switching from cold water tank to mains

[iep]

We have a cold water tank in the loft of our house that provides cold water for our bathroom and toilet room via a single 22mm pipe. It also provides the water supply to the the hot water cylinder (traditional copper cylinder) via a seperate 22mm pipe.

For a number of reasons, it would be useful to boost the cold water pressure in the bathroom. To do this I am considering disconnecting the cold water tank feed and hooking up the bathroom's supply directlty to water main. This would be a very simple modification to make as these pipes run close together through the airing cupboard.

For clarity, I would not be removing the cold water tank feed to the hot water cylinder as I understand that the cylinder would not be able to cope with mains pressure water.

So, the cold water pipe work ot the bathrrom and toilet is all copper (soldered) and provides water to two sinks, the bath and two toilets. If I were to connect this pipework directly to the mater main is it possible that damage would occur?

The pressure from the tank is only about 0.3-0.4 bar so a move over to mains pressure would be a big step up. I guess the taps might be able to cope but I'm concerned as to whether the toilet flush mechanisms will be up to the job.

Can anyone comment on this?

iep

 

[kidgreen61]

Shouldn't be a problem- go for it.

Be sure to check that you don't leave any pipes going up tothe loft open, or you will have a flood on your hands!

 

[iep]

So, no danger of exploding cisterns you think?

If this is a goer then it would fix many issues in our bathroom (toilet takes an age to refill, can't rinse out sink as water is too low pressure etc).

I'm keen to proceed but am still a bit nervous as it all seems a bit too simple.

ip

 

[pmx_super]

Generally speaking I gather having unbalanced supplies isn't a good idea...

Is there a shower in this 1 bath, 2 sink, 2 toilet bathroom? If you supply cold from mains and hot from a gravity fed system you'll be in for some pretty cold showers unless you get a venturi shower mixer.

You could also be in trouble with the cold mains pushing it's way back up into the hot water system if you have mixer taps.

 

[iep]

I was wondering about that. As it happens the next step in my plan is to go for a fully pumped shower. I prep for this I was planning to install a simple thermostatic shower mixer that claims it can cope with up to 5:1 pressure imbalance. I figured that would probably be enough?

BTW, what is a venturi mixer? Is venturi a type of mixer or a brand of mixer?

Cheers,

iep

 

[Rico99]

iep,

Venturi is a type pf shower. It uses the pressure from the cold mains to "drag" the hot water through at an equal rate.

Take a look at the below for example.

http://www.shower-guide.com/venturi-showers.htm

Rico

 

[pmx_super]

I was wondering about that. As it happens the next step in my plan is to go for a fully pumped shower. I prep for this I was planning to install a simple thermostatic shower mixer that claims it can cope with up to 5:1 pressure imbalance. I figured that would probably be enough?

BTW, what is a venturi mixer? Is venturi a type of mixer or a brand of mixer?

Cheers,

iep

If you're going for a pumped shower you should just get a twin impellar pump and pump both hot and cold gravity feeds. The mixer you found should protect against the pressure difference problem, but won't guarantee a decent showering experience.

 

[iep]

Thanks for the responses. Rico, really helpful site for the venturi explanation.

I should explain that I already have an RSP75 shower pump waiting to be installed. This will pump both the hot and cold supplies to the shower. The hot will be taken from the s-flange on the cylinder and the cold directly from the cold water feed from the cold tank (which I would plan to recommision for the purpose).

However, this is a big job due to the requirement to lay a load of new pipework under several floors and I am planning to do it as and when we relay these floors (may be some months).

Additionally, according to the good peopl of slamader tech help, I don't want to go using the pump to pump cold water to the other parts of the bathroom (toilets etc).

So, the final plan would be:

1. Existing gravity fed hot water to the sinks.
2. Pumped hot and cold water to the bath/shower mixer.
3. Mains presure cold water to the sinks and toilet cisterns.

Interim plan would be:

1. Existing gravity fed hot water to the sinks and bath.
2. Mains presure cold water to the sinks, bath and toilet cisterns.

So the only two questions would be:

1. Will I need new float valves of rthe toilets (maybe)?
2. Will I be able to use a thermostatic mixer on the bath/shower with the cold at mains pressure and the hot water at gravity fed pressure?

Sorry for the long post.

iep