Fitting a shower pump- where to get the cold feed?

[Lower]

I'm in the process of sorting all the bits to fit a pump to our shower system to improve the pressure. Currently the cold water comes off the mains and the hot water comes from a traditional unpressurised hot water tank and is controlled by a thermostatic shower temperature control.

The header tank for the hot water isn't huge and i know that pumped showers can use a lot of water, so can i use the current mains cold feed to feed the pump so that only the hot water is fed by the header tank?

Alternatively, can i use a single impeller pump and just pressurise the hot water and again use the mains pressure cold feed?

Thanks in advance.

 

[Softus]

I'm in the process of sorting all the bits to fit a pump to our shower system to improve the pressure. Currently the cold water comes off the mains and the hot water comes from a traditional unpressurised hot water tank and is controlled by a thermostatic shower temperature control.

In that case you have what are generally called unbalanced supplies, and the shower can't work properly.

The header tank for the hot water isn't huge and i know that pumped showers can use a lot of water, so can i use the current mains cold feed to feed the pump so that only the hot water is fed by the header tank?

No. Pumping the cold main is not a legal, practical or hygienic proposition.

Alternatively, can i use a single impeller pump and just pressurise the hot water and again use the mains pressure cold feed?

Yes you can. You would probably need to limit the pressure of the cold supply to match the pump, to get the best results. You can do this with a pressure limiting device, and adjust the dynamic pressure while watching the gauge.

However, be aware that you might need to increase the size of your cold storage cistern.

Yet another alternative is to replace the shower valve with a Trevi Boost, which is specifically designed to work on unbalanced supplies.

The best solution of all is a larger cold storage cistern, a twin impeller pump, and cold supply taken from the cistern, not the mains.

 

[Lower]

Thanks for your reply. I didn't know that pumping the mains wasn't practical or legal so i'll rule that out.

I'm struggling for space in the roof space where the storage tank is so i'd find it hard to fit a larger tank. Is there any reason why i couldn't fit a second tank (similarly sized) below the existing one and use the new tank to feed the cold feed on the pump and leave the existing tank to feed the hot water tank? Alternatively, could i just increase the feed rate to the existing storage tank by fitting a second ball valve?

Thanks

Richard

I'm in the process of sorting all the bits to fit a pump to our shower system to improve the pressure. Currently the cold water comes off the mains and the hot water comes from a traditional unpressurised hot water tank and is controlled by a thermostatic shower temperature control.

In that case you have what are generally called unbalanced supplies, and the shower can't work properly.

The header tank for the hot water isn't huge and i know that pumped showers can use a lot of water, so can i use the current mains cold feed to feed the pump so that only the hot water is fed by the header tank?

No. Pumping the cold main is not a legal, practical or hygienic proposition.

Alternatively, can i use a single impeller pump and just pressurise the hot water and again use the mains pressure cold feed?

Yes you can. You would probably need to limit the pressure of the cold supply to match the pump, to get the best results. You can do this with a pressure limiting device, and adjust the dynamic pressure while watching the gauge.

However, be aware that you might need to increase the size of your cold storage cistern.

Yet another alternative is to replace the shower valve with a Trevi Boost, which is specifically designed to work on unbalanced supplies.

The best solution of all is a larger cold storage cistern, a twin impeller pump, and cold supply taken from the cistern, not the mains.

 

[Softus]

Is there any reason why i couldn't fit a second tank (similarly sized) below the existing one and use the new tank to feed the cold feed on the pump and leave the existing tank to feed the hot water tank?

An unusual idea, but I don't see why you couldn't/shouldn't do that.

Alternatively, could i just increase the feed rate to the existing storage tank by fitting a second ball valve?

It's unlikely to make much difference to the incoming flow rate.

 

[NoPoke]

Do you really need a pump?

my shower head is a low pressure unit fed from the cold tank which is no more than 2 feet above the shower head.

So do I get decent flow from the shower? Yes and No. Yes after I've cleaned the shower head, No after the inevitable buildup of limescale and silicone grease that keeps the shower head and mixer mechanism working.

It is truely remarkable the improvement in flow after the shower head is properly cleaned.

I have no idea how good the venturi based boost system are (Trevi). I thought there was an impeller based pressure balancing boost device too but can't find a link. In addition I don't know what the water regulations have to say about equipment like shower mixer valves that can introduce silicone grease into the cold water supply.

 

[Lower]

The simple answer to that is that i don't know.

We have good mains pressure, and approx 1.5m head from the water tank to the shower head.

We have a downstairs shower already which is gravity fed and has acceptable pressure, but my wife wants a power shower and consequently that's what i will install. Its not worth the hassle of fitting a shower, finding the pressure isn't good enough and then fitting a pump.

Hence i want to do the work now whilst i'm fitting the new bathroom and not retrofit a pump at a later date.

Power is already there because there is an electric shower in place that i will be removing and the hot water tank is right behind the wall that will have the shower mounted on it with the water storage tank directly above so its an easy install.

Once i've made sure there is enough water storage.....

