Increasing flow rate from shower

[Nick Allen]

Hi, we are in the process of refurbing our bathroom and ensuite. We get ok flow rate in our bathroom of 10l per min but only get 5l per min in our ensuite.

System is a gravity fed system. We can’t increase the flow rate too much as we have a tank that is only about 100l.

Anyone know how to increase the flow rate in the ensuite to about 10l per min?

Thank you.

 

[cross thread]

what hight from shower head to cold storage tank

 

[Nick Allen]

About 2m. It has to go about 3-4m horizontally if that makes a difference.

 

[dishman]

I went through this process not too long ago. If you want to avoid pumps, it is possible, just but depends on a few factors.

https://www.diynot.com/diy/threads/ball-a-stop-isolation-valve-easy-to-swap.474279/

That was the thread.....you may find it an interesting read.

It starts off about isolation valves, but then I start to look at the shower I pretty much look at all the options.

There are also some good links in it to sites that help with low pressure systems with low flow. Edit: The links I found useful are here:

http://www.johnhearfield.com/Water/Water_in_pipes2.htm

http://www.forest.plumbing/why-your-water-pressure-might-be-low-part-2/

 

[cross thread]

could you raise the height of the cold tank to give more head

 

[dishman]

"give more head"

.....I'll get my coat

 

[Nick Allen]

Thanks for that. Just read that thread.

What would cause the difference between the two showers we have, one 10l per min and one being 5l? Is it the horizontal distance (difference about 2m) or could it be the shower itself? Both are Gainsborough mixers but the 5l one looks quite a bit older.

Also if we were to install a pump, can you adjust the pump settings to limit the flow rate?

Thanks, appreciate the help.

 

[Nick Allen]

Unfortunately,can’t raise the tank any higher

 

[dishman]

If I were to guess, as it is a modern bathroom, I bet the mixer has ceramic washers. These will hugely affect the flow. They are designed for high pressure systems only. Some say "high and low pressure" but they only mean they will technically "work just about" with low pressure.

You really need the multi-turn rubber washer type shower mixer. I could only find this in an Victorian/Edwardian style. Pain the the stylistic bum if you have gone for a modern look.


I also wonder if the pipework is 22mm to the new bathroom. I bet the plumber may have used 15mm for both supplies. As per my post I think that I mentioned, via the information on that link that 1m 22mm pipe has the same resistance as 7m of 15mm pipe.

Both those things will affect the flow a lot.

I added the two useful links to my original post they are both very useful.

-----

As far as I am aware, the pump has a specific output, I am not sure if they are variable. You have to try to balance this with the cold with a pressure reducing valve if you just pump the hot. The contributors to my post go into detail on that.

Is your cold mains fed? How big is the cold water tank in the loft?

 

[Nick Allen]

Sorry it’s taken a while to reply. Pipes are 22mm out of the cylinder then it splits and changes to 15mm, so runs at 15mm for about 2/3m. It’s at 15mm for less than a metre to the better shower.

Looks like the cold is fed from the tank. It about 850x500x600. The tank feeds the cold supply to the shower.

 

[dishman]

So both your cold supply and hot supply are low pressure? Based on those measurements your cold water tanks stores about 255litres.

An easy way to test this is if you use the cold water, do you hear the tank re-filling?

 

[Keithmac]

You can buy showers with built in pumps, Redring do a couple.

 

[Nick Allen]

Just ran the cold and the good shower is at 6l per min and the bad shower is at 3l per min.

Ran the hot again and that was about 8l per min and 4.

The kids had a bath about an hour ago, would that affect it?

Yep. Can hear the tank refilling when using the cold.

Thanks

 

[Nick Allen]

Can you get a mixer shower with a built in pump?

Trying to avoid an electric shower if possible.

 

[dishman]

Because you have both feeds at low pressure, it is much more simple to pump the supplies for both as per the advice is my thread. A pumped power shower (not electric) will do this.

For me that was less of an option because my cold is at mains pressure and hot is low pressure so there was too many issues in trying to balance them.

I also could switch to low pressure cold because the cold tank is pretty small.

Remember your cold tank will drain twice as quick as the hot tank because it is feeding the hot and cold.