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Urgent Hlep !!! Shower pump/water pressure problem

Postby hope-park » Fri Mar 23, 2007 10:38 am

I have recently refurbished my bathroom and problem arise, just wonder anyone here maybe able to get me some advice.

I have a indirect system in my flat. Basically, the cold water from the main feed the water tank and the water tank feed the hotwater cyclinder.

Because of low water pressure, I installed a shower pump. The cold input to the pump is from the water tank, and the hot water input is from the hot water cyclinder. The pump is working but, once I have the shower turn on for about 2-3 minutes, the water pressure drop down, and I have to turn off the shower for few second and turn it back again in order to get water presssure work properly again. Can anyone here know what is the problem ???

My next problem is the cold water pressure to my basin. The basin mixer tap cold inlet is direct from the water tank and hot inlet is from the cyclinder.
It work ok before the pump was installed. Now, even the pump/shower is turn off, the hot water work ok but the cold water is lower than we have before. The hot/cold supply to the mixer tap have nothing to do with the shower pump, it is exactly the same connection as before. The shower pump only connected for the shower, I don;t know why this doesn't work properly.

Please, I need help..

Many thanks.
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Postby dancbr900 » Fri Mar 23, 2007 11:54 pm

How Big is your cold water tank?
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Postby bernard » Tue Mar 27, 2007 12:04 am


I have the same exactly the same problem I hope someone has some ideas.
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Postby hope-park » Wed Mar 28, 2007 10:15 am

Thanks. The water tank is about 1.2mx1.2x1.2m. I think it should be big enough for a small 2 bed flat with only only bathroom.

I have a look on the hot water cylinder yesterday. It is a an unvent water cylinder, because it unvent, when the pump on, it suck the hot water out the cylinder and the cold water from the water tank may not be fast enough to feed the cylinder, because no air can go in to the cylinder, the amount of hot water that can flow out the cylinder will be affected as cold water is not fast enough to feed the cylinder, therefore it cause a slow down in water pressure.

I have a mixed tap for my bath, I try it with just cold water, the pressure seem to be no problem, but when i mixed it or turn to hot water alone, the pressure drop after few minute. So, I suspect mayb this is where the problem coming from.

Any one have an idea of easy way to solve this problem.
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Postby peter the plumber » Wed Mar 28, 2007 3:56 pm

This is so funny

Ok folks your cylinders only hold about 115 litres of hot water, your shower pumps run at about 15-40 litres a min.

So you only have about 10-3 mins of hot water before you run out.

The reason for your pumps dieing is that they are just running out of water.

You if have a look at your shower pump instructions it will tell you how much water your pump usages per min.

You would have been better off fitting unvented hot water systems, which run at mains pressure (3 bar) and gave about 6 hours hot continuous hot water.

Has for the taps, there just clogged and need a good clean or just in need of replacement.
peter the plumber
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Postby DONFRAMAC » Sun May 06, 2007 12:09 am

HOPE - PARK quoted his system as indirect hot cylinder fed from header tank above. This tank measures 1.2 metres cubed, which gives a volume of 1646 Litres if brimmed, =362 uk gallons, = 452.5 US Gals. The indirect cylinder in a cupboard below is likely to be the E 7 volume, 210 litres, = 46.2 GB gallons. Using the maximum pumping speed quoted, of 40 litres per minute, gives 5.25 minutes of very hot water, blended with cold water at a minimum of 12 degrees centigrade, where I live. (Our local surfers have to brave 6 degrees Centigrade.) My Glow-worm Ultimate 40 BTU's/hour boiler can put out 72 degrees, and I once ran the hot cylinder at 65 degrees, but my twin-impeller pump was not continuously-rated, so after a year of coping with 3 showers back-to-back, it siezed up, so I by-passed it and run it on static pressure-head, much to the dissatisfaction of our Son when he is visiting. I find the head OK as I had the header-tank in the loft raised several feet when the central heating was installed, and renewed the tank. I would suggest fitting a continuously-rated twin-impeller power shower pump, and uprate your boiler output temperature, but avoid boiling noises in your boiler (tinkling). 65 degrees on the tank thermostat is as far as I would go. Another ploy is to change the insert in the shower rose, to one with smaller holes;--- My MIRA unit was supplied with a choice.
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Postby Reynoldspc » Sun May 06, 2007 7:32 am

It sounds like your CWS (cold water storage) tank isn't big enough. You are pulling the water ot of it with the pump faster than it can replenish itself. Check that there is a strong flow from the ballcock filling it back up as the water is used, sometimes debris from the main gets caught at the ballcock orifice restricting the flow.
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