Hello,

 

We have great water pressure (cold) coming in, but our water heater undoes all the good and we have the typical very weak shower as a result.

 

Thinking of replacing the water heater with a bigger one, increased wattage, but I'm not 100% sure if that will do the trick? Is there a way of telling what the "outlet pressure" of a water heater is?

 

 

Check hoses, check any filter /strainers in the fittings - in the hoses, inlet to the heater, in the shower spray. 

Replacing the heater is not the answer as all heaters have the same connection sizes. 

i guess by water heater you mean shower ??    the most common fault /obstruction can be found in the flexible hoses due to filter discs in the connections i have before cleaned these successfully     (truthfully binned them)

Very helpful!

 

I removed the filter and cleaned it. Water pressure improved a tiny bit.

I ran the shower with the filter out and noticed the strong water pressure going into the heater and ejecting through the hole where the filter normally sits.

 

The cold water faucet underneath our shower has a ton of pressure on it but it just vanished as soon as it enters the instant water heater.

 

It's not the shower head either, I unscrewed it and noticed minimal water flow coming thru the hose.

 

How does your setup control water flow?  Eg: mine has a valve that can be full closed to full open to the input hose.  It also has (had - I took it out) a flow control valve between the input hose and the shower unit.  Unless your shower unit is old and maybe full of calcium, it shouldn't hinder flow that much with valves open.

Ah I see, so the valve, even at max, is restricting the inflow and thus outflow?

 

 

Well, it shouldn't.  Is that in the full open position (max)?  And what's that other knob for?  If you have another valve at the front of the hose in, I would just remove that one (the one in the photo) from the line and see what you get.

Edited June 29, 20197 yr by bankruatsteve

I removed the "water volume" valve and noticed that even at "hi" it restricts the inflow. 

 

There's a taper. One end of the hole is narrower than the other.

 

I bored out the hole using a knife and now water flow is much better. Luckily water is still very warm too. 

 

Thanks for putting me on the right track.

Edited June 29, 20197 yr by Bassosa

There still maybe a filter disc where the shower connects to the house. 

Then fill the heater with vinegar and leave for a while.  

17 minutes ago, VocalNeal said:

There still maybe a filter disc where the shower connects to the house. 

Then fill the heater with vinegar and leave for a while.  

I have considered doing that.  But the only way I can imagine is to remove the unit and invert.  And then I think aagh.  Do you have a trick for doing that? 

I would bin the control valve filter and connect the hose directly to the heater, use the main tap to control the flow. 

OP, have you checked if there's a valve before the connection to the heater?

 

   

 

      

 

  

Edited June 29, 20197 yr by Isaanbiker

The "Hi-Low" is meant for adjusting the temp of the hot water input, if you have a cold season your showers will be cold also ???? 

The temperature of the unit is mainly controlled by the dial on the unit. The water flow also has major affect. Low flow HOT, high flow not so much. 

You can also try reversing the flow with the power off to see if there are any bits in the heater that can be flushed out.

I had similar and it was the copper pipes furred up with lime scale inside the shower heater, narrowing the pipes.

Either flush/soak in descaler or white vinegar and flush again.

Otherwise dump it and get a new one and be sure to descaler at intervals.

2 hours ago, bankruatsteve said:

I have considered doing that.  But the only way I can imagine is to remove the unit and invert.  And then I think aagh.  Do you have a trick for doing that? 

After draining elevate both hoses above the unit and pour messily down one hose until it comes out of the other.