 

[Rico99]

Lower,

Seriously, Look at the Trevi as mentioned by Sofus. Mutts Nuts as far as I am concerned.

Shower Pumps are noisy lumps with more working parts and sensors to go wrong.

Fit a Trevi, you would only need to get the hot supply to it as it uses the pressure from the cold main to draw the hot thru the shower faster.

Rico

 

[NoPoke]

Okay so the requirement is for a system with a pump and not just a working shower.

How big is the current header tank?
How much flow are you planning for this power shower?
have you already decided upon or bought the shower head assembly?

One of the reasons for having a large header tank to feed a power shower is to avoid the possibility of the pump running dry. With a really powerfull shower pump you also have to ensure that you don't get cavitation on the inlet side as there will be a pressure drop in the pipework that feeds the pump. The pressure will already be low due to the lack of head. Installing a second tank below the first will reduce the head further.

Perhaps the best reason for not installing a second tank below the first is that once the whole system is connected you will have a flow path from the high header tank via the pump and mixer backwards through the other side of the pump into the lower header tank. A situation that can easily result in the lower tank overflowing. You can fit one way valves but personally I only trust them to restrict the reverse flow of water rather than eliminate it . Even if they do initially work with the inevitable limescale build up I would expect the valves to leak at some point in the future.

 

[Lower]

I have looked at the Trevi system, but its not compatible with the type of shower that my wife wants (its a cosmetic thing....)

Lower,

Seriously, Look at the Trevi as mentioned by Sofus. Mutts Nuts as far as I am concerned.

Shower Pumps are noisy lumps with more working parts and sensors to go wrong.

Fit a Trevi, you would only need to get the hot supply to it as it uses the pressure from the cold main to draw the hot thru the shower faster.

Rico

 

[Lower]

Current header tank is 25 gallon.

Don't know what the flow rate would be yet. I'm provisionally planning to use a salamander 1.5 bar twin impeller pump.

I haven't purchased any of the shower related equipment yet. The bath suite has been ordered but i'm in the planning stage for the shower set up.

That is a very valid point about the tanks cross filling via the mixer valve

I'm not looking to produce the most powerful power shower in the world, just something significantly better than we have installed in our downstairs gravity fed shower (installed last year and hardly used so no contaminant build up to worry about).

Based on previous experience, the height of the water tank above the shower head would not produce enough water pressure to meet with my wife's request for 'the sort of power shower we have when we visit friends in modern houses with power showers'.

The other option is to fit an indirect heat store cylinder and thus avoid the need for a pump by having mains pressure hot water. But at this point it seems the pumped option will be the cheapest and easiest to fit.

If my current cold storage tank is not big enough, i have the option of fitting a larger tank lower down in the eaves of the roof.

Okay so the requirement is for a system with a pump and not just a working shower.

How big is the current header tank?
How much flow are you planning for this power shower?
have you already decided upon or bought the shower head assembly?

One of the reasons for having a large header tank to feed a power shower is to avoid the possibility of the pump running dry. With a really powerfull shower pump you also have to ensure that you don't get cavitation on the inlet side as there will be a pressure drop in the pipework that feeds the pump. The pressure will already be low due to the lack of head. Installing a second tank below the first will reduce the head further.

Perhaps the best reason for not installing a second tank below the first is that once the whole system is connected you will have a flow path from the high header tank via the pump and mixer backwards through the other side of the pump into the lower header tank. A situation that can easily result in the lower tank overflowing. You can fit one way valves but personally I only trust them to restrict the reverse flow of water rather than eliminate it . Even if they do initially work with the inevitable limescale build up I would expect the valves to leak at some point in the future.

 

[NoPoke]

25 gallon is half the size of the tank fitted in our loft. From your opening post I was expecting something much smaller. I've just made a crude measurement on our low pressure shower: 4 litres / minute which gives an adequate but not invigourating shower.

Probably worth measuring the flow in your downstairs shower.

 

[Lower]

Measured it this evening.

Our downstairs shower gives 6L per minute. Upstairs gives 4L per minute.

Incoming mains pressure through the kitchen tap is 12L per minute.

 

[Softus]

I have looked at the Trevi system, but its not compatible with the type of shower that my wife wants (its a cosmetic thing....)

Could you explain this in more detail?

I'm not a Trevi Boost salesperson, but unless your wife absolutely hates this:

View media item 7366
...then one of the many configurations of this valve must surely suit you/her.

 

[ctp]

if you have enough hot water pressure to run your shower use a p e v of the mains water

 

[Lower]

I have seen this valve type, but my wife wants one of the classic overhead shower heads with exposed piping but one that also comes with a switchover valve that allows you to redirect the flow from the fixed head to a handheld shower head attached to a flexi pipe.

But thanks for your search

I have looked at the Trevi system, but its not compatible with the type of shower that my wife wants (its a cosmetic thing....)

Could you explain this in more detail?

I'm not a Trevi Boost salesperson, but unless your wife absolutely hates this:

View media item 7366
...then one of the many configurations of this valve must surely suit you/her.