be cautious of.  If you are discharging water on a regular basis and running at higher pHs, the problem may not be as pronounced, but for continuous recirculation every copper component I've ever used has resulted in losses.

Ok, after much searching i may have found a 1500 watt stainless steel element. i have order a few of these and the 4500 watt units and will hack them open to see what they are made of and report my findings.

Thanks, Nate.

This is what I'm looking for;

real-life, current data.

Theory is important, but unless it is regularly compared to reality

it can quickly become venerated dogma.

My growing tanks are fed by a constant-trickle and overflow system

which effectively replaces a quarter of the water every 24 hours

and my water, though soft, has a pH of 8.0,

so I'm thinking that the use of a glass-lined domestic water heater

would not pose a copper hazard to these fish.

For that matter (and on a slightly different note),

today's household water heaters are so thoroughly lined with glass and plastic

(even the connecting nipples are lined with plastic)

that there IS no copper in contact with the water

so long as the elements are stainless or titanium.

I see that 4.4 kW on-demand heaters are selling for less than $200.

I wonder if they are available with stainless elements?

Perhaps it's a good morning for a bit of research...

Nate Storey said:

... for continuous recirculation every copper component I've ever used has resulted in losses.

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